Hughes is making sure you don't get any quench benefit from the piston dome. They are milling the head down to 62cc (spec is 65-72??), then they are sticking in a thick head gasket (.054).
Why not less milling on the heads to preserve head gasket sealing surface strength, and run a thinner head gasket? Even the Hughes ad says they are using a 0.039 head gasket with the pistons they recommended to you.
Feed the Hughes numbers into KB calculator:
Result is 9:1 static and 7.5 dynamic. Pretty conservative for cast iron heads. Are you planning on regular grade fuel?
head volume 62cc
piston volume 19.4cc
gasket thickness 0.054 inch
gasket bore 4.08
cylinder bore diameter 4.03
deck clearance 0
stroke 3.58
rod length 6.123
intake closing 60*abc
My old work truck is running 9.6:1 compression with iron heads, 0.045 quench, and can pull a 8k lb trailer weight up any hill without knocking....all with the cheapest regular gas from the pump.
Maybe go over the Hughes info with your engine building buddies...
Here is another option using the KB flat top pistons you already have, and your cast iron oem heads:
Result is 10:1 static and 8:1 dynamic; better than the Hughes example IMO. Would need premium fuel, but also leaves you open to aluminum heads in the future.
cast iron head volume 65cc
piston volume 7cc
gasket thickness 0.04 inch
gasket bore 4.08
cylinder bore diameter 4.03
deck clearance 0.01 (below deck)
stroke 3.58
rod length 6.123
intake closing 64*abc
OR...change the KB flat top example above by increasing the cast iron head combustion chamber volume to 67cc, and close the intake valve sooner at 62* abc; result is even more streetable at 9.8:1 static compression and 8:1 dynamic.
HOw to increase combustion chamber volume...simply unshroud the valves for better port breathing can give the 5cc increase. OR...let the piston be a little lower below block deck at TDC, rather than the 0.01 number I used.
Just some ideas.
