73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Chisholmcody on May 15, 2015, 09:42:09 pm
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So today after work I started the truck and herd a ticking/knocking noise. I think it's the valves but I want a second opinion before I pop off the cover. Hopefully you can hear it in the video (idling high due to choke being on)https://vimeo.com/127991483 (https://vimeo.com/127991483)
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Sounds like valve chatter to me
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Kind of hard to say, it doesn't sound "heavy" as if it was coming from the lower end. How long did it last? Has it done it again? Did it sound like it was comming from the top or bottom of the engine? Does it still make noise at idle?
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Comes from the top and it's very faint at idle and yes it's still doing it.
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Ok that's good. Now try this, start the engine, let it idle, now put your ear down between the top of front tire and the wheel well opening, listen to the engine from the wheel well. If it's bottom end noise, it's going to be more noticeable here, if it is, then lay on the ground and listen under the truck, if it's even louder here, it could be in the lower end. If you do these things and it's getting quieter, it probably is from the top, in which case it's best to just pull both valve covers and take a look.
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It's louder up top. When I pull the valve cover (l6 250) what am I looking for?
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you are looking for anything that is messed up.
pull the cover and start it up and look/listen for the noise
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Good advice.
First look for broken things. Rocker arms, rocker studs, and springs. (Unlikely if it runs normally)
Second I would check pushrod to rocker arm adjustment. (More likely)
Third check for a flat lifter(s). (Again unlikely if it runs normally)
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Good advice.
First look for broken things. Rocker arms, rocker studs, and springs. (Unlikely if it runs normally)
Second I would check pushrod to rocker arm adjustment. (More likely)
Third check for a flat lifter(s). (Again unlikely if it runs normally)
This here is good. If you pull the cover off and a piece falls out then that's gonna be obvious. If you start it and most or all but 1 of your rockers moves normally except for 1 or a few that are kind of jumpy or clacking, that is probably your noise. Pictures and a look at moving parts in action is sometimes your best learning tool.
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If it is loose do I just tighten it 1/4 turn at a time? Tell noise goes away
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If it's loose, it would be best to shut the engine off, then remove the affected rockers, examine the pieces for damages and cracks, replace as needed and then reassemble properly and then of course it wouldn't hurt to check all the others. Examine the pushrods too for being worn, damaged or bent.
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A quick check for an exhaust leak would be a good idea before you go further. Do not just tighten rocker arm nuts--you have to follow the adjustment procedure. You're not likely to need valve lash adjustments unless something is damaged anyway.
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Ok I will have to take a look at it this weekend
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Today the noise got louder and louder and then all of the sudden the truck died.
So I got it towed home and the tow truck driver was talking about it and said it could be the starter . Come to find out it is not disengaging and is bad. Will be replacing it hopefully tomorrow before school.
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Well that's to bad but good news also. Keep us posted.
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I got the starter replaced it sounds better when cranking and cranks faster but ...... The motor won't start no matter what I do. I have spark but when it's cranking the fuel seems to be pushing out of the carb to intake gasket almost like it's not being sucked in. Any ideas on why?
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sounds like you may have flooded it pretty badly.
getting spark?
maybe you bumped a wire replacing the starter
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yes it does have spark. And my dad tried to start it when i was at work and it was still seeping out of the gasket/ mixture screw
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If fuel is seeping anywhere then its probably flooded or requires a rebuild. Also if fuel is flooding out of the carb chances are you will need to do an oil change.
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I did a dry compression test here's the results (average)
#1 -70 psi
#2-0 psi
#3- went from 100 to 10 psi
#4-0 psi
#5-110 psi
#6-0 psi
And there seems to be a little bit of coolant on the transmission bell housing
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Did you do the compression test with the throttle wide open? Those numbers seem extremely low.
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No throttle is closed as far as I know
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Throttle needs to be wide open to do a compression test otherwise the results are null.
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Are the numbers repeatable, cylinder-to-cylinder? Cylinder 3 changing from 100 psi to 10 psi hints at a compression gauge malfunction.
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I'll have to re test it in the morning
But I re ran a test on 1 and 2 because the high idle was on and still got the same numbers
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What do you mean the high idle was on? Did you start the engine to check compression? Does the engine start now or do you mean the throttle was held slightly open while cranking?
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No it was set so the throttle was open a little
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lol. You answered my question before I finished posting it. Recheck the compression to make sure you don't have a pressure relief valve leaking on the gauge.
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Will do 1st thing in the morning. Also picked up another valve cover gasket just incase I have to pull it off
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besides the gauge might be faulty, im not at all familiar with the I6 whats the common factor between the even cylinders vs the odd?
