Why doesnt the cam card have spring specs? How tight are the valve guides? If you split a lock what does the associated groove look like?
It looks like the tip is getting it's as$ kicked for a short duration of RPM. Have you ever found valve float RPM? Maybe if it isnt getting beat to death the guide is sticking keeping the valve from rotating causing the pattern? Is that roller on the rocker smooth in operation?
If that close up is a Ti intake it almost looks like the tip insert is coming out. Lack of lash could make things ugly too.
I'll get you some more info. I'm going to finish disassembling the heads, check all the valve spring pressures. The guides were not tight by any means, but I'll check the actual clearance. I don't know what the cam card doesn't have spring specs.
