Hello all. I'm new to the board and I guess ls motors. I've owned a 2002 silverado z71 for 7 years but never had to do anything but routine maintenance on it. I joined this board for 2 reasons 1) my 5.3 in my truck has developed what is called piston slap that is driving me totally nuts. I hate it. 2) i am building a MK4 roadster(cobra kit car) from factory 5 and plan to put a 6.0L and 6 spd in it. This car should be fun to say the least.

Anyway back to why I posted in this section. I want to build another 5.3L for my truck. What aftermarket parts or factory parts can I put in to eliminate the annoying piston slap? Kinda thinking I might do a little more to motor also for the 4x4 side of it. I have a 4" lift and running LT285 mudders on it. I was/am thinking all good aftermarket rotating assembly - would that get rid of all possibilities of any piston slap in the future? I have already bought a 5.3L , just have to go pick it up, its mostly all there. Its missing the crank. It came out of a truck - iron block alum heads. Also comes with a extra set of 6.0L heads.

Well thanks for any ideas you guys can throw my way on this rebuild.

 

Are you getting this sound only when cold or when hot?

 

cold - then it warms it goes away. Usually only lasts about a minute or so.

 

That's short piston skirts on many of the LS motors. Most folks just deal with it but you can make sure to get pistons with longer skirts to mitigate this effect if you are going aftermarket I believe. Some skirt coatings can help with this a little and even reduce wear from my reading. I am unsure what factory parts are better for this than others, if any, but short skirts are supposed to be the culprit. Once things warm up and expand, clearances are tighter and the noise goes away.

 

Its probably lifter noise, most people won't know piston noise if it slapped um....... Piston noise sounds EXACTLY like a diesel engine and it doesn't go away in a min or so. Lifter noise sounds like a **** load of tapping that's lasts a few mins.

 

I don't believe everything I read on the internet but it seems that there is a lot of evidence of piston slap for 1-2 mins until a motor warms up. Are those folks wrong or is that situation just rare?

Thanks

 

Either way - I'm going to build a new motor for it. Plan on aftermarket rotating assembly new lifters maybe a cam upgrade the trunions on the rockers, you know fix all the problems that are known about these motors.

 

Spending $3000 to build a forged short block because you have either piston slap or lifter tick sounds like a expensive solution to something that isn't really a problem. Their are motors that have had these problems from new and still run for 300,000 miles.

 

That's true fry - but it drives me nuts hearing it. It don't have to be a forged assembly - I could do a stock crank and aftermarket rods and pistons. Like I said before - I kinda like to do a lil more power/torque with it being a lifted 4x4 with bigger tires.

 

Go buy a LQ4/lq9, put cam/springs/tune in and call it a day. My 5.3 was doing the same thing yours does but would only do it first start of the day.

 

Like I said very few know what piston slap sounds like. You think pistons warm up enough in 2 mins to expand enough to be quiet? Do you think piston slap noise actually goes away? If it ticks and taps and raps for 2 mins you got lifter noise........... piston noise sounds ECACTLY like a diesel engine and never quite goes away completely. Is inherent in these engines because of the short piton design. I can tell you this much, If you hear a piston knocking its not going to last for very long.

Most dealers will ALWAYS say any engine noise is piston slap. I've owned 5 of these cars and every dealer tried to tell me the ticking and tapping cold was "piston slap" BULL ****! Its GM's way of not fixing their PIECE OF **** fast bleed down lifter design.

ALL of the engines will have piston noise BUT YOU DON"T KNOW WHAT YOU ARE HEARING. Its that rocky low diesel noise these engines make no matter how warmed up they are. You have to listen close and know what you hearing.

 

Interesting. Wouldn't be the first time everyone was wrong because they all read each others' posts on the interwebs!

I guess I am lucky on my first LS to have a 5.3 of completely unknown origin or condition and no tapping, clicking, slapping. Also nothing that sounds like my diesel. Though I have heard it making kissy sounds at me when I am looking at prices for heads.

 

i would describe piston slap as a light tapping at idol but if you rev the TB to say 2k rpm its gone and purring like a kitten. a lifter noise would probably get worse. i've heard piston slap on my car & and on a fresh TPIS rebuild on their shops dyno.

 

How does it compare to spark knock? I definitely remember tuning advance by that noise in old-school cars.

 

I got piston slap on my 02 Z71 with 189k miles on it. Idc it still runs great besides sounding like a diesel when i crank it. After driving down the road between my Windows being down or the AC and radio going i cant hear it at all. Thing is once the truck is paid for thats when ima build it. I know its only a 5.3 so i don't plan on making much power

 

I'll say it one more time.......piston NOISE sounds exactly like a diesel engine but not near as loud. The GM dealers have been groomed by GM to blame lifter noise as piston slap because piston slap is "normal noise"


I'll give you an example, I bought a used 01 WS6 engine was noisy as hell tapping and rapping nasty as hell. Cold it was insane, warmed up better but still loud. I take it back to the GM dealer I bought it from. They claim its normal piston slap, I take it to another GM dealer they say same thing.

Well I just didn't fall off the turnip truck, If pistons were rapping and knocking that loud all the time there would be BLOWBY and in no time extreme damage to the pistons and cylinder walls.

I take it to a 3rd GM dealer with a old time service manager been in business 40 years. Says as soon as he hears it you have dirty lifters, told me to try changing the oil a few times maybe it will get better.

Take it out to a well known EXCELLENT performance shop near me that does mostly LS1 cars. Chief wrench listens for a min and tells me LIFTERS, told me try some good synthetic oil that may clean then up. Changing the oil helped a little.

I finally got rid of the "PISTON SLAP" noise by using a product called Rislone. Its a oil additive that cleans the lifters...............

Another problem AND the most common noise these engine have is COLD CARBON KNOCK....YES say it 3 times COLD CARBON KNOCK. This noise is the most common one that is called "piston slap" When the engine is warmed up to running operating temp carbon slowly builds up on the pistons and over time builds up thick enough to contact the cylinder head when the engine is cold.

So you start the engine cold and the carbon built up on the pistons is hitting the tops of the cylinder heads making ALOTA noise but as the engine warms up it EXPANDS ALOT and the carbon no longer touches the cylinder heads and its quiet as a mouse. This IS THE MOST COMMON problem and ALWAYS diagnosed as " PISTON SLAP"

Now I'll tell you a little story about this, 99TA had PISTON SLAP bought it with 28k on it. Drove it like that for over 75k until the dealer did a engine carbon cleaning because of poor performance..........NO MORE PISTON SLAP NOISE!

PISTON SLAP IS A BUNCH OF CRAP.............no such EFFING thing! Might be extreme case here or there but ITS FARKING BS!