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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: Monkey Uncle on January 17, 2018, 06:08:33 AM
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I'm interested in any recommendations you might have for a replacement carburetor.
'78 GMC K15 chassis/drive train with an '85 C10 body
Remanned crate 350 (stock) with less than 500 miles on it, mated to an old TH350 that came from a third (unknown) donor vehicle
No emissions control equipment other than pcv hose running from driver's side valve cover into front of carb
Original stock air cleaner from the '78 truck
Carb, intake, fuel pump, and all ignition equipment re-used from the old engine
Fuel pump and fuel lines appear new
The intake appears to be the original stock intake from the '78 truck, but the carb is not. The truck should have a 4MV quadrajet with divorced hot air choke, but it currently has a 1983 E4ME model with electric choke and several currently unused emissions features. I am having some idle and driveability problems that were not solved by a re-build (details here if you're interested: http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0)). It was better for a short while after the re-build, but now is even worse than before. While it might be possible for a quadrajet expert to get it running right, I don't have such an expert available to me, so I think it's time to quit fooling with it and just replace it with a carb that is better matched to an old 350 with no emissions equipment.
From searching various auto parts websites, I see that there are remanned 4MV quadrajets available from National Reman, United, and Autoline for what appear to be reasonable prices with a 1 year warranty. It also appears that there are several Edelbrock Performer and Holley Street Avenger models that are supposed to bolt on to my manifold, although prices for these are a good bit higher than for the remanned Q-jets.
Also my mechanic suggested that I consider a Carter aftermarket replacement with a manual choke. I wouldn't mind the manual choke, but my searches did not find anything manufactured by Carter. My understanding is that Carter is no longer in business, so any Carter carbs likely would be remanned, correct?
Any thoughts about any of these potential replacements? Or any other suggestions?
Thanks.
Edit: I should explain how the truck is used. It's a short distance errand/light to medium duty hauling truck. Not exactly a DD since I don't use it to commute and probably drive it less than a thousand miles a year. Although I like the cool factor of driving an old truck that is in pretty decent shape, it is not intended to be a show truck or a performance truck. So I'm interested in a reasonably priced carb that will get me down the road with a minimum amount of fuss.
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Rochester Quadrajets were generally bulletproof grocery getter carbs that ran for long stretches with not much in the way of issues.
The quality and care put into the rebuild job has direct bearing on how long it'll last. Driveablility issues could be several things. It could be as simple as the rebuilder didn't re-bush the throttle shafts or replace other worn internals. The core might've been jetted differently from the original unit and the rebuilder didn't bother to check specs. The list goes on.
Some 1978 Quadrajets were manufactured by Carter under license from GM. I replaced an original Carter 4MV Quadrajet on Dads' 1978 G20 Van with a reman back in the 80's. Was surprised to see CARTER, not Rochester, cast into both units. The being said Carter hasn't existed as a company since the late 1980's and manual chokes are a huge pain in the neck. I would steer clear of "New Carter carburetors" and manual chokes.
I'm not a huge fan of Holley carburetors on GM motors either. My Ford F250 with an FE390 has a Holley right from the factory but that's a different animal.
In order to get a 4MV manifold mounted choke Quadrajet in 1978 you had to buy at least a 3/4 ton truck.
The 1978 K10/K15 with 350 & AT should have a Rochester M4MC Quadrajet 17058503 or similar unit with a side mounted hot air tube choke. It could also have come with a Carter M4MC Quadrajet with the same style choke.
If you want a 1978 Rochester 4MV setup for very limited emissions and a manifold mounted choke you need to ask for a full ton chassis carburetor. The 1978 K30 with 350 AT came with a Rochester 4MV Quadrajet 17055698 or similar unit. If you can find a quality rebuilder that can sell you one of these I'd run it.
You're letting the truck sit for long periods of time so you should find "real" gasoline without the mandated Ethanol to corrode the carburetor.
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Thank you, hatzie. That was kind of my instinct on the Carter carbs when I did a search and didn't turn up much.
I left out a potentially important piece of information - the '78 truck originally had a 4-speed manual transmission. Not sure if that makes a difference in which carb model the truck would have been equipped with from the factory. At any rate, I believe the intake does have the well for the divorced choke (see photo). I have the old title for the '78 truck and have used the VIN to look up the specs - it definitely was born a 1/2 ton truck. I suppose it's possible someone could have swapped out the intake at some point.
I do use E0 gas. Expensive, but worth it.
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If you're only going to put 1000 miles on it per year, then i would just leave the carb on there and put up with the minor driveability issues; If you leave the truck sitting for a few days, having to crank about 10 seconds before starting is not TOO abnormal (i don't think?).
2) The "reman" carbs from national/United/Autoline etc. are likely JUNK----unless you don't mind taking them apart and checking them over---maybe (though they still could be junk), in which case, you might as well take the one you already have apart and rebuild it.....................
Generic remans
a) may not be put together with good care
b) tend to be rebuilt to general, one size fits all, specs vs. the specs for your particular application. Example: one part number may apply to a 78 monza with 305 AND a 78 3/4 ton truck with 350 and everything else in between........
3) Now, if you really think you need a new carb and are unhappy with what you got now, then:
http://www.jegs.com/c/Fuel-Carbs-Intakes_Carburetors/10271/10002/-1?N=1010271+4294961605+900555&Ns=P_PrimarySecondary%7C0%7C%7CP_SalesVolume%7C1&Tab=SKU
You may want to consider #15803
Summit has equivalent part numbers. i think these carbs may be rebuilt by JET and i think they are good quality rebuilds, unlike the 3 companies listed above.
i run the #15805 on the v-6 and it runs pretty good.
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Hi Stewart - the drivability issues are getting to the point that I don't want to put up with them any more (running extremely rich; erratic/rough idle, sometimes to the point of stalling out; poor cold weather performance; very poor fuel economy). I know these things should be fixable, but it's finding someone locally who is up to the task that is the problem.
I appreciate you sharing your opinions on the budget remanned carbs. I've read widely varying opinions of them in various forums and online reviews, which suggests to me that quality control is iffy. Maybe I get lucky and get a good one, or maybe I get one that wasn't put together right. Do you have first-hand experience with these brands, or know someone who does?
The #15803 model on the jegs website costs more than some of the new Edelbrock models, which makes me wonder if I should just go aftermarket.
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Ok, i admit that i did run a reman carb (i think it was National, but not sure. Whatever Pepboys carries..) on the 305, when i was running a 305 and it ran pretty good. So maybe they are not all "JUNK" so much as poor quality but more so they are probably not calibrated optimally to your specific application.
2) i'm not familiar with the Carter AFB (which is what i think the Edlebrock carbs are a copy of?), but knowing Edlebrock, they are likely very good quality.
http://www.jegs.com/i/JET-Performance/561/33009/10002/-1
Ok, it's a marine carb, but it should work just fine on the street? Also, it's calibrated for a 350. JET is high-quality.
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I was looking at the National website yesterday and noticed that they have "new" quadrajets for sale, in addition to the remanned carbs. I was scratching my head over that since Qjets haven't been produced for decades. So I called and spoke with a nice gentleman there, and he told me that they had some new Qjet castings made and built essentially new carbs from the ground up with all new internal parts. These carbs come with a lifetime warranty, and are priced competitively relative to the high-end remanned carbs sold by Jegs and Summit. Of course, even with all new components, the quality of the carb still depends on the knowledge and care of the person who assembled it. Do any of you have any experience with or knowledge of these "new" quadrajets?
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I don't have any info on the quality of the re-manufactured or new Quadrajets, but do have some other comments.
I initially tried using an Edelbrock 1406, which is a really common square bore replacement for these trucks. However, when I finally installed an AFR gauge and started playing with rods and jets from the Edelbrock kit, it always seemed to run too lean to get good performance. It was okay, but never quite right.
I then bought a junkyard Quadrajet off an '86 1 ton C30. Truck carburetors were updated later than GM cars, so this was one of the last models with no electronic controls. I bought a complete rebuild kit from Cliff Ruggles, including throttle shaft bushings. Once I rebuilt it and played around a little with the mixture and secondary engagement mechanism, I found it to be a great carb. With the stock jets and rods it runs at an AFR of about 13.9 most of the time, but I can watch it go richer (about 12-12.5) as I tip in the throttle and it goes to the secondaries. I also converted it to an electric choke and blocked off the hot air mechanism.
The only downside I have heard about the National rebuilt carbs is that the configuration is not always a good match to your vehicle. Its hard for them to do mass market re-manufacturing and still have the carb well matched to a certain vehicle. If you look at the specs for original Quadrajets, there is a lot of variation between vehicles.
Bruce
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Hi Bruce,
I've been looking at the Edelbrock 1405/1406 carb also. Not crazy about it as it clearly would be a retrofit exercise. I'm sure it would work o.k. for my non-performance application, but it kind of feels like the proverbial square peg in a round hole.
Do you know the model of the '86 qjet? Sounds like it is not an electronic carb, unlike my current E4ME.
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After doing a lot of poking around and getting a lot of off-line help from Henry (thanks Henry!), I realized that I had misidentified my carb model. It is not an E4ME, it is an M4ME. As I understand it, this is basically a normal Qjet with an electric choke, which should work fine on my engine. So I've been considering whether I can make this puppy work instead of springing for a replacement.
