Dave,
My thought would be if you don't have the answer, I sure as heck don't, but that has never stopped me from sounding off before.
Were the valve spring pressures checked when the head/engine was rebuilt. I had the same issue on a SBC and it turned out to be weak valve springs.
This would be a perfect troubleshoot for a scope. Good luck
Stuart
Last edited by atomarc; 06/03/2008 10:59 PM.