Ok here's my best guess
the lash is spec'd at .015 VALVE lift, which back thru the rocker-arm ratio of 1.5 equals .010 TAPPET lift. So your engine will never see any duration listed at less than .010 tappet lift....... so long as the valve lash is .015 hot. Your card does not specify hot-lash.
Ok so say you lashed it hot and the .010 spec is right.Now on the card the duration from .010 is listed at 318/291 This is not advertised, this what I extracted from the card, and is what your engine will actually be seeing. So let's call it a 318/291/108 in at 104 per the card, this yields an ICA of 83*
This does not work out right in the calculator, requiring more than 13/1 Scr to achieve your pressures...... which would require a TOTAL chamber volume of 52cc @3.43x4.125. And I ain't buying that.
So bottom line is My head is against the wall. The only way I can help you is if you actually do the work of measuring the total chamber size, and also go to the trouble of establishing the ICA by finding it in the assembled engine.
But it's kindof moot because we have already established that your engine was detonating at the current pressures of 175 to 215 was it?
With this combo valve lash is critical.
And here's why; If your hot-lash was actually .030 at the valve, which is .020 tappet lift, then your intake duration falls to 254* and makes an ICA of 51*... which pulls your pressures into line at about 10/1. 10/1 seems more likely with your machining.
However, a hot-lash of .030 would be pretty noisy.
So at this point, you are looking at a pretty expensive repair bill.
Don't forget to have the rods checked for straightness,as well as the deck and head.
Also recall that I just guessed that the pressure during detonation lifted the head, and cylinder pressure escaped into the cooling system; it is a guess. If you don't pressure test the head and block, then you won't know they are good.
I would also replace the headbolts now, just in case they were overstressed. Cuz if you don't, and this happens all over again,you're gonna be saying;" why didn't you tell me?"