It recently had a standard auto parts store rebuild kit put in it (this was done by a local mechanic, not by me). I am not ruling out the possibility that something was done wrong during the rebuild. If it was rebuilt correctly, it clearly was not tuned correctly, or it has internal problems that were not addressed by the kit.
The biggest problem I'm having is that it is running way too rich, to the point where it smokes, blows soot, and the exhaust smells strongly of gasoline. So I adjusted the idle mix screws to see if I could get it to lean out. I know this is not a substitute for running through the full tuning procedure, but before I dive into that, I wanted to see if it is even possible to get it out of its rich condition.
I have never messed with the idle mix screws before. The engine was fully warmed up after about an 8 mile round-trip to the store. Based on instructions I've read, I was expecting to tighten each screw a turn or two until the idle started to stumble, and then I would back off. I actually was able to turn them all the way until they felt like they seated, and this produced just a little bit of burbling in the idle (turning one screw at a time, of course). Is this normal? I had anticipated that it wouldn't run at all, or would run very poorly, with one of the mix screws tightened all the way in. I only noticed slight variation in the speed and character of the idle throughout the range of travel of the screws.
At one point during the process, I revved the engine, and the rpms dropped down to a low idle. Apparently it had been stuck on high idle since the carb rebuild. I had noticed for a while now that it was idling pretty fast once it warmed up, but I had not been able to get it to drop down by goosing the pedal. Would adjusting the mix screws somehow allow it to drop off of high idle now?
After it was on low idle, I fiddled with each mix screw until the idle sounded best, which was about 2 turns out for each screw. But when I put it in gear the engine idled slow and rough. I increased the idle speed using the base idle screw, but still had to back the mix screws out to a total of 3 1/2 turns to get the engine to idle reasonably well when it's in gear. I couldn't get the idle to clean up completely - it's still kind of rough, but it doesn't seem to be in danger of stalling. I realize I should be doing all this with an RPM meter to get the idle set to spec, and should also be checking/setting ignition timing, but I wanted to see if the richness issue would respond favorably to adjustment before investing in more tuning tools.
The adjustments appear to have leaned it out some, as evidenced by lack of smoke and a reduction in the gasoline smell in the exhaust. But the exhaust does still smell like gas a little, and I noticed some soot blowing out when I revved the engine. I suppose it might just be blowing accumulated soot out of the exhaust system. Any good indicators I should be looking for to determine whether tuning has fixed or can fix this richness issue?
While doing all this, I noticed two other problems. The choke flap was only slightly open (see first photo) during the entire adjustment procedure, despite the engine being fully warmed up and despite it idling for probably 45 minutes while I was fiddling with the screws. Outside temp was in the upper 30s - chilly, but I would think that at that air temp, the choke should still be fully open after an 8 mile drive. After adjusting the mix screws, I test drove a few more miles and then parked the truck without looking at the carb. About an hour later, I went out and pulled off the air cleaner and the choke flap was almost fully open (see second photo). Is this choke behavior normal? If not, is there anything I can do to adjust it?
The second problem is that the OEM air cleaner is not seating quite right. It is about 1/16" to 1/8" off the gasket in the back. It is hitting a metal vacuum tube that comes up off the back of the intake and then turns and goes down toward the transmission (see close-up photo). Would it be possible to bend this tube slightly to get it out of the way of the air cleaner?
O.K., that's an awful lot - sorry for the long post. Any help is greatly appreciated.
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Hi:
First problem sounds like your choke rod and fast idle setting may be out of adjustment and/or you are missing a linkage or two that controls the position of the choke valve (flap). Sorry, I dont have a adjustment picture for the choke rod on the M4ME...maybe someone else does (usually comes with the rebuild kit). You may need to remove your choke housing to make the adjustments. Some time ago I think I sent you an exploded illustration of the M4ME...do you have this?....although this does not show how to do/check the linkage adjustments at least it will show you what linkages you should have on carb.
Second problem: yes, it is a close fit between the air cleaner housing and that vacuum fitting and distributor. My air cleaner has a "dent" in it to just make enough clearance. You can bend the metal pipe a bit backwards, as mine has this bend in it...just make sure you dont kink the line. Maybe you can replace the short little rubber hose at the bottom of the metal line with a longer one that can bend backwards a little more.
Regards,
Henry
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Hi:
By the way, can you post close up pictures of the front and drivers side of your carb?
Henry
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Hi Henry,
Yes I do have the M4ME diagram that you sent me. I studied the choke linkage parts, but I can't seem to match the drawing to the linkage parts that I'm seeing on my carb - they don't look like the same parts to me. But I don't have much experience with exploded parts diagrams, so maybe I'm just looking at it wrong. The first last picture below is a close up of my choke linkage parts.
When I operate the choke linkage by hand, the flap moves through its full range of motion, from almost completely closed as it was depicted in the picture above, all the way to fully open.
My rear vacuum break also looks different from the one in the diagram. Mine has two linkage attachment locations that are oriented parallel to each other. The one that is closest to the body of the carb is connected to the linkage that goes to the choke. You can see this black linkage in the second first picture. When I operate the choke by hand, the black linkage moves back and forth, but the linkage attachment on the vacuum break doesn't move - the linkage just slides back and forth along the slot in the linkage attachment. The other (outer) linkage attachment is supposed to connect to the secondary air flap, but the linkage is missing (this was pointed out to me in the previous discussion thread on my carb).
The third second and fourth third pictures are close-ups of the front and driver's side of the carb.
I tried bending the vacuum tube, but it wouldn't budge. It seems like the steel tube goes down through the short piece of rubber hose such that the tubing is inserted into the fitting in the top of the intake. The tube appears to be glued into the fitting with some sort of epoxy. Not sure what the piece of rubber hose is for.
(Edit: fixed incorrect photo references.)
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Hi:
Your older posts about adjusting the mixture screws to try and change high idle and richness of the engine are all abnormal. Lets start with the choke system: You are missing your primary vacuum break assy (front of carb on pass side). The vacuum connection for it is on the float bowl housing (big center body of the carb), front, top. You have a hose on this connection which runs to the back of the engine probably to the distributor...this is wrong. The hose from the distributor needs to transition to the metal hose (do you still have it?) and then back to another short rubber hose that plugs into a vacuum connection on the float bowl body, front, drivers side, low)....this is probably capped right now. The larger port on front, center of the float bowl housing is for the connection to the Evap Emission System cannister that may or may not be in your engine bay anymore...usually on the driver side fender well or maybe even on the front drivers side near the radiator...in any case you can leave it open for now if there is no connection. Secondly, from your photos, it appears as if your electric choke is incorrectly set...maybe as far as 180 degrees out. On the plastic cap, there should be a little pointer that should be pointing at the cast in hash marks on the front of the choke coil housing...you should be able to loosen the screws and turn it until the pointer comes to the middle of the hash marks. Thirdly, the rear vacuum break should have a vacuum hose that runs to the back of the carb...connection should be low down and maybe on the throttle plate (lower cast part of the carb) in the middle. There should be a long straight linkage from the primary vac break diaphragm to the link on the secondary throttle shaft on the choke plate (air horn or top cast part of carb). There should be a short link from the secondary vac break diaphragm to the same little link on the secondary throttle shaft. Then there should be a third linkage that goes from the secondary vac break diaphragm to the intermediate choke shaft, lever, and link assy...this is partially hidden behind the choke coil. I see you have a painted black linkage laying in there but I cannot tell what it connects to by your photos. Next, you need to connect the THERMAC vacuum hose to the connection that is below the choke coil...is this vacuum port there on the carb? From the photo on the drivers side, it appears you are missing the anti-dieseling solenoid...this is probably OK to leave this off for now...do you see a wire laying around to connect to it? Next, that pesky intake manifold vacuum connection behind the air cleaner: it should be a little T-port threaded into the manifold. The top connection (larger) goes to a short big rubber hose that the metal pipe connects to. There should be a side connection (smaller) that a rubber hose goes to that runs all the way over to the vacuum accumulator mounted on the firewall on the passenger side of the engine bay...it is a little round plastic can. It sounds to me that somebody broke the T-port threaded connection to the manifold and glued it back without the T-connection...you can buy one of these from one of the catalog websites. From the photos your carb looks like it is leaking from all the gaskets. Let me see if I can find a good straight on graphical image of how the M4ME choke linkages are supposed to be...maybe someone else on the forum can show what theirs looks like. While I was writing all this I was humming that old song by BJ Thomas: "Another Somebody Done Somebody Wrong Song".
Regards,
Henry
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I'll have to go from memory on all of this. Took the truck to the shop last night for a final valve adjustment on the new crate engine, as I was starting to hear some ticking. When the mechanic took the valve covers off, we saw that one of the rocker arms had slipped off of its contact point on the lifter. This is the second time this has happened, so I left the truck with him so he could replace all of the rocker arms (under warranty).
