73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 76LongBox on July 07, 2014, 11:18:54 am
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It's been a while since I've been active on the forum, but I finally am getting around to doing a little work on my 1976 GMC. Late last summer, I changed out the original engine/tranny with a GM 350 Crate Engine and a TCI StreetRodder TH350 transmission. I also went with a new Edelbrock 2101 Intake and 1406 carb, new MSD distributor, new plug wires, etc. I stayed with a mechanical fuel pump, but it is new as well. I also run non-ethanol fuel in it. The truck had factory air, but was converted to R134a a few years ago. We were able to leave that system sealed when we did the engine swap, and the A/C still works just fine.
After getting everything swapped out last year, I had some timing issues, but I believe those are now resolved for the most part. However, I still have a couple of issues with the truck being hard to start up after it has warmed up to normal operating temperature.
It will start up fine if you kill it, and then just bump the key...but if you wait a few minutes - like going into a store and coming back out to the parking lot - it is very hard to start. I have to crank on it for a little while to get it going. Also, it seems like the battery is going to give up just anytime when it's hot like that (but not when it's cold). I did put a new starter on with a heat shield when I did the engine swap, but have no idea why it struggles so much to turn it over when it's hot, nor why it takes so much to crank it hot. When it's cold it cranks up beautifully - especially if it's only been a day or two since it's been run. Just set the choke by pressing the accelerator to the floor, and it'll generally start up faster than my 2010 Silverado. It generally runs fine and idles great, even with the A/C running. It does, on occasion, bog down when accelerating heavily from a dead stop, but it doesn't do this all the time - which is also puzzling to me.
I'm not sure if I still have some timing issues, or fuel delivery, or what the problem(s) might be. If anyone can offer any suggestions, it would be greatly appreciated.
If you need any more details about the engine/tranny, let me know.
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Try this when in that situation. Push the pedal to the floor and hold for two seconds, then lift off; repeat four times in total. Then hit the starter. Report back.
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Got a couple of errands to run this afternoon, so I will give it a try and report back.
Thanks...
Mike W.
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Tried pressing the accelerator down 4 times as suggested, and it didn't change anything. Still very difficult to start, and again it seemed like it was straining to turn over the engine more than when it's cold.
Also, when it does this, it usually runs really badly for a couple of minutes after it finally cranks up. Once I get rolling, it's fine, but it idles very rough usually after the hard start.
Any help will be greatly appreciated.
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Put an insulator between the 1406 and the 2101. Edelbrocks are temperature sensitive, and the carb is normally cooled by the air flow and evaporative cooling due to the carburetion process. When you park the truck, the heat in the engine will heat up the carb, and it will be cranky until you get air flow and evaporative cooling under way again, or until the engine and carb cool down.
My original thought was that the Edelbrock was slow getting gas flow started without the choke, and that's why I had you prime the manifold using the accelerator pump. If that isn't it, it could be the heating of the carb once you turn the engine off.
For a dual-plane manifold, you want the one with the center divider.
http://www.summitracing.com/parts/edl-9266
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Thanks Rich. I will give that a try.
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What exactly do you mean by difficult to start? Is the starter cranking the motor the same RPM hot and cold, but when it's hot, the motor doesn't actually start running? Or do you mean when it's hot, the starter is turning the motor much slower than normal?
If it's turning over slowly when it's hot, try taking some jumper cables and jumping ONLY the negative battery terminal to a different ground location. Try a different ground location on both the frame and the motor. It could just be a poor ground.
Also, make sure your battery terminals are clean and free of corrosion, and the battery cables are properly tightened.
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And the cables could be bad. After ten years, they start rotting internally. No outward evidence. Can be temp dependent. If they are more than ten years old, replace them.
Still, if it is cranking, it should wick off no problem.
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Thanks for the replies guys.....
