Famous GM Piston Slap
Famous GM Piston Slap I have the famous GM slapping/knocking noise under the hood that I think everyone has and I want to quit it down alittle how do I go about that? Should I get new heads? if so then send me in the right direction for heads. Since the Cam swap about a year ago I've noticed it more.
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Joined: Jun 2006
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From: Enid, OK
Does this go away after the engine has warmed up? iv never heard of a cast piston slapping, tolerences must be way off. Forged pistons slap but thats because they expand and contract alot more then cast units due to the higher silica content.
Originally Posted by BigDB
Does this go away after the engine has warmed up? iv never heard of a cast piston slapping, tolerences must be way off. Forged pistons slap but thats because they expand and contract alot more then cast units due to the higher silica content.
Originally Posted by JayBirdWs6
yea it goes away after awhile when it warms up. I think ever since i started doing full syn oil in the bird its been more noticable too.
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Teching In
Joined: Dec 2005
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it is nothing to worry about, the motors that have the piston slap seem to be a little quicker then the ones that dont, i have been spraying a 150hp shot on mine for 2 years and it always sounded like its going to come apart when its cold
Originally Posted by JayBirdWs6
I have the famous GM slapping/knocking noise under the hood that I think everyone has and I want to quit it down alittle how do I go about that? Should I get new heads? if so then send me in the right direction for heads. Since the Cam swap about a year ago I've noticed it more.
You'd have to rebuild the bottom end, or put some coated skirt pistons in.
kinda like these
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Joined: Dec 2004
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Pffft.
This is worth 20whp to you. Leave it be.
GM put 434g short-skirt pistons with low-tension (9#) oil-rings in this engine. You will get a bit of slap until the slug expands. The lightweight pistons and low drag are worth the price imho.
This is worth 20whp to you. Leave it be.
GM put 434g short-skirt pistons with low-tension (9#) oil-rings in this engine. You will get a bit of slap until the slug expands. The lightweight pistons and low drag are worth the price imho.
mine's got it too, was kinda worried first time I cold started the car and heard it, but then remembered a lot of threads about piston slap a while back.
My 02 never had it though.
My 02 never had it though.
