upper rpm break up
This happens nearing the stripe, couple hundred rpm over the shift points. Its msd dist locked out at 34, I"ll try your suggestions Thank You!
So couple of hundred over 6300; well that could be valvesprings losing control; simple test is rev to same stripe-rpm in lower gear; springs are not usually load sensitive. So if it revs to stripe-rpm in second, it ain't the springs.
My 10.95Scr,tight-Q,aluminum headed, 367SBM, on the street, is happy at 34*. I found, by seat of the pants, no difference in performance anywhere between 32* to 36*, so 32/34* is what it has always run.
So then
I changed my mind about timing and possible detonation. 32* should be fine.
But overheated plugs would still be my #1 "idea".
And they may be that way from lean-running. And my experience with that is,that they never fully recover. So you could try fattening up the jets first , but I think, that's think, the plugs will have to be colder.
But before you do any changes, do the second-gear pull to stripe-rpm first, cuz you may be looking at a new rear gear.
It kindof depends on your cam.
