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2.8 valve adjustment woes.

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Old 08-23-2007, 10:16 PM   #1
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2.8 valve adjustment woes.

So I havent been on here in a while but I have some questions. I pulled the valve covers and did a valve adjustment on the 2.8 and after installing a new return fuel line in the process I am trying to get it back on the road. Everything went as planned however... The truck did not want to start at first and when it did it ran funny. (sounded diffrent) After the warm up high idle settled, the idle dropped way below what it should be stock. The truck sounds like it has a nasty stall out cam in it. It is very cool and all but is not the way it is supposed to be and wont get out of its own way during a short test drive. After running like crap I filled the tank with fresh gas (it sat for a while) and put sta-bil and fuel injector cleaner in it. It runs better but still not the same. the battery cables were off for about 2 months. Is there a learning process the engine must do. Or something I must do to help it. Or any ideas on something a messed up. I am confident in my work but have retraced my steps several times and cant find the problem. help please.

Also if you read this far I dont think you need an apology for a long post. thanks in advance.

P.S. It's tbi and a 5-speed 93' s-10

Last edited by cams; 08-23-2007 at 10:17 PM.
Old 08-24-2007, 10:26 AM   #2
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Re: 2.8 valve adjustment woes.

are you sure you adjusted the valves right? after there is no lash, the common census around here is 3/4 of a full turn past. yeah the tbi does have a learning process
Old 08-24-2007, 12:06 PM   #3
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Re: 2.8 valve adjustment woes.

are you sure u didnt acadently disconnect a vacum line thats what my truck did when i hada vacum line leak
Old 08-24-2007, 03:25 PM   #4
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Re: 2.8 valve adjustment woes.

Your lucky we read that far into your post. You should give us cookies!

Are you sure you adjusted the right valves on the correct TDC for them? And it is a 1 1/2 turns after lash if removed on 2.8's.
The computer may also need to relearn. Its like a crap shoot with that. I have seen some that need it and others that do not.
Old 08-25-2007, 02:48 AM   #5
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Re: 2.8 valve adjustment woes.

As I said before I am confident in my work, and believe I did everything right. I am a marine mechanic but specialize in outboards and hard parts. I have done many valve adjustments before but have never worked on a 2.8 before. The adjustment is right, manual says 3/4 after lash is taken out. I also did a comp. test to back it up and it all checks out. I just want to know if there is a secret I am missing (learning process) thanks for the info guys, i'll keep working at it.
Old 08-25-2007, 11:56 AM   #6
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Wink Re: 2.8 valve adjustment woes.

Quote: Originally Posted by cams
As I said before I am confident in my work, and believe I did everything right. I am a marine mechanic but specialize in outboards and hard parts. I have done many valve adjustments before but have never worked on a 2.8 before. The adjustment is right, manual says 3/4 after lash is taken out. I also did a comp. test to back it up and it all checks out. I just want to know if there is a secret I am missing (learning process) thanks for the info guys, i'll keep working at it.

I've got a few years experience on Cat diesel truck engines, and small block chevys, but not alot with the 2.8s. Maybe I can help you out though. Every chevy I've ever adjusted valves on (not running) came out just "ok" at best. it seems like it's hard to get a good adjustment on the lifters without the engine running.. (at least on SB chevys) When I to an engine build, I adjust the valves on the engine stand to get them close, then when I get the engine running and warmed up, I pull off one valve cover at a time and adjust each valve individually... this way you're SURE you've got the exact amount of lifter preload... if the reccomended preload value for the 2.8 is 3/4 turn, than that's what I'd stick with. 1 1/2 turns sounds like ALOT. the last think you want to do is have you lifters with to much pre-load and wipe out your camshaft lobe(s).

Get your engine up to operating temp. remove valve cover. with engine idling, back off a lifter adjusting nut until you just start to hear an audable tick, tick, tick, then VERY VERY slowly turn the nut back down till the tick is gone. you are now at zero valve lash. now give it your 3/4 lifter pre-load. remember... VERY slowly. if you run the nuts down to quick, you'll for sure bend a pushrod and and probably kill the engine at the same time.

Do this proceedure for every lifter. yes, it'll be messy, but it's well worth it. and with a little practice you'll get to where you'll be able to do one bank of cylinders in under 5 min.

I have done more than 20 chevys this way and it works every time.

