Chevy-SS

My car is a 2004 Coupe, stock LS1, auto trans. I bought it 18 months ago, and it has always had a VERY noticeable piston slapping type of noise while warming up. The slapping noise would still be slightly noticeable until fully warmed up to 185 degrees or so.

I had a buddy tweaking the engine settings a little, and I told him about the slapping noise. He has been working on cars for 40+ years and his family owned a Chevy dealership. He currently operates a high-performance shop where he dynoes cars, tunes, and does all kinds of other stuff. He does a lot of Vette work.

Anyway, he figures the slapping noise is mainly being caused by piston rings that are sticking. He suggested I change the oil and use the Zmax treatment (oil & gas). He swears that many of his customers have had success reducing or eliminating the slapping noise. I was very skeptical, but I changed the oil and filter, tossed in some fresh Mobil 1, and also added the Zmax to the oil & gas.

Honestly, I expected zero results, but after driving maybe 400 miles, I absolutely notice a DECREASE in the volume of the slapping noise at startup, plus the slapping noise goes away earlier in the warmup cycle. I will keep reporting on this, but I am very pleasantly surprised by the results so far. This is a cheap and easy thing to try, so if a piston slapping noise is driving you crazy, try the Zmax and oil change.

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EDIT - changed "slap" to "slapping noise"

moserbe

Keep us updated. I have this in my 2007 Trailblazer SS LS2.

SCM_Crash

Piston slap is caused by the material difference between the piston and the sleeve. There was some room added between them because they expand from heat at different rates due to the different metals they're made out of.

itzza427

I'll keep this in mind,,but mine is pretty slight,,and once the oil temp hits 180,,it's pretty much gone!! I WILL be watching for any updates!!

dklowrider

hmm. i've heard of changing oils [switching brands] having a supposedly noticeable difference in the slap, but anything i've known about it has nothing to do with sticking rings. is Zmax thin like Seafoam or thick like STP?

dougbfresh

If that "fixed" it, it wasn't piston slap to begin with. Look up the definition of Piston Slap.

damilleniumboy

uh oh, interesting thread.

dklowrider

well, he didn't exactly say it 'fixed' it.

dklowrider

just like that first black cloud you spot on the horizon, you just know a storm's coming.

SCM_Crash

Exactly. All sleeved SBC's have piston slap. It's not something that's fixable (or should be fixed) and in fact it is part of the design of the motor.

Couldn't agree more. There's going to be a lot of uneducated assumptions about piston slap coming. I can see it over the horizon now.

Mike Gallagher

My understanding is the cold size of the piston is smaller so the piston fits once up to temperature. Thus the piston slap before warm up.

Cybermind

With a 2004, I would take a guess and say that what you were hearing was probably valvetrain noise (clatter) and not piston slap. I believe that GM added a dry graphite (or teflon) coating to the piston skirts on 03 and 04's in order to alleviate the noise. I think they also tightened up the tolerances. Of course, some of them still have piston slap but it is not as common as the previous years.

Valvetrain noise makes more sense if your were able to quiet it down using an oil additive. I don't think it would have worked with piston slap. However, based on my experience it probably will be a temporary solution once the effects of the oil additive begins to wear off. Just my two cents.

Mark C5

Sticking rings

Chevy-SS

I have heard plenty of these engines with absolutely no audibly noticeable piston slap (or other noises) during cold startup. Mine, however, does make a lot of noise, so somethin' ain't quite right.



Chill out, man. Basic piston slap is simple to understand, I would bet almost every single forum member knows what causes it.



BOTTOM LINE - the guy that gave me the Zmax advice is very smart and has spent over 40 years working on high performance cars. He recently finished a 2-year stint working directly for GM. I would put him up against ANYONE on this forum for sheer volume of automotive knowledge.

I was indeed skeptical of the Zmax idea, but the noise has diminished, so perhaps my problem is actually sticking rings combined with some piston slap (or even some other problem). Draw your own conclusions.

EDIT - Just to be clear, I realize that an oil additive will NEVER fix excessive 'piston slap'.

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Chevy-SS

Yes, yes, this was my initial reaction too when the guy first suggested the theory to me.

But, what the heck, it's an inexpensive experiment and my ears tell me there is absolutely a difference. So I'm not laughing quite as hard anymore.

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Dave68

I reduced the "slapping" noise by simply switching to a better-flowing oil filter (K&N). The noise is not gone completely, but it is certainly diminished.

Tech

I installed a camshaft, longtubes and Corsa. The sound from the piston slap diminished.

AUandAG

I credited the noise elimination/reduction of slap to a change from Mobil 1 to Pennzoil Platinum. You've made me realize that it may have been the switch to a Wix filter.

oneshot

I too switched to a WIX filter but I still use Mobil 1 oil and the piston slapping noise or valve train chanter is almost gone.

Louder exhaust and louder stereo will not hurt either.

Dave68

Switching from a 10W-30 to a 5W or 0W-30 or 40 weight oil will also improve flow, even at 70 degrees F. Since I never changed the oil or viscosity, I attributed the reduction in slap noise to the filter swap.