brettleh

Would gt40 heads even fit my pistons? I would have to cut my pistons with a grinder to fit any valves?

craig71springsport

You really do not want to do that. First off, cutting valve reliefs into pistons creates thin areas, which will be weak points in your pistons. You will most likely have a failure at those points. Maybe not right away, or even for a little while, I have never done it so I do not have first hand experience, just have heard horror stories. They will either crack or blow out at those points if your compression is high enough.

Secondly, your pistons are cast. As you upgrade an engine, your compression ratio will surely go up, meaning you'll want forged internals. So, cutting valve reliefs into cast pistons is a double no-no. You will want to buy aftermarket forged pistons. They are designed to allow valve clearance for the nastiest of cams and still be strong enough to not blow apart.

tinman

NOPE...
Those heads are big enough in the port department to use on a 408.
They would be a disaster on anu 302-306 type engine due to the huge ports/valves.
My 352 all-out drag race motor couldn't even use them........