Good luck!
Old 08-25-2007, 06:27 PM   #7
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Re: 2.8 valve adjustment woes.

Quote: Originally Posted by cams
As I said before I am confident in my work, and believe I did everything right. I am a marine mechanic but specialize in outboards and hard parts. I have done many valve adjustments before but have never worked on a 2.8 before. The adjustment is right, manual says 3/4 after lash is taken out. I also did a comp. test to back it up and it all checks out. I just want to know if there is a secret I am missing (learning process) thanks for the info guys, i'll keep working at it.
If you are confident in your work why are you having a problem and in here posting a question about it? That is not showing confidence. My manual, a true Chiltons, not a haynes or a chilton published by haynes says 1 1/2 turn. 3/4 turn on a fine threaded stud does not put much preload on a lifters plunger.

Last edited by MadMikeZ28; 08-25-2007 at 06:29 PM.
Old 04-21-2011, 08:09 PM   #8
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Re: 2.8 valve adjustment woes.

This thread is almost 4 years old. Can I hijack this thread? I have a similar problem to the original post.

You guys have already been a big help for me before (refer to this thread, post #19). It also goes without saying that your information is just as invaluable as it is appreciated.

It all started a few weeks ago when I spun a bearing. Refer to this, post #23, for details. My sig will give current vehicle details. I replaced the bottom end with a crankshaft and bearings from an '85 Blazer 2.8. I never cracked open the top end of the engine. I also used and primed the oil pump with a drill before dropping the distributor. New oil, new filter. I fired it up last night and have alot of valve clatter from both cylinder banks. I asked my mechanic about it. He said to pop the valve covers and look for broken springs, oil squirting out of the rocker arms, etc. I peeled the 2-4-6 valve cover off and fired it up. I still have oil pressure of 40lbs at cold idle, but only a trickle of oil seeping out cylinder 4 exhaust rocker. I think it is only fair to ass-u-me popping the 1-3-5 valve cover will yield the same results so I left the other side of the engine alone for now. I asked my mechanic about the lack of oil in the top end. He suggested two possible scenarios: shrapnel from the grenaded rod bearing stuck in the oil passage feeding the top end or a misaligned main bearing starving oil flow.

Are there any opinions as to the plausibility of these scenarios? Any body else have any ideas?

Thanks again guys,

Alan
Old 04-22-2011, 10:40 AM   #9
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Re: 2.8 valve adjustment woes.

Quote: Originally Posted by crazy_driver_78
This thread is almost 4 years old. Can I hijack this thread? I have a similar problem to the original post.

You guys have already been a big help for me before (refer to this thread, post #19). It also goes without saying that your information is just as invaluable as it is appreciated.

It all started a few weeks ago when I spun a bearing. Refer to this, post #23, for details. My sig will give current vehicle details. I replaced the bottom end with a crankshaft and bearings from an '85 Blazer 2.8. I never cracked open the top end of the engine. I also used and primed the oil pump with a drill before dropping the distributor. New oil, new filter. I fired it up last night and have alot of valve clatter from both cylinder banks. I asked my mechanic about it. He said to pop the valve covers and look for broken springs, oil squirting out of the rocker arms, etc. I peeled the 2-4-6 valve cover off and fired it up. I still have oil pressure of 40lbs at cold idle, but only a trickle of oil seeping out cylinder 4 exhaust rocker. I think it is only fair to ass-u-me popping the 1-3-5 valve cover will yield the same results so I left the other side of the engine alone for now. I asked my mechanic about the lack of oil in the top end. He suggested two possible scenarios: shrapnel from the grenaded rod bearing stuck in the oil passage feeding the top end or a misaligned main bearing starving oil flow.

Are there any opinions as to the plausibility of these scenarios? Any body else have any ideas?

Thanks again guys,

Alan
Yeah, you might have shrapnel floating around. Pull your oil stick and see if it has any metalic chips. I would also suggest that you change the oil again with the filter. Cut the filter open and see if it has metal in it. You may get lucky and the lower end will hang on, but extra metal in an enigne is not too good...
Since you have already run the engine, you may be at the point of no return. After you change the oil and filter, run it again and let it warm up. You may get lucky and the clatter will clear up. One other point, the oil pressure will drop once the engine is warm. If it survives, you may want to instll a new high volume oil pump. And Mr. Lucas may help you also...
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