A friend of mine just got done putting a 400 HP 302 in his car, well he drove it about 20 miles so far, and he had some valve train noise, so he sent it to the local speed shop, and they adjusted the valves, he has an aftermarket roller valvetrain. Well it has been about a week and 10 miles later, and now the engine has a terrible knock at idle, he has good oil pressure, and he said when he revs it up the knock smoothes out and ends, how do you explain this? Any suggestions on how to narrow the problem down would be greatly appreciated. Thank you

 

First, is this a valvtrain knock (same type as before)? Or is it a new lower end knock?

What kind of lifters, solid or hyd?

It MAY be, if hyd, that the lifters are bleeding down at low rpm. When the rpm's increase the lifters pump up and take up the slack.

If the valve adjustment worked at first then it started it again.............bad news, the cam is going away.
If this is the case, a few questions;
What was the cam break in procedure and what cam lube was used? What are the valve spring pressures (open/closed)?

 

It could also be that he overtorqued the rod bolts (we have a 302 that this happened to), it knocks at idle but clears up with RPM.

 

could be cold piston slap. let it warm up and see if its as bad.