Not sure what's up with the primary side vacuum break. I've seen lots of photos and a few diagrams of M4MEs that don't have one, but who knows how those carbs have been butchered over the years. I have noticed that all of the photos I've seen of carbs that have both primary and secondary side pull-offs have the primary side pull-off connected to a vacuum fitting that does not exist on my carb. This fitting is in the air horn right next to the aneroid chamber (top front passenger side corner). On the photos I've seen of carbs with only a secondary side pull-off, this fitting is absent, as on my carb. But they all have the screw holes where a primary side pull-off could be attached.
Yes, that hose you're seeing that is connected to the fitting on the front passenger side of the float bowl housing is the distributor vacuum advance. I do still have the original vacuum advance tube, which could be used to connect the advance to a currently plugged fitting on the driver's side front of the fuel bowl.
I do not have a charcoal canister. Are you saying that the fitting for that should remain unplugged? Currently it has a rubber cap on it.
Yes, the choke was very badly out of adjustment, which is why it was not opening fully even after running the engine for a long time. I adjusted it yesterday and improved that situation some. Unfortunately the choke cover does not appear to have any reference marks on it (at least none that I could see through my bifocals). I set it such that the choke flap was open a small crack at an ambient temp in the low to mid 40s. This setting has it rotated about 70 degrees clockwise from where it was in the pictures above.
Prior to making that adjustment, I went through the checks outlined here: https://www.corvetteforum.com/forums/c3-tech-performance/1024531-q-jet-adjusting-electric-choke.html (https://www.corvetteforum.com/forums/c3-tech-performance/1024531-q-jet-adjusting-electric-choke.html). The measurements all seemed to be set to the proper specs. However, I wasn't able to do the suck test on the vacuum break. The hose attached to it didn't want to come off, and it seemed to be old and fragile enough that I was afraid I would tear it (I didn't have any replacement hose on hand - obviously I need to replace this hose at some point). But I actuated the vacuum break by hand and took the noted measurement, which seemed to be o.k. I'll need to check the function of the vacuum break once I get some replacement hose. (This also answers your question about whether the vacuum break has a vacuum connection to the carb - it does.)
I also re-set the fast idle screw to the base setting according to the directions at the link above. When I started the engine, I had to tweak both idle speed screws a little faster than the base setting. Yes, I know I need to get a RPM meter and set idle speeds according to spec, but for the time being I was just trying to keep the engine from running rough/stalling when I put the trans in gear. After setting the fast idle, I was able to get it to kick off by tapping the pedal. Previously it had wanted to stay stuck on fast idle.
Now the choke at least opens as it should after the engine warms up. Idle is still rough - not slow and lopey, more fluttery like it's missing. It's worse when the engine is cold, but even after it warms up some fluttering remains. Giving it any pedal at all eliminates the flutter - it runs smoothly while I'm driving down the road.
The rich condition appears to have been mitigated quite a bit. I think it is still running too rich based on the smell of the exhaust, but it is no longer smoking and blowing soot, and the exhaust doesn't smell as bad as it did before.
There is a linkage connecting the secondary vacuum break to the choke shaft assembly - it moves when the shaft assembly is rotated. As you noted, the link to the secondary air flap is missing.
Going from memory here, but I don't recall a vacuum connection below the choke coil. On my previous carb thread, one of the posters suggested that Thermac hose on the air cleaner should connect to the vacuum fitting on the rear center of the air horn. I haven't tried to make that connection yet. I will also need to find something to cap off the pcv inlet on the side of the air cleaner. The valve covers have been replaced with aftermarket covers (OEM covers wouldn't seal up right after the engine swap), and the new cover does not have a pcv vent on the passenger side.
You are correct that the carb does not have an idle stop solenoid. I've never had any issues with dieseling, so I'm inclined to forgo that part for now. I have not seen a wire in that vicinity, although there is a stray wire with a plastic connector on the end of it that comes from somewhere near the middle of the firewall.
The intake manifold vacuum port has the T connector, and the side connector is connected to a hose, but the hose runs toward the driver's side of the firewall, not the passenger side. Going from memory I can't recall whether it terminates in a plastic can. The top of the T connector does not appear to have a nipple on it - the solid vacuum tube is glued into the top of the T connector. The steel tube appears to run through the short section of rubber hose - not sure why the rubber hose is there at all, unless it was just left in place when the steel tube was glued directly into the fitting. I suppose the only way to remedy this properly is to replace the T connector with one that has the appropriate nipple for attaching a short section of rubber hose?
I snugged down all of the screws in the top of the air horn. They were all a bit loose; apparently the gaskets are still settling in from the rebuild. We'll see if this stops the seepage.
Thanks very much, Henry.
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Hi:
It is certainly possible that one variation of the M4ME did not have a front vac break diaphragm...maybe for cars...but I doubt it. That image from the Haynes manual I sent you should be exactly what was M4ME configurations for trucks....the Haynes guys know their stuff!
I think when you get your truck back you will see that the correct port for the front vac break is there on the front of the carb...you just have the wrong hose to it now.
Concerning the THERMAC hose connection, maybe I am confusing you with someone else who was wondering what the hose connection under the electric choke was for...anyway, look to see if it is there. If not, maybe it should be the plugged pipe on the throttle plate (front, pass side, bottom) of carb. How many vac ports do you have on the back of your carb (not including the big one that goes to your brake vac can)?
Evap Emission Control (EEC) port: OK, if you dont have the charcoal cannister anymore you should leave the cap on this port on the carb. It was used to send a vacuum signal to a valve in the cannister. I do not believe it was actually a vent for the carb.
PCV: You really should have this...you can do a search the forum to see where someone asked whether this was needed or not and a couple of us commented on the function of the PCV system. It was a couple of weeks ago on the "engine" section I think. The oem Chevy valve covers tend to get bent up and overtightened over the years so they do not seal properly...you can straighten the attachment points with a hammer and drift and if they are in such bad shape you can buy originals or aftermarket with the PCV holes. The Chevy oem valve covers and gaskets require a lot of attention to detail when installing such that you dont get leaks.
Vacuum connection at back of intake manifold: Yes, that T-fitting is supposed to have a top nipple (big) and side nipple (small). Short hose is supposed to slide over top nipple and then trans tube is supposed to slide into the short hose...I think this short hose allows the arrangement to bend over to the rear to allow your air cleaner housing to fit.
Choke and linkage adjustment: I think that some of those paragraphs from the Haynes catalog I will send you should straighten this out.
Regards,
Henry
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Thanks, Henry. I'll have to wait until I get the truck back to continue addressing most of these questions/issues.
Regarding PCV: the driver's side valve cover has a vent that is connected via the OEM hose to the appropriate port on the front of the carburetor. Is this sufficient, or should the passenger side be vented also? If the passenger side also needs to be vented, I'm wondering if I can get a vented cap for the oil fill hole, which currently just has a rubber plug in it.
In light of all the issues that we've identified so far, I'm again beginning to wonder if it's worth trying to fix this carb vs. replacing it. I could envision throwing several parts and a lot of work at it and potentially still having problems that can't be fixed. Do you think it would be worthwhile to go through the full, step-by-step tuning procedure without replacing any of the missing and potentially defective parts first? If that could mitigate the richness and fluttery idle issues, then I would feel more confident about replacing parts.
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Hi:
PCV: sounds like you have half of the PCV system installed. On the pass side valve cover is where you are missing a hole for an air inlet to the system...the original design had a valve cover with a hole at the back for this...and to keep the air clean coming in it had a metal pipe connecting to a little filter on the side of your air cleaner...so all this is missing. You really need it and the quick solution as you say is if you can find a combo oil filler cap-filter...I have never seen this but maybe it exists. And yes, you would need to plug the hole in the air cleaner. If you cannot find this combo filter, you just need to bite the bullet and get the valve cover with hole at back and get the metal tube, grommet and filter for air cleaner attachment...or just a valve cover with hole that has a filter attached to hole.
Carb decisions: I cannot determine if there is still something wrong inside your carb that buying choke parts and tuning up will not fix. My gut feel is that if the person that rebuilt your carb was the same person that installed the air cleaner stud, then I would not trust the rebuild...I would either rebuild it again myself or buy a rebuilt M4ME.
Regards,
Henry
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Do not over tighten the front 2 mounting bolts. Just snug. Will cause warping of the air horn.
Common for this to happen and can ruin the the sealing of the airhorn to the float bowl.
Can cause fuel to seep out around the top gasket.
If warped enough can cause air bleeds and fuel channels restrictions to be violated and destroy calibration and adjustability.
Too high a float level and or fuel pressure can also cause fuel to seep out around top gasket and accelerator pump shaft.
Would cause an over rich condition.
Front, Rear or both pull offs came on different applications, but you should not be missing any linkages as apparently you are.
Take the vertical 7 digit carb # from the drivers side of the float bowl and plug in google and see what comes up.
Can’t see your pics for some reason.
These remanufactured carbs can be very generic in calibration in an attempt to cover many applications which doesn’t always work. They can use a mix match of parts causing sealing issues also.
They were originally calibrated for specific applications.
You should be able to turn the mix Screws in all the way and almost or kill the engine if the idle circuit is calibrated correctly.
If the idle screw is turned in too far to keep the engine idling this will uncover the idle slots in the throttle bores.
This can cause the main feed system to draw fuel from the booster rings. The result will be over rich and rough idle.