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https://vimeo.com/128827890 (https://vimeo.com/128827890)
Update pulled the valve cover and 2,4,6 are stuck on exhaust stroke which explains the no compression
But as seen in the video the valves are not moving. Which means it's the cam or the timing chain
Is there any easy way to tell?
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That is extremely weird. Are you sire you still have spark at all cylinders. If the valves aren't moving then either the can shaft isn't moving due to the chain being broke or the lobes are all those lobes are wiped out..highly unlikely but possible. Take the distributor cap off and turn the engine over again. If the distributor isn't rotating then its either the timing chain, can sprocket or crank sprocket. You could have shared the crank pin or on the sprocket 9r possible the bolt and pin on the can sprocket. Check the dizzy first.
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This would explain the compression results.
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I was reading online and it says the l6 250 had no timing chain is this true?
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Yes it actually has two helical cut grars... sorry for the miss info on the chain.
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Do you by chance know if those gears are plastic or are they metal
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Definitely metal gears. Which was likely the noise you initially heard
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Think they stripped?
How hard are they to replace?
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It's possible that they are worn down or even the key to one gear or the other sheared. Ease is all in the mind of the doer. If it were me I'd answer yes. All of your accessories Wil have to be removed and the balancer/crank pulley pulled. Along with the oil pan if I'm not mistaken the i6 front oil pan seal shares the timing cover just like the v8's. But the good news is this engine has been used since the 60's so finding parts are almost as easy as a 350
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Am I able to remove the oil pan with the motor still in the vehicle or should I pull it
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And are the gears pressed on or do they unbolt?
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I've never disassembled one of these but it wouldn't be hard o determine if the oil pan front rail shares a seal with the timing cover. However you may be interested to know that from the '70s up to the mid '80s the cam gear was a special hardened plastic called micarta. Most aftermarket replacement gears are aluminum but the plastics are still out there and I'd avoid them like the plague! The unfortunate part is that you will have to remove the cam to replace the gear successfully. The old on which is likely still plastic can be heated and pressed off. The new one has to be pressed on as well after heating it and it needs .001_.005 clearance between the plate and the gear for proper cam thrust clearance. Unless the front end of the truck is disassembled you may need to pull the motor to remove the gear. I do not recommend trying to do it in place because you only get one shot. Once the gear cools you either force it off and get a new one or you heat it up and pray you do not damage it on the way out.
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Hmm if I have to pull the motor I might just go get a 350
But if I do pull the motor and do the gear would another a new cam with a gear already installed be the better route due to ease (if that is the issue)
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I second the 350+ morion... but I'm a power junkie so of course I'd pick more displacement.
If you bc an find a new cam with the gear already installed then I'd certainly go that route especially if I didn't have a press. I know I sky and comp offer cams but I'm not sure if they offer stock replacements or just upgrades.
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Thanks for the help I'm going to look at it more this weekend
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Ended up doing it today
It does have the plastic cam gear and that is what broke
(http://images.tapatalk-cdn.com/15/05/28/b9dc8d0aaf97acdf54cabef92ad93f40.jpg)
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Oh that's no bueno. Sorry to see that. The plastic gear definitely wasn't a good idea.
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No not at all lol
As for pulling off the old gear do I just heat it up and pry it off or is there some sort of puller
And for installing the new one can I just hit it with a deadblow?
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No idea, never had to work on one. But based on the the picture, it appears to be installed like a crank sprocket. My guess would be a 2-jaw puller grabs the back side thru those 2 large holes, then just twist it off. Install would be with an installer tool, line up the keyway and twist it on. That's all just goin off the picture and a general idea of how GM intended it to be done.
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See page 6A-1-19, "Gear Replacement," in the 1978 Service Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/ST_330_78_1978_Chevrolet_Light_Truck_Service_Manual.pdf#page=446). The gear is pressed off and pressed on with the camshaft properly supported. Do NOT use a hammer; otherwise, you run a high risk of damaging the camshaft and gear! Better to have a shop swap the gears for you.
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Thanks!
If I go the 350 route what all do I have to upgrade?
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Oh that's no bueno. Sorry to see that. The plastic gear definitely wasn't a good idea.
Even a stock 305/350 uses a nylon cam shaft gear for the earlier trucks and only get swapped out when they get replaced due to breakage. Mine was UGLY.
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I know. Just bad idea in general.
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So I pulled the grill and radiator in hopes to have enough room to pull the cam. Looks like I might!
Also I got all of the push rods out and labeled for re installation. As for the lifters what is the best way to keep them in place for when I pull the cam? And should I pull the fuel pump?
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never seen someone remove the cam and keep the lifters in place. then again i never seen nor have i done it on a inline. take pictures if you can please
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So I pulled the grill and radiator in hopes to have enough room to pull the cam. Looks like I might!
