I also thought that the 65 273 heads were closed chambers, weren't they? Oh, buy they way I'm running a 65 forged 273 crank in my 340 with mallory weight added of course. I wished now that I could of went a stoker crank, but..........
They are closed chamber but aren't the intake bolt pattern slightly different on the 64 - 66 heads? I heard that the 67 head is the only head with the closed chamber but has the later style intake bolt pattern, any truth to that?
I put a poly 318 crank in my 340.