273 Question.

Exactly right on the lower CR and open heads. The last thing you want with any pressurized system is too much compression; with boosts in the 15 psi range, the compression pressures jump well above 200 psi even with low SCR's. The open heads are the right pace to start, and you may even want/need some dish top pistons. I don't know how much pressure this blower makes; I assume it can be geared/belted up or down to get the desired pressure. (Oh yeah, I see you are looking at that.) But that will play into the CR desired.

Just shooting from the hip with one data point..... We use a true 8.2:1 SCR on a turbo Starion 2.6L engine with 14-15 max turbo boost, and that is pushing above the stock factory CR levels which were an abysmal 7.3:1, but were all-around safe for up that level of boost. Our engine gets hammered as a rally car engine, so it has to be a bit on the conservative side. 8.2:1 may be on the edge of too much for a blower setup, since you can get lots of pressure down at low RPM's.

And if the valve-to-block clearance is a problem, I would consider using open 318 heads. The blower will make up for the smaller runners and valves at low and mid RPM's and even to some extent at higher RPM's. A thinner rather than thicker head gasket should also be a consideration. Might be a good place for a Cometic, though our Starion does just fine with a stock Felpro composite.

Sounds like a lot of fun!