I began getting a metal rattling sound when the motor isn't fully warmed up on cold mornings. It happens under hard acceleration at like 4000-5000 RPM's. It goes away when the motor is fully warmed up.

I'm thinking this is piston slap that goes away once the piston warms up and expands. I thought, however, that the pistons in our motors were hypereutectic and didn't expand much. I've heard of this being common on forged pistons but not the hypers. Other than that engine runs great and I haven't noticed any degradation of performance. Could it be a cracked piston??

Is there a Technical Service Bulliten (TSB) for piston slap or failure? Anyone experience this?

Thanks.

 

are you sure what your hearing isn't spark knock? If you don't know for sure I'd stay out of the throttle until you find out. You can always return to stock and see if it goes away.

 

Spark knock is an interesting thought. But it only happens at higher RPM's and when the motor is cold. I guess I should just stay out of it until the motor reaches operating temperature. After it warms up everything seems fine.

 

If you have a laptop, you should be able to hook it up with your predator and monitor the knock sensors to see if they are detecting knock. you can also monitor your spark timing to see if it is pulling timing like crazy when you hear the noise. I have never tried it with a predator, but with my sct xcal II, it is really easy.