"...1967 #143, 1966 #093..."


Not familiar with those older heads, and never fooled with any 389 or 326 stuff. I assume that the #093's are closed chamber. Some '67 heads were also closed chamber.

I think the valve angle was different, on pre-'67 heads. ??? Engines which came with the different valve angle, had valve reliefs in a slightly different location. As the cam gets bigger, and the valves get closer to the pistons, for whatever reason, valve size & angle, as well as valve relief location, come into play, for determining valve to piston clearance.

I read about one 350 build that used closed chamber 326 heads. Don't remember the head number or size of cam used. But, it ran pretty good. It was probably quite common for guys to use 326 heads, to increase the CR.

I personally would prefer to use open chamber heads, with the later valve angle.