Long-Slot, Stamped Steel Rockers

[clockdoc]

I have a question for you engine guys. I have recently installed a built 327 in my 1978 C10. I have had an issue with valve train noise from the getgo. The engine is running an Edelbrock 7102 cam (.488/.510 lifts) and Proform, long-slot stamped steel rockers with stock-length pushrods. I finally determined that I had some rockers hitting the manifold-side of both valve covers. Installed fabricated covers which eliminated the rocker interference but still have what I think is more than normal noise which increases as the engine heats up.

My question is are long-slot rockers inherently noisy? I have no previous experience with them.

Any observations will be appreciated.