I'm with Don. I've made that mistake with motors in the past: trying to will away the issues or fix them with tweaks.
The problems you've been describing are serious and I'd hate to see you do further damage.
The head needs to come apart so you can get answers to the following
- Are all valve stems straight
- Get valve stem diams for all
- Get valve guide I.D. for all
- Is valve/guide clearance sufficient
- If valves or guides were replaced, are the materials compatible. Nitrided valves like different guide material than SS valves than stock valves. Guides come in many different material compositions.
- Are your spring heights and seat-off pressures correct?
- Are oil passages clear and all are passing sufficient lube
In other words. . . a full inspection / valve job.
Jason
