why do ls1's make that tapping sound?
 

ive always wondered why our engines make a tapping sound on cold start and pretty much all the time? it dont get louder when i accelerate so i dont think its anything serious,but remember reading before that its common. why?

That tapping sound is called "piston slap" and is a result of aluminum expanding slower than the iron cylinder liners.

The reason you hear it well is because you have an aluminum block in your car and not an iron block like in your dad's work truck.

Ben T.

:judge: :judge: uh ok thanks but tell me something i didnt know :)

piston slap, all our lsx motors have it. the reason they make the noise was already explained

When your engine is cold,the piston takes an oblong shape.During this time,their is more clearance between the piston and the cylinder walls.As the Crankshaft turns,the piston rocks back and forth slapping the cylinder walls. The noise is from vibration.LS1 cylinder walls are very thin so that amplifies the noise you hear.As the engine warms up,thermal expansion occurs and the piston/cylinder wall clearances becomes less.The result,piston slap noise goes away.I dont know if that is what you are looking for???

Piston slap is normal on an LS1...You will be fine

otay! :wrist:

You asked what it was... the man explained. :bang:

lol thanks guys i just wanted to make sure haha :)

(lol) :confused: Why did you ask if you already knew why it causes a tapping sound?

lol i didnt mean to ask a stupid question,lol i have a bad memory and forgot ahahha,but i knew that its called piston slap and that we have aluminum blocks i aint one of them so called idiots........ or am i lol

No,I think we all forget some things over time if we do not use it or discuss whatever it may be.

I think most of it is in the valvetrain. My iron block 5.3 does it all the time, even when hot and so does my dad's iron block 6.0. I don't think this is piston slap. Oddly, my LS1 does it when cold but it's the quietest out of the 3 when warm.

It gets louder when you raise the compression ratio :bang: