400 Heads

[dnice386]

Hi, I recently accquired a 72 350 motor. The guy I got it from said the heads are no good, but he had a set of 400 heads sitting around. I was wondering if anyone know whether or not the 400 heads can be put on the 350 motor. This guy thought they might work, but he wasn't sure and I have no idea. Thanks

[MrPbody]

dnice,

It depends on WHICH 350 or 400 heads. One of the MOST desired iron heads for a 455 is the '76-'79 350 "6X-4" head. It isn't real valuable, but it has potential. When properly ported and upgraded, it can make more poewr than most others, on a "low" (9.5:1) compression 455.

ALL the heads have the same bolt pattern at the block ('55-'79), and '65-newer 389, 400, 421, 428 ande 455 heads use the same intake pattern, as well. All the non "Ram Air" or "Round Port" heads use the same exhaust flange, too.

Get the casting numbers from both sets. It's found on the outside of the center exhaust ports, where they protrude from the head. Post that, and I can tell you which would be better.

It's best to explain here, Pontiac V8s are "different" than Chevy and Ford. Bigger is not always better. A set of 455 heads would KILL the power of a 350 (makes it about 6:1). Most Pontiac d-port heads are based on identical castings, with slight variations on the theme. Some have larger valves than others, and still others have smaller combustion chambers. It can be a big bag o' worms... Post the numbers and I'll get you straight.

Jim

[dnice386]

Thanks Jim,

So if I understand you correctly, hte 400 would fit, because they;'ll bolt onto the 350 block. But I would need to get an intake for a 400, because the bolt pattern for the intake would be different between the 350 and 400?
I'll get the numbers and post them as soon as I get a chance. I can easily get the 350 numbers because I have th emotor, but I'll have to call this guy and ask him for the numbers on the 400 heads. Thanks for your help.