[cttempest]

Originally Posted by Donovan

Don't use 400-455 heads on the smaller 350 bore. The chamber cut at the top is cut wider and more shallow to match the bigger bore. This area will have headgasket extending into the cylinder volume on the small bore. 350 Bore is 3.875. All these heads should be used on 4.03 and larger.

Find a 68-70 350 head.

17, 18, 47, 11 are GOOD

Small chamber 400 heads are BAD. Like 12, 13, 14, 15, 16, 45, 46

ONE EXCEPTION - 670 heads. They are closed chamber and don't have the top scallop cut that creates the problem.

Keep in mind you also need to use the correct 350 head gasket for the same reason. The common Pontiac gasket has a cutout at 4.2"

Tom S. is using these on a larger bore engine than your 350! I see Bruce says he has used these on a 350, but even if he got away with it, I respectfully suggest it is not good advice.

Dammit,ok,not what I wanted to hear.

I commited to buying a set of 15's from a member here.It makes sense about the chamber cut,but I was running 326 heads before,which are an even smaller bore??, and it ran fine.I have the head gaskets here and everything seemed normal after teardown.

I HAVE a set of 670's that I had redone years ago from my 400 that I know are in great condition ready to go,but I've been warned to stay away from the big valve heads(2.11/1.77) on the 670's..If theese are the heads to use than awesome,but it just seems like too big of valves.