Flat top pistons with closed (quench) chamber heads is a more effecient setup that domes and open chamber heads for the type of rpm and flow rates that you will see in a 2F. Any 2F.
If you run flat tops in the open chamber head, compression drops a lot. Bad thing. If you run domes in the closed chamber head, the piston and the head try to occupy the same space at TDC. Worse thing.
If you want to run the earlier head, mill it to reduce the volume of the chamber to bring compression back up some. In the real world (as opposed to the dyno) you will never notice an difference in power or economy over the later head with this approach. But if you start with the later head and mill it too, you can attain higher compression.
Does anyone have a good photo of a domed piston versus a flat top?
I read over several 2F builds but the only clear pics I found are of engines that should have flat tops (Trollholes and Andrew Farmers). Both engines have pistons with a slightly raised center that is circular.
I am rebuilding a 2F that came from a canadian spec '78 FJ45. It appears to me that it has a flat top/open chamber combination. The pistons look just like the ones mentioned above. The chambers are oval not kidney shaped. I will probably just mill the head to increase the CR.
