Can pontiac 326 be fitted w/ 400 heads?

[Ronnie]

I've got pontiac 400 heads from a previous motor that is no longer with us(R.I.P) and pontiac 326 ready to go. I heard someone say once that all 326- 400 had enter changeable heads and manifolds. So, here's my question can my 400 heads fit on my 326 and what kind of horse power increase can I expect if its possible?

[Romanticrocker]

I'm pretty sure they'd be interchangeable. The 326 is a de-bored 389, and a 400 is an enlarged 389. They should work just fine, but I'm not sure what kind of increase you can expect. It probably depends on what type of 400 it is. A set of 1974 400 2-barrel heads won't flow as well as 1969 400 4-barrel heads from a GTO. If they are high performance heads then you should build the 326 to match them with a hotter cam and performance exhaust system.