Famous GM Piston Slap
03-30-2007, 08:08 AM
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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.
03-30-2007, 08:24 AM
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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.
03-30-2007, 08:26 AM
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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.
03-30-2007, 08:44 AM
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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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03-30-2007, 10:09 AM
#8
My girl friend has a 99 TA that she bought new and it has always made noise when you started it up cold..but after it runs for 5 minutes is quiet and the car has never had any oil consumption problems..it has close to 100000 miles on it now... 
03-30-2007, 12:30 PM
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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
03-30-2007, 03:14 PM
#13
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
03-30-2007, 03:39 PM
#14
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.
03-30-2007, 05:21 PM
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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.
12-19-2007, 12:58 AM
#16
my 00 does it pretty serious... it sounds like the #4 cylinder even when warm is slappin around some pretty serious. i don't think it's ever gonna cause anything serious to go wrong.
