Going to the domed pistons with the 64 CC heads will put you into "racing gas only" territory- - - -100+ octane or so. Even 10:1 is pushing the envelope unless you're running a fairly radical cam. Here's something wannabe engine builders don't realize- - - -the ONLY reason to use high compression pistons is to compensate for a very long duration camshaft. That 11:1 piston needs a 300+ degree duration cam to work right, and you'll have virtually no usable torque below 3K RPM. The actual compression PRESSURE (not ratio) only needs to be at, or slightly above the pressure developed in a stock engine with a short duration cam, but since the intake valve is closing WAY up the compression stroke with a radical-grind cam, the remaining cylinder volume must get squeezed tighter just to get back to where it used to be when the engine was in stock trim. In the process of gaining some top end horsepower at speeds the average street engine never sees, you're losing massive amounts of low end torque. Why in the world would anyone want to pair up an engine that gets its usable horsepower somewhere around 5K RPM with a SM-420 transmission?
I'd suggest using flat top hypereutectic pistons with the 64CC camel-hump heads, and a Comp Cams 268H hydraulic cam that still has good low-end torque, runs well on pump premium or maybe mid-grade gas, and will wind to 7K+ RPM before it starts running out of breath. Be very sure to install screw-in rocker studs and guide plates and do a good 3-angle valve job with some pocket porting to free up the high RPM breathing capabilities. One of my students built an engine like that which turned out 400+ HP at 6500 RPM on the dyno, corrected for temperature and humidity- - - -real numbers, not a bench-racer's pipe dream. He put it in a Chevy Monte Carlo, and routinely ate 5.0 liter Mustangs for lunch at every stoplight.
Jerry
