C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Low compression???

Old Apr 17, 2006 | 11:48 AM
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Default Low compression???

I just finished puting the engine back together for THE SECOND time.

The first time there was a coolant leak, I changed out the intake manifold gaskets and used the tightening sequence in the Helms instead of the Haynes and no more coolant problems....great

But now The engine just sounds like crap!!! and when I press the gas peddle I have to push it further than normal to get it to move. Most of the sound is coming from the passenger side of the engine.

Im really at a loss of ideas, does anybody have any clue as to what this may be????

Would bad timing do this??? Or and improperly tightened head???
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Old Apr 17, 2006 | 11:52 AM
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Hopefully you torqued the heads in the proper sequence and to specs., yes timing should be checked, also have you checked for vacumn leaks?
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Old Apr 17, 2006 | 11:53 AM
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Also, make sure the valves are adjusted properly.
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Old Apr 17, 2006 | 12:35 PM
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Originally Posted by STL94LT1
Also, make sure the valves are adjusted properly.
What valves are you refering to?
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Old Apr 17, 2006 | 12:44 PM
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Putting the engine back together.....

Are you referring to the entire engine or did you just replace the intake manifold gaskets? If it was just the intake I would bet money on a vacuum leak.
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Old Apr 17, 2006 | 12:46 PM
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Originally Posted by cuisinartvette
Putting the engine back together.....

Are you referring to the entire engine or did you just replace the intake manifold gaskets? If it was just the intake I would bet money on a vacuum leak.
The first time I took it down to the head gaskets, the second time I tool it to the intake manifold gaskets.

WHat do you mean by vacuum leak the entire intake is not sealed?
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Old Apr 17, 2006 | 12:49 PM
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He's referring to your valve train, intake and exhaust valve lash setting.
If you removed your heads-and reinstalled them-then you need to check and set the valve lash.
Best thing for you to do is go read 87 rag post, about 90-95 responses. His turned out to be a vacumn leak.

Last edited by rick lambert; Apr 17, 2006 at 12:52 PM.
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Old Apr 17, 2006 | 12:51 PM
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A vacuum leak could occur in the runner gasket area, or if the base intake gaskets shifted while being assembled. What kind of noise are you hearing from the pass. side?
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Old Apr 17, 2006 | 01:11 PM
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Originally Posted by cuisinartvette
A vacuum leak could occur in the runner gasket area, or if the base intake gaskets shifted while being assembled. What kind of noise are you hearing from the pass. side?
Its kind of a repetitive dull knocking noise. I thought it was the belt but that was running fine. The engine also rocks side to side more than it used to. You can see the engine goning side to side then the car starts to go side to side.




Note: There was absolutely nothing wrong with the engine (mechanically) before I took it apart the first time. The reason I took it apart was to replace the gaskets due to some serious oil leaking. But there were no knocking or rocking, it sounded and ran good. Im starting to wish I left the oil leak.
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Old Apr 17, 2006 | 01:16 PM
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When you put it back together the first time did you reset the valve lash? if no, you need to. You may be hearing a lifter-do to valve lash, and it will make the car run extremely crappy if not set right.
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