Do You Have Piston Slap?

**A~NICE~CAR~IS~A~NICE~CAR** · 11-13-2006, 11:41 PM

I have been coming across the term piston slap alot latley, so instead of just reading it over and not knowing what it was i looked it up and came across www.pistonslap.com.
i read from some members on LS1Tech that all or most LS1 engines have a sort of normal sewing machine sound due to the valve train? but i noticed it might sound alot like piston slap? what do you guys think?

**2002Z** · 11-14-2006, 05:05 PM

PISTON SLAP usually goes away after the motor is sufficiently warmed...at least it does on mine....does not affect my performance....i just make sure i let my motor warm up good before i put the hammer down

**sunsetorangess** · 11-14-2006, 07:01 PM

the sound is normal due too the motor being alum. and it needs too heat up for everything too get tight. There built somewhat "loose".
J

**SeVeReDiStOrTiOn** · 11-14-2006, 10:31 PM

I have a little...mine goes away when the motor is around 150*

**astyles** · 11-14-2006, 10:53 PM

mine sounds like a peterbuilt till it warms up j/k

**stimpster** · 11-15-2006, 04:27 AM

I had the problem with my 2.4 litre 1995 Beretta. The tech said it was normal and I made him fix it. I probably have the work order still. Afterwards it was fine. I think they replaced 2 pistons.

**SPECOPS94** · 11-15-2006, 04:29 AM

Concur. It is normal to hear the noise upon start up and until the engine is warm. It is not a sound that you would want to hear after the engine is at temperature! I was concerned about the same sound, having always owned carb cars until about three years ago...

Mike

**Lone Lobo** · 11-15-2006, 04:40 AM

Odd. In my '98 Z28, I don't hear any piston slap

**SPECOPS94** · 11-15-2006, 06:21 AM

Not necessarily piston slap. More like a tick from the vavle train. It is easily noticeable if you've been around Carb engines for a long time. However, I don't know about the 98s. Might be the newer design of the LS1s in later years.
Mike

**02z28ls1** · 11-15-2006, 04:31 PM

I don't buy into what lawyers have to say about mechanical things. I graduated from a technical school 25 + years ago and we discussed piston slap back then. It was well understood then as it is now. Piston slap has never been shown to result in any kind of problems with an engine. Piston slap is the result of shorter piston skirts, the design of which is to reduce rotating mass for higher rpm cabability and faster rev up. Back in the day manufacturers would make their pistons long skirted and heavy to quelch any possibilty of slap to keep grandma happy. Hotrodders would laugh at these pistons and immediately toss them in the nearest garbage can. Hotrodders were more than happy to put up with a little noise when cold as the mark of performance, like the sound of solid tappets or timing gear whine. I believe that manufacturers have had to lighten rotating mass in all their engine designs as consumer demand for higher performance and gas mileage have certainly increased over the years-not to mention the federally mandated gas mileage averages have been screwed upwards. Also the weight of the vehicles has been reduced by such means as lightening the engine block. A thinner block will transmit more noise. While lawyers will think it's a conspiracy, it's just the facts of mechanical creations. Lawyers and non-professional mechanics will not understand it, even some "professional" mechanics won't understand it, unless you've built and studied engines for a living as I have. I'm not the least bit worried about the piston slap in my engine for these reasons and more. To the lawyers I say

!!!

**SPECOPS94** · 11-16-2006, 04:37 AM

I am not referring to the skirt of a piston "slapping" the cylinder walls. That, unless I have completely missed the pont of the initial question, is why I said "Not necessarily piston slap. More like a tick from the vavle train." and applied "Piston Slap" as defined within the context of this post....

That being said, it makes sense that the noise would be more prevalent in the LS1 since it is aluminum and it obviously propagates noise more easily, and dosn't absorb it in the same manner, than a steel block might. This is the "noise" that we initially hear when we start them up.

However, the "piston slap" I refer to is not this vavle train sound heard in the LS1, but the sound heard due to vavle train problems in the older carb engines (I say ‘carb engines’ because that is mostly what I have worked on and owned over the past 30 years).

This was not a "normal" sound and if that deep tick (slap) was heard, not like the noise of a sticking lifter, cam or rod bearing, or a loose rocker arm, but being a result of a problem within the valve train, then the outcome could, and normally did, wind up being a piston reaching full compression (closest point to the cylinder head/valve seats) and coming into contact with the valve which was not fully seated.

This generally would, if not corrected, end up breaking one of the valves corresponding to that cylinder, which the piston would then beat into the cylinder head and damage it, punch a hole in the piston, and/or destroy the cylinder wall/block.

Again, I am not referring to a piston skirt "slapping" the cylinder wall. That is why I began with "Piston Slap" should be defined within the context of this post....

However, I speak only from the experience of having it happened to me and I have only formal training in engine mechanics/building and a few years of of drag racing. Thank you 02z28ls1 for your post. I am NOT being facetious!! I do appreciate your comments and found them to be refreshing and infromative.
Mike