There are 2 problems when it's hot:
1. It turns over very slowly, like the battery is almost dead. It does not do this cold.
2. It has to turn over a bunch to crank when it's hot.
I hope I have #2 fixed now. I was able to pick up one of the Edelbrock 9266 spacers that Rich recommended at my local O'Reilly today and installed it this afternoon. I drove the truck this evening and went to dinner. It cranked much better afterwards, but to be truthful, this wasn't the best test as we were in the restaurant long enough to let it cool down more than when I've noticed the problem. I'll give this some more testing hopefully tomorrow.
Once I confirm that problem is fixed, I'll need to figure out the other one. I don't know if the cables have ever been changed or not. I've had the truck for over 10 years and I know I have never changed them, but never had this problem until after the engine swap either. I did paint the all of the old brackets that I reused during the engine swap, including the alternator bracket, where I believe the ground wire is hooked up...so maybe it's just not getting good contact when it's hot??
Either way, I'll do some troubleshooting around that piece in the next day or two.
I really appreciate the guidance. I'll report back as solutions are found (or not). :)
Thanks,
Mike W.
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have you tried retarding the timing for this problem?
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What's the base timing set at, and which distributor do you have? That is, how much vac and centrifugal advance do you have?
The ground spot on the alternator bracket is an issue. You need to make sure you have good ground there. The other thing is that the cables could have been deteriorating, but didn't cause a problem until disturbed. We have had, on the couple forums I frequent, a half a dozen bad sets of cables so far this year. They're cheap, so replace them.
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Thanks again guys for the additional comments. I think I'll go ahead and replace the battery cables (and the rusted out battery tray while I'm at it). I'll make sure the ground gets a good connection too.
As for the timing, I really don't know what it's set to right now. I had a mechanic take care of that for me, as that is a little outside of my realm of expertise. :)
The distributor I have is this one: http://www.jegs.com/i/MSD+Ignition/121/8362/10002/-1 (http://www.jegs.com/i/MSD+Ignition/121/8362/10002/-1)
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(http://cdn.gifbay.com/2014/03/donkey_does_this_water_flying_thing-122610.gif)
got your attention yet? get a timing light and check your timing its easy and we're here to help you out 8)
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I actually do have a timing light that I bought last year, but just haven't learned how to use it yet. :)
I'll probably try to do that tomorrow if time allows...it's one of the digital ones by INNOVA - Equus Model 5568. I think it's supposed to be a good one, and it should be easy enough to figure out, and I'll report back the timing.
BTW, I did drive the truck a bit this evening, and the warm/hot starts were MUCH better with that insulator gasket in place. The little bit that it did have to turn over to crank was pretty sluggish, but I do have new cables (and a new battery bracket) on the way.
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dont get me wrong im not saying its not your cables. but if it was something simple as timing you could solve the problem for free plus you leaned something just encase you have a emergency with the distributor next time or you can teach someone else. but cmon did you like the flying donkey? makes me laugh each time i see it
Locate the mark on the harmonic balancer and the zero mark on the timing pointer first. Disconnect and plug the vacuum advance. With the engine warmed up set the timing by loosening the distributor hold down clamp and rotating the distributor to acheive 10-12° btdc for your initial setting.
its simple
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The flying donkey is pretty funny.... :)
I've seen the timing checked before, just never done it myself, and I really didn't know what it SHOULD be set to (so thanks for that info). I should have some time tomorrow to get it figured out.
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That distributor has a tuneable vacuum advance. It could be as high as 20 degrees of vacuum advance right out of the box. So you might want to read what your timing is at idle with the vacuum advance connected first, then read it disconnected. The difference will tell you what your vacuum advance adjustment currently is. You want to be about 25* BTDC with the vacuum connected, so 10-12* base timing (vacuum disconnected) could be too much.
What you want your vacuum advance set to is a whole 'nother issue! I would set it at 8 degrees of vacuum advance, and 17 degrees base timing, which with a stock 350 and regular pump gas should be a couple degrees short of predetonation while giving you the max advance with the throttle open, which is what you want.
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rich isnt that for the manifold vacuum? i know you always preach that over ported (and i agree) but dont recall you saying it
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Yep, vac advance should be connected to manifold vacuum, as it was exclusively in cars from its introduction by Studebaker in 1930 right through 1967. In 1968, they moved vac advance to ported vacuum, a.k.a. timed vacuum, to increase exhaust manifold temperatures at idle to work with A.I.R. pumps. This was to reduce smog at idle in LA traffic jams.