You can see this by using extreme caution and looking down the primary(fwd) Ventures. There should be no visible dripping of fuel with the engine at idle.
For all tests or Adj the engine must be at normal operating temp with the choke fully open unless you are adjusting the choke system itself.
No vac leaks are imperative as well as a vac tight distributor advance can along with a tuned engine.
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Henry - thanks. I'll talk to the mechanic about the breather cap for the passenger side valve cover. He mentioned that he was going to get a cap for that side when he put the new covers on. I'll have to remind him. If he doesn't have it, it looks like there is an abundance of options available from the auto parts stores.
Blazer - thanks for the info. I have not attempted to tighten the mounting bolts, just the screws in the top of the air horn. They were all noticeably loose, and I just snugged them down with a manual screwdriver. But no telling whether someone else warped the carb castings over the course of the last 30-plus years. That's my major concern right now - the possibility that I might throw a bunch of parts and effort at the carb, and it still might have problems I can't fix due to being warped or otherwise having non-replaceable parts messed up.
Google doesn't turn up anything specific on the model number, but I have looked up the number on a couple of carb ID web sites and determined that it came from a 1983 Chevrolet with an automatic transmission. Can't really find anything more specific than that, so I don't know if it was originally calibrated for a truck application. Who knows how many times it's been rebuilt and whether the calibration is original. I don't know if the carb is a reman or not - it doesn't have a nameplate or anything that would identifying as coming from one of the big reman shops.
Prior to my adjustments, the idle mix screws were turned pretty far out (I forgot to count how many turns). So it sounds like the issue you described with the idle screws being turned too far in was not the problem. They are currently set at 3 1/2 turns out.
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There has been a lot of guessing and second-guessing in this thread, introducing some false data interspersed with accurate data. Based on the casting number, 17083226, the existing M4ME carburetor on your truck was produced for 1983 2WD and 4WD, 1/2- and 3/4-ton, Chevrolet/GMC trucks with a 305H engine, automatic transmission, federal emissions, and air-conditioning. The carburetor was manufactured without a primary choke pull-off (vacuum break). Whether or not the secondary air valve is actually missing a link requires a schematic breakdown and part number call out that is specific to that carburetor. Most such references are out of print. Although the carburetor's configuration lends itself to supporting a link between the air valve and rear vacuum break, that in itself is no assurance it should have one. An idle mixture screw adjustment of 3-1/2 turns out is typical and expected for this carburetor. The float setting should be 13/32" (10 mm). The accelerator pump rod in the inner hole of the lever is correct. One of the most chronic problems with QJ carburetors is float saturation, exacerbated by the introduction of enriched fuels. Bending of the fuel bowl cover is also a weakness in the design, but can be corrected.
OP, in a new unit of time, what are you wanting to accomplish - what symptoms are you trying to correct?
Edited for clarification.
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Thanks for that information, bd. Here are the symptoms I'm trying to remedy:
Running rich. I haven't had much run time with the truck since I made the mix screw adjustments and choke adjustments, so at this point I'm not certain how big of a problem I still have in this regard. When I get it back from the mechanic, are there any indicators I should be looking for to determine whether it is still running richer than it should?
Rough/fluttery idle. It is worst upon a cold start, but it is still noticeable when the engine is warm.
Not kicking down from fast idle. Again, I haven't had enough run time with the truck since the choke adjustment to determine the extent to which this problem still exists. I did get it to kick down after the adjustment, but I haven't tried enough to know if it works consistently.
Fuel seepage. When I get the truck back, I need to assess whether my screw-tightening did anything to fix this. I noticed it most around the accelerator pump shaft.
Beyond those symptoms, I'd also like to (1) figure out the best place to attach the vacuum hose for the air cleaner's Thermac system, (2) make sure distributor vacuum advance is hooked up to an appropriate port, (3) make sure the choke is adjusted appropriately, and (4) ensure proper routing and attachment of the transmission vacuum line to the manifold such that it doesn't interfere with the seating of the air cleaner.
Out of curiosity, where did you find the information on this carb model? If it is available on line somewhere, I'd like to download it so I have as much info about the specs as possible.
Thanks again.
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First pic is your carb. The rear pull off is required do to the type of airhorn installed and the 2ndary flap linkage hole is on the lower side of the the shaft. This requires the rear pull off. The lower link goes to the choke mechanism. The upper slot on the pull of goes to the 2ndary flap link hole I mentioned and is missing and should BE there.
When this type of air horn is used the front pull off is not needed nor has the vac port for it as you see in the pics.I’ve added some pics of different variations for you to study and you can see the difference when a front pull off is used and not.
I’m not saying this carb is set up as it was new. Due to the silver color it is Probably a reman and could have a mix of parts.
You can see the diff variations in the pics added
The only way to check the correct assy is to get these books pictured below and check each part by #.
Vol 1 should do it.
Also the later carbs past 78/79 have thinner and finer pitch threads mix screws with smaller holes under them than the earlier carbs so it is NOT uncommon to require 5 or more turns out as compared 3 or so for earlier carbs.
Everyone here is trying to help. There will be comments that could be wrong, misinterpreted, or type O’s.
There is no reason no matter how knowledgeable one is and contributes to this site that they should be insulting or otherwise in a demeaning manner.
A simple correction is all that is needed for the benefit of all.
(https://uploads.tapatalk-cdn.com/20180205/9047604f196b0545d6c141cfea721f1e.jpg)(https://uploads.tapatalk-cdn.com/20180205/ab9f7ccd78136b1fd3e9b92056b682c1.jpg)(https://uploads.tapatalk-cdn.com/20180205/180606ff67778e435bb751fbcd380bb9.jpg)(https://uploads.tapatalk-cdn.com/20180205/67060eb1d9514206a4a3db103faa25d3.jpg)(https://uploads.tapatalk-cdn.com/20180205/ed3d5e49cec1e956b82f698497dee3ce.jpg)
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Blazer, I was amidst amending my prior post when you responded. And your comment surprised me. No demeaning commentary or insult was/is intended, ever. So, if my post reads that way to you or anyone else, I beg your pardon. The point I was attempting to make, perhaps poorly, is that under the circumstances, to provide reliable 'help' to the OP requires a source reference that gives absolute and unrefutable information. The books you imaged are the references that would settle conclusively all parts and adjustment questions. Unfortunately, they are out of print. I discarded my volumes 20 some years ago and have rued the day many times since. I expended several hours today attempting to find them online, or a reasonable substitute, to no avail. I found partial breakdowns of the carburetor peripherals but none illustrating sufficient detail to support an absolute claim. Adjustment of QJ idle mixture screws can vary anywhere between 1-1/2 to 5 turns out. However, 3 to 3-1/2 turns is by far the most common setting for all M4M and E4M carburetors.
Monkey Uncle, if you decide to keep the existing carburetor I recommend checking the float for fuel logging as well as float level adjustment. Reiterating prior posts, a high fuel level can cause the fuel bowl gasket and accelerator pump plunger to seep as well as early fuel tip-in and dribbling from the main nozzles causing the engine to run rich. An electric choke should open fully within 3-5 minutes of engine running. If it doesn't, you will need to verify choke circuit integrity. If you haven't already done so, recheck the ignition base timing and spray for vacuum leaks before attempting any more carburetor adjustments.
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Blazer, thanks for the comparative pics. Those are very helpful in understanding the pull-off and secondary air flap linkage issues.
Bd, would fuel-logging be apparent by looking at the float?
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i have an 83 carb (because my truck is an 83) sitting on the shelf. i'm not sure what the casting # is, but i suspect it's in the same series because i was also originally equipped with the 305, AC, and automatic federal.
If anyone needs a picture of it, i can provide it, but not until the weekend. It's all original, not reman. And yes, it only has one choke pulloff.
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P.S.
i can't believe the tech at national concerning the "new" quadrajets until i see a webpage or other documentation. This is very bad business for a company representative to tell you that, i suspect.......
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P.P.S.
i'm going to go out on a limb and say that all your 4 major symptoms can be solved by getting the jegs/summit #15805.
2) Something is funny about your fitting on the intake for the vacuum modulator line to the trans. You may need a 90 degree fitting such as:
http://www.ebay.com/bhp/vacuum-intake-fitting
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Thanks for all that, Stewart. I'm interested in seeing a picture of your '83 carb, when you have the time.
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Bd, would fuel-logging be apparent by looking at the float?
The factory float is manufactured from lightweight nitrophyl closed cell foam. Give the float a gentle squeeze with your fingers and depress any blisters with a fingernail. If the float has absorbed fuel, it will ooze from the applied pressure.
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Stock Non-CCC quad off 83 1/2 ton:
(https://i.imgur.com/UOgRhcT.jpg)
(https://i.imgur.com/3tARniK.jpg)
(https://i.imgur.com/z6nG59C.jpg)
i can't help with where to connect the thermac----until next weekend IF we're lucky. But i don't think that is causing your driveablility problems, so it's not urgent.
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What's the carb number, Stewart? The secondary air valve link is installed. Can you post some clear pictures of it next to a ruler? A new link could be fashioned out of some appropriate diameter welding rod. The green Teflon coating isn't important.
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Will get on it asap, but very busy.
Also, apologize for the dirty table---that's not me, but again----very busy.
