Help diagnose noise

[Pete O]

I know it's tough to ask someone to diagnose a noise without actually being able to hear it, but here goes. I have a noise coming from low down and toward the rear of the engine. It's sounds like a hollow metalic knocking- kind of like, if you could imagine, the sound a hard rubber mallet might make if it were banged against the inside of the oilpan. It's most prevalent right after a cold start. It's not there at idle speed. But if you slowly bring the speed up, it starts at maybe around 1500 rmp. But if you rev it fast, it's not there. The sound almost goes away when the engine warms up.

What might it be? Could it be piston slap?

Thanks for any guesses!

Pete

[JohnD1956]

I had a 78 once with what was described as piston slap. It was like a door knocker knock which never went away when warmed up. I only heard it as I was accelerating, never at an idle.

If you have low down noise and dull knock, I'd guess harmonic balancer.

JD

[sledheader 48381]

Pete; Is your car an automatic, I have seen newer model cars with autos that have cracked flexplates[flywheels] and when the engine is accelerated it causes a knock,sounds just like a bad bearing.

Just a thought Don

BCA # 40498

[Pete O]

I does have the Dynaflow tranny. Thanks for the tip! I figure I'll drop the pan to check the rod bearings over the winter, and clean out the pan and inspect the oil pump while I'm at it. But if the rods check out ok, I'll know what else to check for now. Thanks again!

Pete