For a 512" street car, 3.55:1 gear, and 4-speed, I was being conservative on compression ratio for a few reasons. One is the chambers of the RPM and Stealth heads do not have as much quench area as the small chamber heads like the Victor or B1 B/S, also the spark plug location of the Stealth has not been relocated closer to the chamber center like the other heads. They may also want to use a really mild cam less than 240 @ 0.050"?, the 512 will still have plenty of torque because of its size, the engine will be more tolerant if using lower octane fuel.
The 24cc dish pistons on a 512, zero deck, 0.040" quench (head gasket) with 84cc heads is still 9.88:1 compression. The 17cc dish pistons are 10.44:1, and the flat tops with 4cc valve reliefs is 11.69:1 compression. Of course you can always get custom dish pistons for extra $$$.
I used 84cc for the head chamber size, because that is the RPM and old Stealth size. The new Stealth heads are reported to be 80cc? so that would bump the 9.88:1 compression to 10.19:1.
The dynamic compression with something like the Solid roller Comp XR286R should have a dynamic compression around 7.3:1 to 7.5:1 depending on the actual compression ratio, cam installed centerline, and valve lash.
One thing of note is that the block had been milled to set the piston even with the deck so quench equals gasket thickness, If the piston is setting below the deck or using thicker gaskets, you loose much of the quench benefits.
FWIW, I have ran my 12:1 compression 500" stroker on pump premimum on the street (I use race gas at the track to be safe), but it has smaller chamber heads, a 0.714" lift roller cam (dynamic compression is only 7.45:1) , high stall converter, 4.10:1 gears (was 3.91:1), and I run a 160 thermostat, and I am at 6,000 ft altitude. A part of running high compression on pump gas is keeping the engine and incoming air cool, and having a good tune.
Diamond Pistons allow 2 changes to the pistons before
they call them custom... I had them add more dish
to my set and it cost $35 extra for the set... might
be $40 now ... if he goes with Dan as the builder
I believe he uses Diamond quite often and can get
them tweaked for minimal cost
