Pete2k_Z28

I'd like to punch that lawyer dead in his face.

Yes, there are SOME, and a very small percentage of motors with legit issues out there.

But for the most part, piston slap is an effect of the overall design of the engine, is and should be considered normal, and not detrimental to the motors longevity, performance, or efficiency.

To say he has .000001% of an understanding of what he's talking about, it would be generous. The only thing he sees, like most scum of the earth lawyers, is MONEY.

Piston noise in the LS1's is a combination of SEVERAL issues, none of which cause any appreciable problems.

1: Aluminum block that transmits noise.

2: Short skirt, LOW FRICTION, LIGHT WEIGHT, EFFICIENT pistons.

3: Hyperutectic casting process makes pistons hard, WEAR RESISTANT, durable, lighter as they can be made with less material, and have LITTLE THERMAL EXPANSION. The last quality is perhaps the most significant.

Lets get into geometry now. Lets say you have a 4 inch diameter piston, that is 3 inches tall. Now lets say you have a .004" cylinder wall clearance. Because of the length, the tangent of wich that piston can rotate vertically, upon the wrist pin, is very low.

For the next example, we'll leave the same 4 inch diamater piston with a .004" clearance, and shorten the skirt to 2 inches. Now rotate that piston on it's wrist pin center and you will find an appreciably higher amount of "rock" in the assembly, as the length from the center of the radius to the edge of the skirt is shorter.

For a simpler visualization, although more radical, try this. Take a roll of quaters, and drop one in. Does it go down perfectly flat? No. Now glue 3 or 4 quaters together, and try it again. Does it go down flat? Yes, but does it still have some play in it? Yes. Ok, now glue 8 quaters together, and see what happens. Goes down smooth, and with little if any perceivable play.

That is a simplified example of how a short skirt piston will behave in a large bore. The obvious soloution is to tighten piston to wall clearances. This is where it gets complicated. Remember when I said hypereutctic pistons have little thermal expansion? Ok, that is a quality of the design that allows some flexability with tight bore clearance. It also means the piston won't expand much, or fast, to take up any extra clearance. But one material still remains, and the tolerances of that material cannot be changed. OIL! You have to leave slight clearance for oil to remain on the cylinder walls to reduce friction, WEAR, heat, efficiency, etc.

So what we now have is a short skirt, low thermal expansion piston, in a cylinder, with small expansion and oil clearances, moving up and down on a connecting rod attached with a pivot point.

Next up: manufacturing tolerances. The tolerance for a "perfect" bore diameter that exactly balances the requirements of thermal expansion and oil coating is extremely tight, on the order of less than +.002 -.000. To produce such a tolerance in efficient, AFFORDABLE high speed production is nearly impossible.

So let's add up the facts here.

We have high horsepower engines, that get nearly 30mpg, produce very low emissions, rev all day long to 6,000+rpm, run well over 100,000 miles, are inexpensive to manufacture and purchase, and they make a little noise.

ARE YOU KIDDING ME? ALL THAT AND PEOPLE ARE READY TO BITE THE HAND THAT FEEDS OVER A LITTLE NOISE????

I have 56,000 VERY HARD miles on my car, and it has had some piston noise since I purchased it with 17,200 miles on it over two years ago. Since then, I have put over 100 passes on the car, likely over 50 bottles of spray on the street and track, abuse the car to unbelievable extents on a daily basis, run the motor dead *** cold in the morning on the way to work fairly regularly, and it still runs as good if not better than it did almost 40,000 miles ago, has shown normal metal on the drainplug magnet, and shows up perfectly clean bores on a borescope.

The thing that people seem to be missing is that while not all GenIII motors have piston noise, many do and VERY few of them have ever developed a problem. Likely they were extreme cases that should have been resolved. The rest are just bandwagon golddiggers, or have been mislead by this ignorant, and greedy lawyer.

So go ahead, show GM how much you all appreciate them building an affordable 350hp car that ran low 13's/high 12's stock, could be had for around $20,000, gets great gas milege, handled nice, and was extremely reliable.

It's ******* lawyers like this that just kill any prospects of manufacturers even bringing such products to market ever again. So in a few years, when there is still no Camaro, Firebird, or other affordable RWD V8 sport coupe on dealer floors, that lawyer and all of his clients can pat themselves on the back then go sit in a corner and cry that GM won't make any cool cars anymore, and wonder why.

JustAnotherSS

its disturbing to start up the car every morning and hear that ****...i have a pretty loud exhaust and from the front of the car I can't hear the exhaust at all because the piston slap is so loud.

i'm going to pay more attention and see how bad it is when the car is warm.

has anyone taken this up with the dealer with mods on the car? i'm sure the blame would be pointed straight there...but who knows

kossuth

iTrader: (12)

I totally agree but the majority of the problems lie with the truck motors.
You have to consider that the majority of the motors are in vehicles like Suburbans and such. If I buy a $40,000 Suburban with the 8.1 in it I would sure as hell not want it to sound like what some of these motors sound like. If I wanted it to clack I would have gotten a truck with a Duramax.I agree 100% on that one.

GM and everybody else has been using cast iron blocks for decades without any issue like this. Remember the aluminum LS1 motor is the minority motor with the problem. The truck engines are the big problems here which still use cast iron blocks.

