Yves, for a honest comparison you have to factor in that the US classifies fuels in PON, pump octane number. We have RON, Research Octane Number. PON = MON+RON/2. MON = Motor Octane number and as higher than RON. As a result PON is usually a good amount of points higher (around 7 I think), so our RON95 and RON98 are pretty crappy.
I was thinking something along those lines. If i believe our 98 is something like their 87-90 octane fuel.
Since i have to buy me a new engineblock, going back to the stock 400 bore and since my pistons were scuffed, i need to figure out which dome i'm going to use. I have basically 2 choices 3cc or 8cc dome. Then there is the deck height to decide upon. If i'm going to a zero deck, and use the head gasket as head to piston clearance.
FWIW these are the numbers on my cam :
278/288 advertised mech. roller (246/256 @0.5, valve events intake 14° BTDC/52°ABDC, exhaust 64° BBDC/12°ATDC, lobe seperation intake 108°, exhaust 117°). (cam was optimised to the longer rod, short stroke combination and the 10/1 CR i had with the previous enginebore.
Heads are Dart pro 1 alu 215, 64 cc chamber. Chamber turned out to have 70 cc actual volume.
When calculating CR with no mods to deck height, the SCR with the 3cc dome would be 9.8/1 (DCR 7,8), with the 8cc dome 10.39/1 (DCR 7.95)
When doing the same, but the blocked decked to "0", the SCR with 3cc dome would be 10.44 (DCR 8.30), with the 8cc dome 11,12/1 (DCR 8.81)
There is only one thing i left on the table and that is deshrouding the valve. Due to the larger bore of the 400, i could do some serious deshrouding of the valves, which would enlarge the head volume and decrease CR somewhat more.
However, i would think the 8CC and zero deck is way to high, the 3cc with zero deck could be borderline.