Also I got all of the push rods out and labeled for re installation. As for the lifters what is the best way to keep them in place for when I pull the cam? And should I pull the fuel pump?
???
Chisholmcody...
Did you take the time to read the service manual linked above? The answers to all of your questions are contained therein. Here's an excerpt...
[Camshaft] Removal
1. Remove engine, following procedure on page 6A-40
of this section.
2. Remove lifters as previously outlined.
3. Remove crankcase front cover as previously
outlined.
4. Remove fuel pump.
5. Align timing gear marks then remove the two
camshaft thrust plate bolts by working through holes in
camshaft gear.
6. Remove the camshaft and gear assembly by pulling
it out through the front of the block.
NOTE: Support camshaft carefully when removing so
as not to damage the camshaft bearings.
If you have questions after reading the provided instruction manual, ...feel free to ask away.... :P
;D
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just got done reading it (should have done that first). I also talked to my dads mechanic and he was saying I can use a dowel to hole the lifters in place. Or even drop the telescoping pen magnets (http://www.oreillyauto.com/site/c/detail/PFM0/20126/N0722.oap?ck=Search_N0722_-1_3550&pt=N0722&ppt=C0374) down were the push rods went and bend the tabs were it slips on your shirt to hold it on top of the head and hold up the lifters that way? Can anyone confirm this?
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So I have gotten everything back together with out a catch except for this one push rod cover on my motor (l6 250)
Every time I have put it on the gasket seems to push out of the bottom of the cover and is causing a leak. I have been using the right stuff (rtv) to try and help hold it and it's still slipping out the bottom. Any recommendations on how to get it to stay?
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Until it cures, the silicone sealer is acting like a super lubricant, causing the gasket to shift. On the block side gaskets, try substituting Permatex High Tack (http://www.permatex.com/products-2/product-categories/gasketing/gasket-sealants/permatex-high-tack-spray-a-gasket-sealant-detail) or Super High Tack (http://www.permatex.com/products-2/product-categories/gasketing/gasket-sealants/permatex-super-high-tack-gasket-sealant-detail) for the RTV.
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With the high tack or super high tack do I put it on both sides or just on the surface of the cover?
And do I put the rtv on the other side or leave it bare or even use the high tack on that side to ?
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And do I have to wait the 3 hrs for it to cure with the the super high tack or can I start the motor befor that?
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Frankly, when applied correctly the RTV creates a better seal. High Tack is best suited for paper gaskets when you're attempting to retain a stubborn gasket in place during assembly. But, it will work for non-paper gaskets, too.
...Try this before you invest in the High Tack sealer: Apply a thin smear of RTV to both sides of clean gaskets and install the covers only finger tight - just tight enough to retain the gaskets in position and force a tiny amount of sealer out along the edges of the gaskets without actually compressing the gaskets. The idea is to get the gaskets to seat into and even out the film of sealer without actually clamping the gasket and forcing it to shift. Let the silicone set up for 2-3 hours then tighten the cover bolts to the finished torque. Carefully inspect for leaks.
If the above method doesn't provide a satisfactory seal, use High Tack on both sides of the gaskets and call it done. High Tack can be put into service within about one hour after assembly.
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Hope fully I can try this tomorrow thanks for the info!
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Finally got to test drive the truck after the fix
And this happens
I was accelerating fairly easy and all of the sudden the truck hits 40 ish mph and try's to die
This happens all the time around this speed have any ideas what it is? My thoughts are ignition.
My timing is set to 7 which is were I had it before it broke (factory is 6 but adjusted +1 for elevation)
It also has another fuel line on it (few more bends to make it look nicer) that wasn't on it before it broke
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Changed my fuel line back and got a new cap and rotor and it's still doing it
But it only does it under load and if i accelerate slowly it will die around 25-30mph if i accelerate hard it will die around 40mph
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Could the distributor be off a tooth
And could the coil be bad?
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Or is the motor vapor locking at high rpms
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Unplug the distributor vacuum advance, go for a test drive, then post what happens.
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Just did that and it's still doing it at around the same speeds
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Plug the vacuum advance back in and unplug the EGR valve then go for a test run and post the outcome.
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Plugged it off but noticed it was pulling no vaccume to the egr (unless it's on a timed vacumme) but it was still not going over 40 and dying
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Heads up guys if you install a fuel filter backwards it will cause this issue lol
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I hope you replaced it rather than just turned it around or sediment could wash into the carburetor.
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Heads up guys if you install a fuel filter backwards it will cause this issue lol
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Last time I checked, filters had the word "FLOW" with an arrow pointing in the direction of flow or the words "IN" and "OUT" on each end hahaha.
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Lol mine does not it's just a little black tube and yea it is being replaced hopefully tomorrow
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Probably should get one of better quality.