I was looking at having the block decked but keeping the pistons. 020 below deck. And running 15cc dish pistons. As well as a .040 compressed head gasket thickness.
The effectiveness of quench can be a bit counter-intuitive at first, and so I can understand how it might seem that leaving the pistons in the hole woudl lower compression and thereby reduce detonation, but the resulting lack of quench actually makes detonation
more likely. And so conversely, while zero-decking the block may increase compression ratio the simultaneous increase in quench effectiveness greatly surpasses the modest compression increase.
If my calculations are correct that should bring it to around 10:1. I wouldn't mind splashing some 100ll into it. Or even keeping race fuel on hand to add in at every fill up.
OEM early heads are typically 77cc's from the factory; with the addition of large valves the chamber volume drops to about 74cc typical. Any chance you're porting the heads yourself? If so, perhaps you can grind/shape/polish the combustion chambers and get about 5ccs back into them, to about 78-79ccs. If so, then c/r would drop to about 10.1:1 with the Icon pistons I mentioned earlier. Might be a long way to get there but if you're motivated/enthusiastic about doing your own stuff like I am then it's not so bad. PS: Check the heads for flatness and if they don't need surfacing then bypass that step since it lowers chamber volume as well.
