RV7A now at 230 hours. Engine is based on the Subaru STI engine but has longer stroke crank and custom pistons with 10.4 to 1 compression and 2.6 liter displacement. The engine is now naturally aspirated, but it has been boosted in the past via roots type supercharger, and then turbocharger. Both of those installations had problems with reliability, but with stellar performance.
Now running normally aspirated 2.6 liter STI based engine with longer stroke and custom pistons bringing displacement to 2.6 liters. I believe my engine and Rupert Clarke's engine are very similar, assembled by Maxwell Propulsion.
Cooling in the hot conditions in the California "Valley" has proven to be just fine using NPG plus coolant and a 4 PSI radiator cap. This is a plus as it allows a nearly no pressure cooling system, eliminating much stress on the hoses and connections, and the boil over potential is practically eliminated.
Normally aspirated performance is a bit disappointing after having two different boosted applications in this airframe, but reliability is now excellent. Previous boosted installations achieved VNE speeds at 8000'. Current cruise performance is in the 150 knot range at 8000', it will top out at 164 knots.
Fuel consumption seems pretty good, giving me 140 to 150 knot cruise at 7 to 8 GPH.
Randy C