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Can you educate me more on the timed/ported vacuum vs. manifold vacuum? Right now, I have the vacuum advance run to the timed port on the carb - this is per the instruction video from Edelbrock as well as the MSD documentation.
What are the advantages/disadvantages for running the vacuum advance on full manifold vacuum rather than the ported/timed vacuum?
I have no problem changing it if that's what I need to make the thing run right, but I'd just like more info. :)
I really appreciate you guys taking the time to help folks like me!!
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Read this:
http://www.corvetteactioncenter.com/forums/c3-technical-performance/60830-ported-vs-manifold-source-vacuum-advance.html
Note Edlebrock diagram below. Do you have an A.I.R. pump on your engine? If not, use manifold vacuum.
(http://www.jalopyjournal.com/forum/attachments/carb-jpg.1767695/)
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Wow Rich....what great information. I will definitely be changing over to manifold vacuum for the advance.
I currently have the vacuum manifold port on the front of the carb hooked up to some large canister that is beside the radiator on the driver's side. From that canister, a rubber hose runs to a hard line that goes across the truck under the fan shroud, and it looks like it turns back down the inside of the frame and runs toward the back - maybe to the gas tank...??? (I can't really get under the truck right now to trace it fully.) Maybe this shouldn't be hooked up this way at all? Please advise if you can....
The rear manifold port is running to my brake booster.
I do have a threaded port (currently plugged) in the manifold that is easily accessible as well. It's up front beside the water inlet/thermostat.
And regardless of which port I need to use for the vacuum advance connection, I assume I would just need a rubber cap for the timed port on the carb, right?
Thanks again for such great info.
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You can probably just swap the two lines. The fuel vent will be fine on timed vacuum.
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Thanks Rich....I'll give it all a try and report back. Might be a day or two...and again, THANK YOU for the help!!
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Ok guys....here goes....
I checked the timing (that really was easy), and without the vacuum advance hooked up (unhooked and plugged the line and the port on the carb), and initial timing was set at 4*. So, I went ahead and bumped up the initial timing to 12* and locked the distributor back down. Not fully understanding how all of this works, I went ahead and hooked up the vacuum advance to the ported/timed side of the carb (as it was before), checked the initial setting and it made no difference.
So, then I swapped the vacuum hoses as suggested above, and rechecked the timing with it hooked up to manifold vacuum. BIG difference. Initial timing now reads 30*, which if I read the info above correctly means that I have about 18* of vacuum advance.
While my distributor is "adjustable", it's apparently not as simple as it used to be on this model - now instead of using a 3/32" Allen wrench through the port, you have to take the distributor apart and put some "stop" in there turned a certain way to get it set to what you want. :(
That said, I'm not necessarily afraid to do that, but before I do (since it seems like a pain), I would like to know if that's really what I should do at this point.
Advice is MUCH appreciated.
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Yup, your disti right now is set at 18 degrees of advance. And with the centrifugal advance all in, right now at cruise you will be running 51 degrees of total advance, which is a touch high for my taste.
You can either 1) set the base timing at 7 degrees, so you get 25 degrees of advance with the vac all in and 46 degrees of advance with everything in, or 2) adjust the vacuum advance to a lower level (like 8 degrees) and set the base timing at 17 degrees, so you once again get 25 degrees of advance with the vac all in and 46 degrees with everything in.
I would prefer the 17 degrees of base timing -- performance will be better pulling out of the hole. So why do they make distributors with so much advance? Because if you are running high-compression heads, pre-ignition (detonation, or knocking) will be a problem, so the higher vac advance allows you to go to a lower base timing and avoid pre-ignition when pulling out of the hole, and still get to target advance at cruise. With the stock heads of that crate engine giving you about 8:1 compression, pre-ignition won't be a problem, even on 87 octane.