And that last quality is part of why these motors have the problems they do. The damned cast iron block expands more than the piston does causing the excessive clearance. Anybody who has been through any chemistry course that has dealt with thermal expansion could tell you that excessive clearances when at operating temperature are likely. Remember no one metal expands at the same rate. I would rather have a aluminum piston expand to fill a overbored cylinder vs a overbored cylinder expanding so it is way out of spec of a Hyperutectic piston, which is what is happening. With these truck motors.
I agree with everything you said and that reenforces why the bores have to be as perfect as they have to be.
I agree about the greedy lawyer part and all. Where GM messed up is they are not taking care of it's truck market like they should. Remember that is where GM is gonna get much much more of it's money than it will ever from the f-body or the y-body. Just a fact. Most of the f-body and y-body owners would never notice the noise. If they are particular enough to worry about that they probiably have installed aftermarket catbacks and such and unless it is severe they will never notice it. I'm not trying to argue just to argue but I'm looking at it from the truck owners standpoint. Alot of these trucks get used hard and have a hard life. Yes some are grocery getters but there are also the trucks that get beat and get beat hard. I dare say even more abuse than about 95% of the Vettes or f-bodies out there that frequent the track. Again I hope this works out the best for everybody. Also FYI I am not a LS motor owner but I do own a S10 pickup that I have had good luck with. I would consider myself a GM supporter but what do you do when a problem of this nature arises???

TWISTA TA

I burn about 1 1/2 quarts of oil every 3k miles. Could this be because piston slap?

Benjamin Russick

iTrader: (1)

I'll say this again because my post seems to have dissapeared... Piston slap is an inherent problem with short-skirt pistons. I had light piston slap in my worked 5.0 Ford, one of the most durable engines ever, and it never affected performance. If you have noise at warm-up, I wouldn't be too concerned. If your noise persists, or gets louder, after the car is warmed up, you have problems. Lawsuits like this benefit NOBODY.

Keith

Just tell people that noise is because of the "forged racing pistons"

Seriously though, my 2002 4.8 does it all the time and I could care less. Ain't gonna hurt anything as far as I can see. I still get 22mpg out of it and I consider that damn impressive for a truck. No oil burning either.

Colonel

My opinion is that a some slap when cold is definitely no biggy. Even a tiny bit of slap when warm is no biggy. But VERY noticable slap when fully warm should be fixed by the dealer. I mean, if it's really that bad then your engine is not going to last as long as it should normally.

I bet that wipes out 99.9% of the people who complain of piston slap.

GainesvilleLS1

iTrader: (1)

I'm with you.

black_knight

iTrader: (1)

I agree with Colonel. If it's audible over an open cutout when the engine is warm AND it's burning oil, THEN you should be able to get a fix from the dealer. But NO settlements.

And the other 99.9% of you can quit yer b*tchin.

AK's WS6

Most don't want to sue they would just like it fixed, but when GM gives a good coustomer the cold sholder about a clacking sound coming from there motor and says it's normal, then this person goes and listens to his neighbors Dodge, Ford or even another GM vehicle with the same motor and it's quiet like it should be. Where is he to go?? GM won't fix it.......now is where the lawer part comes into play, they will stick up for the little guy. Not everyone is an expert on motors so when you tell them all this tech stuff, all they are going to say is "well my neighbors 5.3 don't do it" then you say more tech stuff ,and all he hears is bla bla bla bla bla all over again. And for those that have all this great info in short skirts, iron block, aluminun this hypertectic that WHY DON'T THEY ALL HAVE PISTON SLAP????? Because some place, some where, some plant, some friday,some monday, their tolerences were off and some people got bad blocks....OK

Tokez420

so whos gunna file with them?

CammedTA

Cam pistonslap get very loud overnite? This mouring I turned my car on and all of a sudden clap clap clap coming from under the motor, I popped up hood and was like WTF. It is way louder than my valve trian. If your standing in front of my car you can hear it of my cammed Loudmouth exhaust!!!! This is not something I going to f!#king live with either. I am pissed off!!!!!!!!!!!!!!

kossuth

iTrader: (12)

Well first off the slap is known to occur within the first 12k miles or so. If you didn't have it by then then you probiably won't develop it. Second off with your mods there is no way any dealer or even GM would warranty that motor. That sound could have been the lifters or any number of things and to just blame it on piston slap right away isn't the right course. Did the engine have good oil pressure, that is known to cause a knocking motor LOL. J/K man, I would bet with the cooler weather we have been having in the DC area it is just probiably the lifters particularly if you haven't started it in a week or two. If the sound were coming from the bottom end I dare say it is something worse than piston slap being you probiably have quite a few miles on that motor by now.

Black Z/28

Nicely said.

nick y

iTrader: (1)

i agree100%

nick y

iTrader: (1)

i agree 100% with above statement, man its noisy when cold out big time!!!
once engine oil hit 180 ok termal expansion you know!!!!!!!!!

evil02z

It's an inherent defect due to the piston design. The LS series engines have a shallow piston skirt design. Depending on the engine clearances the piston will "wobble" in the bore. This usually happens on cold starts and goes away after the engine heats up and the engine and components expand. The LS6 engine haves teflon coated skirts so they usually don't have this problem. If a piston is replaced under warranty GM will send a teflon coated piston wether the engine has teflon pistons in it or not.

Benjamin Russick

iTrader: (1)

evil: I've been saying that for years... It's the same reason forged pistons are noisy until they warm up. Now if you have serious "knock" issues after warm-up, replacement is justified.

ActionJack

I do not have this problem at all. But I heard the sound byte and it sounds like ****. If I had that I would definately join the class action suite. Basically, all you are doing is signing a paper as being one of the plaintiffs and then the attorneys do all the work. I do not believe you would have a class action suite unless there was very good evidence since the attorneys make no money unless it is settled or won and they spend allot of money and time to persue. GMC will end out owning the problem in some form.

jerflash

i have light slap at startup
but when it warms up u dont hear it at all

never burns oil either

maybe people sould stop using thin *** mobil 1 5w-30
use amsoil 10w-30 turbo formula its the best oil out there