Magnum heads on an LA enigine

The number I hear most often is swapping magnum heads onto a 360 with no other changes is worth 20 HP. A 318 wouldn't be as much.

I am using magnum heads on an LA 360 but the engine was built with the heads in mind. The biggest advantage is the closed chambers, they allow you to run higher compression without the fear of detonation. My engine has zero decked flat top pistons and an 0.039" thick head gasket for a compresion ratio of 10.6:1 and it runs fine on 89 octane. I don't have a big cam either that bleeds off a lot of cylinder pressure. I just did a compression test last weekend and I have 190-205 psi of cranking pressure (compared to 185-195 when I first built the engine, maybe a little build up in the chambers or a better seal on the rings now).