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Awesome Rich...thanks! I'll get that little "stop" installed and see what I can get it to do. Hole shots have been pretty bad with it, so maybe this will fix that. :)
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Ok....so I installed the stop at tab "C", which was supposed to be from 8-11*, and it resulted in 10*. So, I set the timing to 15* + the 10* vacuum to result in 25* initial with the manifold vacuum hooked up. I went for a test run, and it definitely has WAY better throttle response from a dead stop - no question - throttle response was better all the way through, but especially noticeable from a stop.
However, the other issue I was having with the labored turn over when it's hot is now worse. It didn't take many of the slow revolutions to get it started after sitting for a few minutes, but the revolutions were very labored. I do have the new battery cables on the way, but wondering if that was to be expected by advancing the timing so much. I guess ultimately I went from 4* to 25* initial timing, which I would think is a fairly significant swing, and with my limited knowledge, I wasn't sure what to expect for this part.
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15+10 is perfect. That'll also leave you a little more headroom against pre-ignition if you get a load of cheap, off-spec gas.
The advance makes no difference on cranking effort, except it should catch easier with the higher advance.
The throttle response is from more advance and having the vac advance on the correct vacuum port.
The cables or the starter are dying. Hopefully it's the cables.
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Once again, thanks Rich. I put a new starter on when I did the engine/transmission swap around a year ago give or take a few days, so hopefully it's not it. I have heard of people having trouble with them when they get too hot, but I did install one of the Mr. Gasket heat shields on it to protect it from the exhaust manifold.
Anyway, when the cables come in (hopefully early next week) I'll try to get them changed out and see if that helps.
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The PO of my truck put a gear-reduction starter on it, and I don't have any problems with the headers, with no heat shield at all. It really spins it up.
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If it does turn out to be the starter, I may look at that as an option. I decided when I did the swap to stick with factory style exhaust manifolds, and they are definitely very close to the starter, but I figured it should hold up ok since that's the way it was before.
It's amazing how much I have learned throughout this process, but it's also amazing how much more there is to learn. Thanks to guys like you, folks like me with a "little" knowledge, can do a lot more than we thought we could with a little help. :)
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Four years ago I was in pretty much the same position, at least with regard to the CKs. I did a lot of stuff on 60's cars back in the day as well, and it took a while for that to come back. But I don't know where I would be without forums like this one. Always more to learn.
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New battery cables and battery tray arrived today. I didn't realize how bad rusted out my old tray was...I'm surprised the battery was still sitting upright! :o
Anyway, installed the new cables, and still no joy on the hot starts. It STRUGGLES to turn the engine over - it seems to be getting worse with each passing day. So, I go to my local O'Reilly and have them test it...guy says it's not bad. I meet the wife for dinner, and while I'm eating my Arby's sammich I think back to when I first got this thing up and running with the new drivetrain last year. The starter didn't sound right from the beginning...making some odd sounds. So, the more I thought about it, the more I believed it was the starter.
So, after dinner I go to one of the other O'Reilly stores in town, and had them check the starter....they say it's bad. The voltage drops to nothing on the dash gauge when I'm trying to start the truck, so I tend to agree with this second dude that the starter is toast.
I had them look it up in their system (as that is where I bought it last year) and I bought the one that carries a lifetime replacement warranty.....so, tomorrow (if time allows), I'll pull the starter and exchange it for another one - hopefully that will solve the problem.
On a side note, while the battery cables may not have been bad, it was definitely time to change them anyway....they were the originals from 1976. :)
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Excellent move to hit the other store. Closing in on the problem, and a lot of other things tweaked up along the way.
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Was able to get the starter replaced today, and it seems (at least for now) to have solved the problem. We had a "cool front" move through last night and it's no where near as hot outside, so a quick trip down the road and back really didn't get the temp up as high as it has been getting.
Hopefully it's resolved....
I'd like to say thanks again to everyone who assisted me with the troubleshooting on this thread.
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Just thought I'd add a quick note....
I got the truck out and drove it quite a bit this evening - about 125 mile round trip (about 90 of it on the interstate @ 65-70 MPH) and the truck ran great. Starts up nicely now even when warm - there is no doubt now that the other starter had problems.
Thanks again.