I have a 1969 firebird 350 with #092 heads. I found that these were heads found on a 1966 389 and 421 motors. My question is, is this a good combo? I'm worried the bigger heads with cause lower compression.
Hey, I suppose that if it runs good, they must be OK. I think all these came with press-in studs. I'd want screw-in studs on any engine. I think the valves are at a different angle than 350 heads. But, unless you run a really big cam, I suppose the valves will not hit the pistons. And, if you have press-in studs, you don't wanna run a really big cam, anyhow. Piston deck height & head gasket thickness also come into play, when determining the valve to piston clearance. Lots of guys have run the '68 #17 & '69 #47 350 2-barrel heads.
Adam Strang ran 10.80's with his '68 Stocker, running a 350 with the #18 '68 350HO heads. As most know, the '69 350HO had small chamber #48 big valve heads. For a 350, the big valves are not needed, as Adam Strang proved.
I would assume that 72-75cc chamber heads would be compatible with today's pump gas, on a 350.