GM Engine "Piston Slap" Defect

[Russ T.]

Anyone who has experienced this phenomenon in their new Corvette may be interested in reading up on it at the following web site: www.pistonslap.com.
My nephew's new Pontiac G6 is doing the same thing and it appears to be a common malady. It's a real educational site and may be some helpful ammunition after your dealer tells you that it's a "normal" noise (sounds like a diesel engine when you start it cold).

[Rob Dame]

Re: GM Engine "Piston Slap" Defect

My 02 Suburban 6.0 has the slap. The dealer told me is was normal. I called the 800 # in the back of the owners manual and bitched. I told them I had a 50 year old Chevy with solid lifters in the garage that didn't sound this bad. I argued that if it was not a problem they wouldn't mind putting their money where their mouth was or fix it. GM gave me a 100,000 drive line warranty for $0.

[Don 42616]

Re: GM Engine "Piston Slap" Defect

Is it any wonder that GM is losing market share? Interesting WWW site. The piston slap sounds like my now infamous 1978 Olds diesel that had to be towed every other day. I had to almost give it away at 5000K miles. At the same time a GM CEO was interviewed why they replaced a metal transmission part with PLASTIC his answer was GM saves $5 per car. I did not buy another new GM product until my 2002 corvette & it has had 2 computers, 2 headlight motors, gas sender gauge go out. My wife has a 1991 Lexus that still runs like new.

Our old vettes were the last of the best.

Saying this piston slap is NORMAL shows how GM views its customers. They have not really changed. Don

[Gary R.]

Re: GM Engine "Piston Slap" Defect

Interesting reading. There is a gentleman here in CT that runs an automotive machine shop,Kehl Tech. I paid him to bore a 350 block .030 over and he felt going .035 was better because "corvettes run hot" The same situation would apply here the pistons would have slapped then failed in use in short order. Ring gaps were .034" with new rings in each bore.

[Duke W.]

Re: GM Engine "Piston Slap" Defect

Piston slap is part the the vintage SHP engine cacophony that many of us know and love, but there's a limit. A guy I know once fit the OE 327 forged pistons at .0065" clearance (his "performance engine rebuild shop" recommended this clearance) rather than the GM recommended .0028-.0035"and they banged around so much a skirt broke within a few thousand miles.

I looked at the photos and could barely call the cylinder wall scored and could see no wear at all on the polymer coated skirts. What am I missing? The engine idled just like a good diesel should.

GM had some noise complaints on '01 LS6 engines, so they changed to polymer coated skirts and tightened the clearance. Supposedly the purpose of the polymer coating was to prevent cold scuffing with the tighter clearance.

Poor GM. First, there's the Dexcool flap and now piston slap flap. It's almost poetic.

Duke

[Peter L.]

GM Engine Piston Slap Flap-Deja Vu All Over Again

My 1955 Chevy 265 V8 had piston slap because the pistons broke. I was young and cheap so I fixed the one piston and then another one developed a slap because it broke. Being somewhat smarter on the second one, I replaced them all with non-GM pistons which set me back a bit but it solved the problem. Sounds like the 1965 and up Corvette disc brake caliper problem, which was solved by sleeving by folks other than GM as far as I know. Poor GM hell; poor us. Pete

[Randy G.]

Re: GM Engine "Piston Slap" Defect

Because our 2002 Corvette Convertable has the same noise, I ALWAYS have the dealer change the oil whenevery it's due so there is no discussion about oil brands and intervals if we have a problem. At the same time, I made sure the service writer noted in the paperwork and in their computer that from day one we have a noise so annoying that makes the kid behind the window at a drive through think we have no oil in the crankcase.

When the warranty was coming up, the service manager at the dealer told me to call GM and do what you did...complain. I told GM if they were so confident that the noise wasn't a problem, then they should assume that risk, not me. I got a free 100,000 mile complete drivetrain warranty out of the deal.