Piston Slap

**shlby123** · 01-15-2007, 03:21 PM

Still pretty green when it comes to most of these F-bodies and I was curious to gain a little insight on this phenomenon. I've done a couple searches on the site and on google, and was curious to see what some of ya'll say? Like, what are some of the typical tell-tale signs (if any) of a future occurence of piston slap? Are there many sure-fire ways to prevent it? And most importantly to me, does it occur in both LT1 and LS1 motors and if both which one has a higher chance of getting this type of problem. Any info would be so so appreciated!

**Sarge** · 01-16-2007, 04:08 AM

Well the GM engineers decided to make the piston skirts too damn short.....thus the slap of the cylinder walls....folks have tried heavy oil and oil additives to get as much film on the cylinder walls as possible....It doesn't really hurt anything in the long term....and performance isn't effected.....just a characteristic of the motor....

**shlby123** · 01-16-2007, 06:02 AM

Is it a characteristic that both the LT1 and LS1 can have?

**SSTODD** · 01-16-2007, 07:41 AM

LS1 is the only one I'm aware of but it is not something that happens over time but it is in the design as sarge said. It can be there from day one but it does not harm anything and is usually not there after warm up. The other thing is the people you kill are not near the front of the car anyway but looking at the tail lights.

**LS2Tuner** · 01-16-2007, 07:52 AM

It runs in the LS family. No the old LT1 does not have that problem. It has the regular big skirted piston so that wasn't a issue with that motor.

The best answer I've heard was a Service Manager dealing with a irate customer and he told him "Sir it's just part of your GREAT GM Feeling!"

It was pretty amussing I thought.

**shlby123** · 01-16-2007, 08:09 AM

LOL! very nice. Is there a difference in the block in an LS1 and an LT1?

**LS2Tuner** · 01-16-2007, 09:00 AM

YES, VERY MUCH SO!!!!

The LS is a whole NEW design! It is what we call a "skirted" block. It's like a big block Mopar. In plain english the crank in counter sunk in the block.= Much stronger design!
There is many other differences also.......... Too many to post quickly.

**YoMommasTA** · 01-17-2007, 05:32 PM

i drove a used 97 ta that had terrible piston knock until it warmed up.piston knock in gm HIPO engines is nothing new.The older vettes in the 70's knocked badly because of the piston fit.The pistons are fitted loose in the bores so they can get beat on hard without expanding and seizing.Sudden WOT in a HIPO engine cause the pistons to expand,if there is not enough clearance to account for this the pistons will not live long.Its actually a good thing.

**SiggyZ** · 01-18-2007, 12:02 PM

Both engines can do it but it is more audible in the LSXs due to their lighter weigh aluminum block as opposed to the LTXs iron block design. Many people confuse piston slap with lifter tap.