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Thanks very much, Stewart. Those pics are very helpful. From what I can tell, all I'm missing are the secondary air valve link and the idle stop solenoid. I don't think I'm having any dieseling issues related to the missing idle stop solenoid, so I'm not too concerned about that.
This might be the secondary air valve link: https://quadrajetparts.com/auxiliary-vacuum-brake-rod-fits-1980-3057-p-150.html (https://quadrajetparts.com/auxiliary-vacuum-brake-rod-fits-1980-3057-p-150.html)
Sorry I haven't followed up on this lately. The truck is still in the shop awaiting the replacement rocker arms. Hopefully I'll get it back later this week.
I think my first order of business will be to do as bd suggested and check for vacuum leaks. No point in going any further if the castings are warped and leaking. If that checks out o.k., next step will be dealing with the fuel seepage, and if I can get that taken care of, check timing, re-check choke function/adjustment, tune the carb, and replace the secondary air valve link.
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Just my .02 cents here, I would stick with the Qjet. Seems you are leaning that way. These other guys have given you some good advice, IMHO, and I know blazer74 helped me out when I was doing the build on my Qjet for my 454 using Cliff Ruggles forum and his book. I had previously tried switching to an Edelbrock 1407 & 1806. All gave minimal performance and really poor gas mileage. Tried a Qjet a couple of years ago from Nat. Carb., terrible experience. Sent it back within 3 days. You have a 1708 casting pictured, in my experience these rarely warp enough to cause problems. Those later carbs are somewhat thicker with a different bolt pattern up front than the earlier ones. From one of your pics of the front of it, warping seems very minimal to nonexistent. I have a couple 1708's in my garage, none warped. My orig. carb is a 1705 casting and was warped bad, but did not cause problems. I fixed warping just so it wouldn't get worse. Your wet air horn gasket tells me that the float level is to high and that alone can be causing your drivabiity problems, that and the APT may need adjustment also, but if the float is wrong it will be hard to get anything else right. It's a great carb., it just needs to be tuned for your engine if not the original. After learning about it, and taking some time to set it up with new good parts, mine runs great. Good luck.
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My very late reply to a question MonkeyUncle asked -
The carburetor I found on an mid-80's Chevy 1 ton pickup was the 17080213 M4MC, which is one of the last models with no electric or electronic controls. The truck had been owned by a local commercial company, and it looked like they had kept up all the maintenance. However, I am not sure if the carburetor was original.
I added an electric choke to replace the hot air choke, and also drilled and tapped it so that the APT could be adjusted externally. The rebuild kit I bought from Cliff Ruggles worked well, although I still ended up replacing a couple additional parts (choke pull-off, etc.) that appeared to not work correctly.
Bruce
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Thanks for the info, raf2330 and Bruce.
Raf2330, how did you fix the warping?
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I built a jig out of steel plate to mount the sections of the carb. onto. Applied pressure evenly in strategic places, as best you can, and put in the kitchen oven that I had set at about 250 degrees. Did each section of carb separately. Put the piece in for about 15 minutes to heat up, then would apply a little pressure to the bolts in very small increments as to not bend the parts to quickly and crack them or cause warping in a different area. Took a little over an hour per piece as I recall, air horn and main body were both real bad on mine. Trying to attach pics for reference. Hopefully it works.
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17083224
1873 FKA
(https://i.imgur.com/ovt0ikF.jpg)
(https://i.imgur.com/N7WTVkP.jpg?1)
Side closest to 2 goes to choke flap, side closest to edge of ruler goes to vacuum can.
2) Also important is that we must all fully understand and acknowledge that i normally don't keep such a dirty table; That was inexcusable and not my norm. Also, i don't drink that much Monster energy drink(which is also a bad habit), but i'm working nightshift now. :)
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Raf - wow, that's a pretty impressive fix. Unfortunately I don't have the fabrication skills or tools to pull off something like that, so if I do have warping issues, I'm probably looking at swapping out the carb.
Stewart - thanks for the photos. That's clearly different from the part that I linked to on quadrajetparts.com. Looks like their part is the link that goes to the choke, despite the web site saying that it is for the secondary air valve.
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This is the air valve link on the carburetor imaged by Stewart (#3056 (https://quadrajetparts.com/secondary-vacuum-brake-rod-fits-1979-3056-p-149.html) that replaces OEM #17062369 according to the Quadrajet Parts website). Perhaps if you call them, they can provide a definitive answer.
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Thanks for that link, bd. That does look like the right part.
FYI, I am still dead in the water due to the rocker arm issue, which also turned out to be a lifter issue. Hopefully I will get the truck back soon and can resume my carb troubleshooting. I'll post updates (and likely will have more questions) when I get into that.
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This Q J stuff will drive you nuts. just bite the bullet and buy a 600 cfm Holley with elec choke.
Problem solved.
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I finally have my truck back after a month-and-a-half detour to the shop, which resulted in all new rocker arms, lifters, and pushrods (all under warranty, thankfully).
The mechanic said he tweaked the timing a little, backing off the initial advance from 12* to 10*.
He also rigged up a fix for the transmission vacuum tube. I had bought a replacement T-fitting for it, but the mechanic said it wouldn't work because the original fitting supposedly is a "one way" fitting that only lets air move in one direction. Not sure if I believe that. At any rate, he epoxied over the broken off nipple on the top and attached the transmission vac line to the nipple on the side, disconnecting the 1/4" hose that had been attached to that nipple. The fix looks like crap, but it seems to work.
The hose that he removed was supposed to go to the vacuum accumulator can (I think), but I had never traced it to its terminus to be sure. Looking around now, I can't find anything that looks like a vacuum accumulator, so I'm wondering if that hose had just been hanging loose all this time, which would have created a huge vacuum leak.
The idle has smoothed out quite a bit; not perfect, but a lot better than it was. Not sure if it was the timing change, the vacuum hose fix, or something else.
When I got the truck back, I noticed that the choke wire was not connected. Upon reconnecting it the right way, I realized that it had not been connected correctly before, so the heating element probably had not been operating properly. With it connected the right way, the choke opened way too quickly and I was having a hard time with cold starts. So I rotated the choke cover counter-clockwise to correct the previous adjustment that I had done to it. It seems to be operating normally now, but I'm going to keep a watch on it to be sure.
Today I sprayed carb cleaner to check for vacuum leaks (throttle shafts, cracks between castings, and crack between throttle plate and intake). It idled the same throughout the tests, so I am assuming at this point that I don't have any major leaks in those locations.
It still runs somewhat rich, and it is still seeping fuel around the accelerator pump shaft. So my next step is to pull off the air horn and check the float and needle/seat. Question: when I do this, do I need to replace the air horn gasket? It is a new gasket, but it has gotten saturated with fuel because of the seepage.
Thanks, guys.
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Hi:
No, you can re-use a new air horn gasket if you let it dry out and it is still straight and not kinked or torn. When you have the air horn off and are inspecting/adjusting everything, you may discover you need to buy a replacement part so hold off on buying any carb parts until this inspection is done...the gasket may not be available as a stand alone part for sale anyway...may have to buy a whole gasket kit if you wanted it.
Regards,
Henry
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Thanks, Henry.
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I have the air horn off now, but I'm not seeing anything obvious that could be causing the richness and fuel seepage. I'm posting some photos in the hope that you guys might see something I'm missing.
The float was not too high; if anything, it was a little lower than the 13/32 spec. It was floating and does not appear to be leaking (brass float). I didn't hear any fuel sloshing in it, and nothing dripped out of it. The bowl looked to be about half full; not enough to close the needle. The truck had been sitting for three or four days, so it's possible the bowl could have drained or evaporated down some. There is some gunk in the bottom of the float bowl.
I couldn't see the needle well enough to tell whether it was seating properly when I pushed down on the float, but there was no gunk or anything in the seat that would have impeded it. In a couple of the photos below, I hung the needle back on the float the way it was hanging when I pulled the float out. Does that look correct? As far as I can tell, the needle appears to be in good shape, although I could see a slight circular impression on the rubber tip where it contacted the seat.
One of the brass tubes in the air horn appears to be slightly bent near the tip (far right tube in the picture).
The rubber ring at the top of the power piston appears to have some gunk on it.
The air horn gasket partly disintegrated and left behind some debris that will need to be cleaned off of the bowl and air horn.
What am I missing? Do you see something that might be causing the richness and seepage?
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More pics.
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The needle is in the correct position on the float. Personally, I would ditch the brass float, but there's always differing opinions on that. I'd change the needle if it shows any sign of wear at the seat since its apart. Stake ring for the power piston has seen better days, you can get a replacement for that also. They should have done it during rebuild.? You can try lowering the float level some if it is still giving you problems with seepage, as long as it doesn't go lean. I'm wondering though if you've checked fuel pressure? To much psi could cause the same problems I believe. Is APT adjusted correctly? The slight bend in the brass tube is ok as long as the diameter of tube is maintained.
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Thanks, Raf. I've been wondering if I should just go ahead and replace the float and needle while I have the carb apart.
I haven't checked fuel pressure - don't have a gauge. But I never noticed any fuel seepage prior to the carb rebuild.
I'm clueless on the APT. Do you know of any information sources I could consult?
