Do the same quench rules apply on big bore (4.125 or 4.25) small blocks. Seems the good number is about .040 ish for std bore. Also, can you still get away with 12:1 and 9:1 DCR on the big SBC motors with traditional cooled aluminum heads,93 pump gas, and EFI of course?

 

Yes, same rules for quench apply.

I am running 8.8:1 DCR in a 457 ci small block right now and the engine is very happy. This engine will never turn enough rpm (peaks at 7300) to ever have issues with flame speeds in its 4.2" bore.

You should take a few precautions though if you want to push the 9.0 mark. In my engine, I had Swain coat the combustion chambers, exhaust & intake valves along with the exhaust port. If anything, I'd always at least polish the combustion chambers, coat the exhaust valves with the exhaust port and make sure there are no sharp edges on the pistons.

If you decide to go with a head that has optional cooling to the center exhaust port pairs... take advantage of that. The sb2.2 and many splayed heads cool much better in that area so they don't need it.

-Mindgame