I have about 100k miles on the engine at this point, and when cold over 8 hours or so the engine has a load related knock after start-up, which seems to be a piston. In about one or two minutes after start-up it is gone, and I am assuming this is a piston slap. Has anyone else experienced this, and if so, for how long? In other words is the condition fairly benign, or does it indicate that the engine should be bored over?

 

I'd say its pretty common for gm motors at cold start up.. Could be the rockers til the oil gets up there.. My car makes a little chatter at start up as well. But like you said, its gone within a min or two ..

I wouldnt worry about it ...

 

Yes, I know the sound of the rockers, and they are noisy on these engines. But this sound is load related. Tip into the throttle, and one, perhaps two pistons rattle (like a quiet diesel), but when you back off the throttle, quiets instantly. And then it goes after about a quarter mile of driving.

 

Yes mine does it from time to time especially when it is colder. I was living in TN and in the winter months especially a colder (cooler) day it would make like a pistion slap noise for a few minutes. When I blew my head gasket and had the heads off none of the cyclinders had any noticable marks so I gues it is OK.

On warm days no noise only on days around freezing or slightly over. Where I am now the car is tucked away for another 2.5 to 3 mnths as I will not let my car see any salt.

 

I dont have that on mine.. Maybe it is a little more serious..

Hows your oil pressure ?

 

Mines done that ever since I got it when cold. I got it in 1999 with 29k on the clock and now has 72k with no ill effects. When its cold outside I just let it warm up for 2-3 minutes or go easy on it for a few if I dont have the time for a warmup.

-Tony

 

I think its normal... the 350 in my truck (at 180k) does that if I dont give it a chance to warm up (its a matter of life or death to be fast out the parking lot at my school).

My camaro always gets a chance to warm up, so I wouldnt know for sure.

 

proper warm up is arund 1 minute.

 

My new 383 does it also. I had the shop use a .0045 skirt clearence and it rattles farily loudly for about 2 or 3 mins. Then it eventually completely goes away. This really bugs me but I guess there is nothing I can do about it now. They are forged SRPs . The manufacturer called for .0035 for NA cars but i called them and told them i would be running 150 shot and they recommended and extra .001 Does anyone know if piston slap on a cold motor hurts anything?

 

My car does the exact same thing. Loud ticking noise when given to much gas, it only did it when the engine was cold and lasted for about a mile. Then it would go away and make no noise at all and I have great oil pressure.

 

Both of my cars... well now only one since I sold my Z, have had the piston slap noise. Its a deep sounding noise not like a lifter or rocker arm, and goes away in a few minutes of driving. I did some research on this and found it to be pretty much normal if in fact it is a piston slap noise that you are hearing.

 

Minor piston slap won't hurt a thing,just annoying.