Thanks again.
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Second on the brass float and float setting not too being to high.
You can get an sr kit from cliff which includes the float and entire acc pump assy.
The blue acc pump cups can be hit or miss with ethanol.
If you have no surging at cruise speed leave the APT alone.
Nozzle drip at idle can cause rich, rough and or off idle stumble as well as the mentioned fuel pressure.
https://cliffshighperformance.com/Quadrajet-rebuild-kits-and-quadrajet-parts/quadrajet-rebuild-kit-sr
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Thanks, Blazer. When you say nozzle drip, what are you referring to?
And another stupid question: Can I check fuel pressure without the engine running (i.e., by cranking the starter)? Or does the engine need to be running for the pump to make full pressure?
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Exactly what the name implies.
With the engine running at idle, completely warmed up at operating temp with the choke completely off.
CAREFULLY look down the primary bores and look for droplets of fuel coming from the booster ring nozzles on to the throttle blades.
Nozzle drip is caused by not enough idle fuel being supplied to the idle system and the fuel is drawn thru the main system to sustain an idle.
Idles rough and exhaust can stink.
Idle mixture screws not adjusted out properly not supplying enough idle fuel and/or the throttle blades are open too much exposing the transition slot with the idle screw can cause nozzle drip.
A heavy float or high fuel pressure can cause high fuel level in the bowl causing rich idle also and fuel seepage from the top airhorn gasket and acc pump shaft.
Brass floats can get a pinhole and fill with fuel hence heavy float. That’s the reason many don’t like brass floats.
That’s not to say a nitrophyl float can’t become fuel soaked also.
Cliff has a great book on quadrajets if your interested and a quad forum with a lot of info but can be slow moving sometimes to get a response.
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I prefer to plumb in a gauge and monitor the pressure. Engine compartment heat and heat soak can factor in also.
Aftermarket pumps can put out too much pressure from the get go. They even advertise 7-9 psi which is to much for a quad in my opinion.
You can do a volume test and vac/suction test on the pump but I’m not familiar with the specs but that won’t help you with pressure only volume.
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Blazer, thanks for describing nozzle drip. I will check for that when I get the carb back together and running.
Regarding heavy float, I read something on Cliff Ruggles' forum that suggests the brass floats are not as buoyant as the nitrophyll floats, even if they aren't leaking. Also, I re-checked my float level, and it appears I wasn't measuring accurately the first time. It is not adjusted low as I originally thought, but it is adjusted to the 13/32 spec, or perhaps a bit high at 7/16. So it still shouldn't be causing the bowl to overfill, but maybe so if the brass float is not as buoyant as a nitrophyll float? I'm finding it really difficult to measure to the nearest 32nd of an inch.
As long as I have the air horn off, I think I'm going to go ahead and replace the float, needle, and seat with quality parts from one of the Qjet suppliers. And perhaps accelerator pump and power piston bushing as well. No telling what was in the auto parts store kit that was put into the carb recently.
Next stupid question: The seat appears to require a 7/16 slotted screwdriver, which is a very rare animal. Local hardware stores don't carry anything bigger than 5/16. But I think I could order a 3/8 screwdriver on line. In your experience, is a 3/8 big enough?
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I have used a wide short craftsman screwdriver before.
I also have a flat blade apex tip I use.
I’ll have to look when I get home to see the size.
The only stupid question is the one that is not asked.
I threw in a pic for a pressure gauge.(https://uploads.tapatalk-cdn.com/20180325/420818b32f7aca0801bcaac1bd6135fd.jpg)
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Hi Monkey Uncle:
From your photos I do not see anything obvious causing the seepage or rich running.
The seepage could be caused by an assembly problem such as the float insert not seated flush or the float hinge pin not being oriented correctly. Also maybe the accelerator pump stem seal is missing or shot.
When you disassembled it was there a little pump well baffle in place on the float chamber floor by the accelerator pump?
Was there a big cylindrical insert in the aneroid cavity?
Yeah, you need a special flat blade tool to get that pesky needle seat out...I think I remember having a small scrap of sheet steel that I trimmed to size with some shears and the just used a needle nose vise grip to hold it and remove the seat. You may also just take a non-prized screwdriver to a grinding wheel and make it fit the seat slot.
Setting the float height is a little bit tough without being on the bench...when you call the carb guys to buy some parts ask them if they can give or sell you one of those paper gauges for setting float height...they usually come in the gasket rebuild kit. It usually takes me 3 or 4 re-checks to make sure I have it right when laying on the engine.
If you have the time, this is a opportunity to take out the two main jets to see what their part numbers are for future reference. You can use a standard flat blade screwdriver to remove both of them. Just make a note of what numbers are written on them. They are bronze or brass so be careful you dont strip them out or strip the slot...they are soft metal and just press down hard with your screwdriver and turn carefully and dont tighten too much on install. Make sure you dont get any dirt or FOD in the jet holes and passages. You want both jets to be the same part number and for them to be a size that was recommended for your carb and application.
Regards,
Henry
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I found a 3/8" slotted screwdriver locally, and it worked on the seat. Barely. A 7/16 or 1/2 would have been better, but those are hard to find. Once I got the seat out and could look at it up close, I could see that it had a very small piece of detritus in it, but that might have occurred when I was cleaning off bits of the air horn gasket. There is also a ring in the bottom where the needle rests - slightly different color like the brass has been polished. Not sure if that is wear or if it is just polished from frequent contact with the needle.
Henry - the pump well baffle appears to be in place, but there is no insert in the aneroid cavity.
I have a steel scale that is graduated in 32nds that I am using to measure float height. The main problems are not being sure I've got the needle seated when I push down, and not having a fixed point of reference on the float to measure (the float angles down, so there's a big difference in the measurement from the end of the float vs part way up).
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(https://uploads.tapatalk-cdn.com/20180325/a1cb6a610725bdf8d848c171a316553b.jpg)
Apex 7 flat works well inserted into a reversible screw driver.
The 3/8 is just big enough.
Lightly hold one finger on the needle and another on the hinge pin, use the other hand to measure at the toe of the float.
If you have an extra spring from the filter you can cut in half, place under the float while holding the hinge pin then measure.
Holding upside down is another way letting the weight of the float do the work while holding the hinge pin.
Don’t forget to put the metal ring back in under the seat and make sure only 1.(https://uploads.tapatalk-cdn.com/20180325/1d095a1f3d1305b831c4d23c9484703b.jpg)
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Hi Monkey Uncle:
Setting the float height is easier with that paper scale that comes with the rebuild kit...the scale has a white background and the graduations are in black...the paper scale is also a T-square and sized so it can fit in the float chamber and register on the top of the float chamber edge to make the measurement easier and more accurate. I can send you a image of where the measurement is supposed to be on the float arm.
Aneroid insert (stuffer): It appears to me the aneroid cavity has an open slot to the float bowl chamber so it would affect the volume of gas in the float bowl...my gut feel is that the insert should be there otherwise there will be excessive sloshing of gas and hence excessive movement of the float...maybe someone else on the forum can comment on this or maybe Stewart Griffin can open his M4ME carb up and see if there is a aneroid insert in it.
Regards,
Henry
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(https://uploads.tapatalk-cdn.com/20180325/a1cb6a610725bdf8d848c171a316553b.jpg)
Apex 7 flat works well inserted into a reversible screw driver.
The 3/8 is just big enough.
Lightly hold one finger on the needle and another on the hinge pin, use the other hand to measure at the toe of the float.
If you have an extra spring from the filter you can cut in half, place under the float while holding the hinge pin then measure.
Holding upside down is another way letting the weight of the float do the work while holding the hinge pin.
Don’t forget to put the metal ring back in under the seat and make sure only 1.(https://uploads.tapatalk-cdn.com/20180325/1d095a1f3d1305b831c4d23c9484703b.jpg)
Blazer, did you mean put back the rubber ring under the seat? Your photo appears to show a rubber gasket, and my carb appears to have a rubber gasket.
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Hi Monkey Uncle:
Setting the float height is easier with that paper scale that comes with the rebuild kit...the scale has a white background and the graduations are in black...the paper scale is also a T-square and sized so it can fit in the float chamber and register on the top of the float chamber edge to make the measurement easier and more accurate. I can send you a image of where the measurement is supposed to be on the float arm.
Aneroid insert (stuffer): It appears to me the aneroid cavity has an open slot to the float bowl chamber so it would affect the volume of gas in the float bowl...my gut feel is that the insert should be there otherwise there will be excessive sloshing of gas and hence excessive movement of the float...maybe someone else on the forum can comment on this or maybe Stewart Griffin can open his M4ME carb up and see if there is a aneroid insert in it.
Regards,
Henry
Thanks, Henry. I'll ask about the aneroid cavity insert when I call to order parts.
Henry and I have been discussing a few other small parts, and I'm wondering if anyone else can shed light on whether my carb is supposed to have them.
Retainer and seal on the top of the accelerator pump stem: These parts appear on an exploded diagram of a M4ME in the book by Doug Roe. My current pump does not have them, and when I look up the replacement pump for my carb model on quadrajetparts.com, it also does not have these parts. Also we know from some of the other parts we've discussed that the Roe's exploded diagram does not match my carb in some respects.
Small copper spring on top of the check ball: When I took the check ball retainer screw off, there was a tiny copper spring sitting on top of the check ball. This seems to be unusual for a Qjet. Is the spring supposed to be there?
Thanks, guys.
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Well the seal in my pic is metal, it works like a crush washer. That’s what comes with a quality n/s.
I have never seen a rubber one.
IDK, something the remanufacturer who did your carb used.
If either your n/s or that seal under the seat leaks it will render your float useless and overfill the bowl from the pressure of the pump.
Did you have hot start problems prior to removal of the carb.
As in having to hold the pedal to the floor to get a start after sitting say 15 minutes hot.?
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Looked around and the only rubber seal I see is when the threads are stripped and a press in type is used.
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I'll have to look at the ring again - I haven't actually pulled it out and handled it. It looks like black rubber, so I just assumed that's what it is. I'll have to double-check the threads also. The seat backed out normally and did not give me the impression that anything was stripped.
I have not had any major hot start problems since I switched to E0 gas. Occasionally in hot weather it was a little temperamental on hot re-starts, but I think that was prior to the carb being rebuilt. Before I switched to E0 gas, hot starts were quite difficult.
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I'll have to look at the ring again - I haven't actually pulled it out and handled it. It looks like black rubber, so I just assumed that's what it is. I'll have to double-check the threads also. The seat backed out normally and did not give me the impression that anything was stripped.
The ring is metal and the threads are not stripped. Sorry for the confusion.
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Retainer and seal on the top of the accelerator pump stem: These parts appear on an exploded diagram of a M4ME in the book by Doug Roe. My current pump does not have them, and when I look up the replacement pump for my carb model on quadrajetparts.com, it also does not have these parts. Also we know from some of the other parts we've discussed that the Roe's exploded diagram does not match my carb in some respects.
I wasn't looking in the right place for the retainer and seal. They are pressed into the air horn (see photo).
But I'm still wondering about the aneroid insert and check ball spring.
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I rebuilt the carb, but I'm still having some issues. I did the rebuild kit from Quadrajetparts.com, which included new needle/seat, accel pump cup, check ball, and pump stem seal. I also did the following:
New nitrophyll float
New power piston retaining ring
New fuel filter and fuel nut gasket
Re-sealed all well plugs with JB Weld Marine grade epoxy (supposed to be resistant to fuel, heat, and expansion/contraction)
Added an aneroid insert that is an exact fit for the cavity
Added the proper link between the vacuum break and the secondary air flap
Removed the spring that was in the check ball well
Ran through the various choke adjustments on the kit's instruction sheet
It appears that the bowl is still over-filling, as evidenced by a saturated air horn gasket and the top of the fuel level being visible through the rear vent.
I went through the standard lean-drop tuning procedure, which seemed to behave normally, but the exhaust still smells rich. No smoke or soot, though.
Cold starts are difficult; I have to crank for a while and pump accelerator to get it to fire. No problem with warm/hot re-starts.
The curb idle is relatively normal once it's off of high idle, but after driving for a few minutes, the curb idle speed increases on its own, such that it sounds and feels like high idle. I verified that the high idle cam is in the lowest position, and also verified that the throttle is not sticking part way open (idle speed adjustment screw is in contact with the throttle stop).
The choke and high idle appear to be working as they should. Choke snaps shut when the throttle is opened and high idle cam goes up to the high step. Choke opens a crack once the engine starts, and then gradually opens all the way over the next minute or two. High idle disengages with a light tap of the pedal.
I'm beginning to think that excessive fuel pressure is the culprit, as I am pretty sure that I got everything reassembled right and the float adjusted right. I'm considering adjusting the float downward a few 32nds below the spec, just to see if that will generate enough additional buoyant force to close the needle. Any thoughts on that?
I don't have a gauge with which to check fuel pressure. The pump looks like the standard stock GM mechanical pump, although I am fairly certain it is not the original pump. Anyone ever hear of these pumps generating too much pressure.
Thanks.
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Many aftermarket pumps put out too much pressure.
Inline gauges are relatively cheap, local parts stores should have one but you will need a section of rubber fuel line to place it in if you still have the all metal fuel line to the carb.
Any more than 7 psi can start causing problems.
You mentioned no hot restart problems which leads away from high fuel pressure though.
You have no way of knowing how the carb is calibrated unless you measure all the passages, jets, rods etc.
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Thanks, Blazer.
After much observation, I am pretty sure that I have two problems with the carb. First, the bowl is leaking, which is the cause of my cold start problems. Engine will start after it sits for up to 24 hours, but any longer than that and I have to crank 10-15 seconds to fill the bowl, then it will start normally. I measured the float level through the vent and confirmed that the float level is low (about 27/32 below top of bowl) when I am having the cold start problem. I also checked about an hour after running, and there was raw fuel on the floor of the manifold and fuel vapors rose up through the carb when I opened the throttle plate. It also acts slightly flooded when I wait about an hour before attempting a hot re-start. So I'm guessing I did something wrong when sealing the well plugs.
Second carb problem is the flooding. When it is running at idle, I can measure the float level through the vent, and it is at the fully up position (about 3/8 to 13/32). I can see fuel on top of the float, and at one point I measured the depth of the excess fuel at about 3/8" above the float, which would put the fuel level about even with the top of the bowl. I guess fuel pressure is the prime suspect at this point, but I'll have to tear the carb down again to make sure something isn't wrong with the installation of the float, needle, and seat.
I think I have discovered a third problem with the distributor, although I'm scratching my head over this one. With the vacuum advance disconnected and the hose to the carb plugged, I set the initial timing advance at 12* before TDC and the idle to about 830 - 850 rpm (it felt too rough at the factory spec of 700). When I connected the vacuum advance, the idle increased to approx. 1180 rpm, and the timing displayed 4* after TDC. The increase in rpm is to be expected when applying the vacuum advance, but the retarded timing seems completely off the wall. Searching the www, I found one thread on a corvette forum where a guy had a similar problem with vacuum advance appearing to retard the timing. The solution that was suggested is that somehow the pickup coil wires got reversed and were causing a problem with the firing order when the vacuum advance was applied. I don't know how that would happen unless it was just a manufacturer's defect in the pickup coil. Here's the thread - post #28 on page two presents the theory about the pickup coil wires: https://www.corvetteforum.com/forums/c3-tech-performance/2493663-vacuum-advance-is-retarding-my-timing.html (https://www.corvetteforum.com/forums/c3-tech-performance/2493663-vacuum-advance-is-retarding-my-timing.html)
Any thoughts on what might be going on with my distributor? I should note that when the mechanic replaced the valve train parts recently, the distributor was taken out and the cap was off. Is there anything he could have done when re-installing it that would cause this problem?
Thanks.
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Here are some pics of the distributor. Sorry for the poor quality - back of the engine compartment is a tough place to take a picture.
I traced all the spark plug wires and verified that they are all going to the right plug.
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Here are some better pics with the rotor off.
I noticed that the mechanic's helpers had not put the distributor cap back on quite right. The little tab in the back that makes it sit in exactly the right spot was not engaged properly, and one of the hold down clamps was not fastened. I put the cap back on ensuring that I got all that right, but it had no appreciable effect on the timing anomaly. It's now reading 10* before TDC without the vacuum advance and 3* after TDC with the vacuum advance hooked up.
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I think I figured out the timing anomaly, and I think it is due to timing light operator error.
It appears that the timing light's pickup is catching the spark from both the number 1 wire and the immediately adjacent number 3 wire. With the vacuum advance connected and the timing light's advance feature set to 0, the timing mark is advanced out of view when the light flashes from the number 1 wire, while the flash from the number 3 wire happens to be catching the timing mark as it passes the 3* retarded point on the scale. Increasing the timing light's advance setting to 33 brings the timing mark back to the zero point on the scale.
So it appears that the vacuum advance is adding about 23 degrees of advance at idle. So now I need to figure out if that is an appropriate amount of advance to be adding at idle.
Sorry for all my confusion.
Edit: That explanation about the spark from the #3 wire is not correct. If the light were sensing two sparks per revolution, that would throw off both the advance function and the rpm function, neither of which appear to be the case. With the vacuum advance disconnected, the initial advance reads at the 10* point on the balancer, and I can successfully use the advance function to bring the mark back to the zero point by plugging in 10* of advance. So I still don't know what's causing the 3* retarded reading with the vac advance connected and the light's advance set to 0. But my hunch is that the 33* reading I get by advancing the light until the mark goes back to zero is correct. And the rpm reading I get sounds right, but I guess I don't really know without an independent check.
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Hi guys - I've been continuing to work on my issues and have reached a point where I have another question I'd like to ask the group:
Can anyone recommend a good quality Qjet fuel filter with the check valve? I installed this filter with a valve: https://quadrajetparts.com/long-paper-carburetor-fuel-filter-with-check-valve-p-82.html (https://quadrajetparts.com/long-paper-carburetor-fuel-filter-with-check-valve-p-82.html)
It helped reduce the fuel pressure and mitigate the overfilling/flooding issue, but after a couple of weeks the valve stuck and shut off the flow of fuel completely. The one I used looks like a poor design in that the valve is a flat circular nylon disk. It doesn't stay straight as it moves back and forth in its range of travel, and thus is prone to getting stuck. A ball valve would make a whole lot more sense, but in searching online I have not been able to find a filter with a ball valve.
Stupid me thought the fuel pump had died, so I replaced the pump before it dawned on me that something might be wrong with that $2.95 filter. The replacement pump is rated at 9 PSI max, as are all of the OEM replacement pumps that I've seen (here's the one I installed, which looks identical to my old one -- https://www.napaonline.com/en/p/CFPB0205P (https://www.napaonline.com/en/p/CFPB0205P)). I think they are designed that way specifically to overcome the resistance of the fuel filter check valve, which is part of the OEM fuel delivery system. So I'm thinking I pretty much have to have the check valve filter if I'm going to run a stock fuel delivery set-up. If possible, I'd rather solve this issue with the filter than by using a non-OEM pump or re-plumbing the fuel line to put in a pressure regulator.
Thanks.
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I'm interested in any recommendations you might have for a replacement carburetor.
'78 GMC K15 chassis/drive train with an '85 C10 body
Remanned crate 350 (stock) with less than 500 miles on it, mated to an old TH350 that came from a third (unknown) donor vehicle
No emissions control equipment other than pcv hose running from driver's side valve cover into front of carb
Original stock air cleaner from the '78 truck
Carb, intake, fuel pump, and all ignition equipment re-used from the old engine
Fuel pump and fuel lines appear new
The intake appears to be the original stock intake from the '78 truck, but the carb is not. The truck should have a 4MV quadrajet with divorced hot air choke, but it currently has a 1983 E4ME model with electric choke and several currently unused emissions features. I am having some idle and driveability problems that were not solved by a re-build (details here if you're interested: http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0)). It was better for a short while after the re-build, but now is even worse than before. While it might be possible for a quadrajet expert to get it running right, I don't have such an expert available to me, so I think it's time to quit fooling with it and just replace it with a carb that is better matched to an old 350 with no emissions equipment.
From searching various auto parts websites, I see that there are remanned 4MV quadrajets available from National Reman, United, and Autoline for what appear to be reasonable prices with a 1 year warranty. It also appears that there are several Edelbrock Performer and Holley Street Avenger models that are supposed to bolt on to my manifold, although prices for these are a good bit higher than for the remanned Q-jets.
Also my mechanic suggested that I consider a Carter aftermarket replacement with a manual choke. I wouldn't mind the manual choke, but my searches did not find anything manufactured by Carter. My understanding is that Carter is no longer in business, so any Carter carbs likely would be remanned, correct?
Any thoughts about any of these potential replacements? Or any other suggestions?
Thanks.
Edit: I should explain how the truck is used. It's a short distance errand/light to medium duty hauling truck. Not exactly a DD since I don't use it to commute and probably drive it less than a thousand miles a year. Although I like the cool factor of driving an old truck that is in pretty decent shape, it is not intended to be a show truck or a performance truck. So I'm interested in a reasonably priced carb that will get me down the road with a minimum amount of fuss.
Quick fuel SL 750 vs. easy carburetor to work with very tunable. Factory adjusted to fire many scenarios (https://uploads.tapatalk-cdn.com/20180615/56b93923e98575f77c5f6830d7cc0b65.jpg)
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Stock Non-CCC quad off 83 1/2 ton:
(https://i.imgur.com/UOgRhcT.jpg)
(https://i.imgur.com/3tARniK.jpg)
(https://i.imgur.com/z6nG59C.jpg)
i can't help with where to connect the thermac----until next weekend IF we're lucky. But i don't think that is causing your driveablility problems, so it's not urgent.
Would love to have that carb...
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Why?
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Why?
Cuz i have an 83 and i would like back to original lol. I’m currently runnin a slayer750
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I'm interested in any recommendations you might have for a replacement carburetor.
'78 GMC K15 chassis/drive train with an '85 C10 body
Remanned crate 350 (stock) with less than 500 miles on it, mated to an old TH350 that came from a third (unknown) donor vehicle
No emissions control equipment other than pcv hose running from driver's side valve cover into front of carb
Original stock air cleaner from the '78 truck
Carb, intake, fuel pump, and all ignition equipment re-used from the old engine
Fuel pump and fuel lines appear new
The intake appears to be the original stock intake from the '78 truck, but the carb is not. The truck should have a 4MV quadrajet with divorced hot air choke, but it currently has a 1983 E4ME model with electric choke and several currently unused emissions features. I am having some idle and driveability problems that were not solved by a re-build (details here if you're interested: http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0)). It was better for a short while after the re-build, but now is even worse than before. While it might be possible for a quadrajet expert to get it running right, I don't have such an expert available to me, so I think it's time to quit fooling with it and just replace it with a carb that is better matched to an old 350 with no emissions equipment.
From searching various auto parts websites, I see that there are remanned 4MV quadrajets available from National Reman, United, and Autoline for what appear to be reasonable prices with a 1 year warranty. It also appears that there are several Edelbrock Performer and Holley Street Avenger models that are supposed to bolt on to my manifold, although prices for these are a good bit higher than for the remanned Q-jets.
Also my mechanic suggested that I consider a Carter aftermarket replacement with a manual choke. I wouldn't mind the manual choke, but my searches did not find anything manufactured by Carter. My understanding is that Carter is no longer in business, so any Carter carbs likely would be remanned, correct?
Any thoughts about any of these potential replacements? Or any other suggestions?
Thanks.
Edit: I should explain how the truck is used. It's a short distance errand/light to medium duty hauling truck. Not exactly a DD since I don't use it to commute and probably drive it less than a thousand miles a year. Although I like the cool factor of driving an old truck that is in pretty decent shape, it is not intended to be a show truck or a performance truck. So I'm interested in a reasonably priced carb that will get me down the road with a minimum amount of fuss.
Quick fuel SL 750 vs. easy carburetor to work with very tunable. Factory adjusted to fire many scenarios (https://uploads.tapatalk-cdn.com/20180615/56b93923e98575f77c5f6830d7cc0b65.jpg)
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Thanks for the suggestion, Roadrunner. At this point I've invested a good bit of time and energy into getting my current carb working right. Not quite there yet, but I think with a few more tweaks I can get it performing acceptably. The truck is too much of a Frankentruck to get everything working together to the OEM specs, so it'll probably involve some band-aid solutions.
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I'm interested in any recommendations you might have for a replacement carburetor.
'78 GMC K15 chassis/drive train with an '85 C10 body
Remanned crate 350 (stock) with less than 500 miles on it, mated to an old TH350 that came from a third (unknown) donor vehicle
No emissions control equipment other than pcv hose running from driver's side valve cover into front of carb
Original stock air cleaner from the '78 truck
Carb, intake, fuel pump, and all ignition equipment re-used from the old engine
Fuel pump and fuel lines appear new
The intake appears to be the original stock intake from the '78 truck, but the carb is not. The truck should have a 4MV quadrajet with divorced hot air choke, but it currently has a 1983 E4ME model with electric choke and several currently unused emissions features. I am having some idle and driveability problems that were not solved by a re-build (details here if you're interested: http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=35689.0)). It was better for a short while after the re-build, but now is even worse than before. While it might be possible for a quadrajet expert to get it running right, I don't have such an expert available to me, so I think it's time to quit fooling with it and just replace it with a carb that is better matched to an old 350 with no emissions equipment.
From searching various auto parts websites, I see that there are remanned 4MV quadrajets available from National Reman, United, and Autoline for what appear to be reasonable prices with a 1 year warranty. It also appears that there are several Edelbrock Performer and Holley Street Avenger models that are supposed to bolt on to my manifold, although prices for these are a good bit higher than for the remanned Q-jets.
Also my mechanic suggested that I consider a Carter aftermarket replacement with a manual choke. I wouldn't mind the manual choke, but my searches did not find anything manufactured by Carter. My understanding is that Carter is no longer in business, so any Carter carbs likely would be remanned, correct?
Any thoughts about any of these potential replacements? Or any other suggestions?
Thanks.
Edit: I should explain how the truck is used. It's a short distance errand/light to medium duty hauling truck. Not exactly a DD since I don't use it to commute and probably drive it less than a thousand miles a year. Although I like the cool factor of driving an old truck that is in pretty decent shape, it is not intended to be a show truck or a performance truck. So I'm interested in a reasonably priced carb that will get me down the road with a minimum amount of fuss.
Quick fuel SL 750 vs. easy carburetor to work with very tunable. Factory adjusted to fire many scenarios (https://uploads.tapatalk-cdn.com/20180615/56b93923e98575f77c5f6830d7cc0b65.jpg)
Sent from my iPhone using Tapatalk
Thanks for the suggestion, Roadrunner. At this point I've invested a good bit of time and energy into getting my current carb working right. Not quite there yet, but I think with a few more tweaks I can get it performing acceptably. The truck is too much of a Frankentruck to get everything working together to the OEM specs, so it'll probably involve some band-aid solutions.
Mine is also. Tryin to bring it back to life. Slayer 750 worked great on this mildly modified 350. I wish i had all original parts to start with, then could tweak wat i wanted. But Frankenstein says no lol
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