Magnum Heads On 340

[bobscuda67]

Have some cut with a water jet at a good fab shop. I had some small spacers fabed from a gasket for break backing plates.

I have thought about that too. I just wanted to get it running and driving for this summer because I have had a hell of a hard time getting the top of the engine back together after I disassembled last fall.
It would be something I would do in the future for sure.

 

[Swinger 340]

Yes, that's the problem at the bottom of the port with stock replacement magnum heads.
The 340 manifolds are a large LA port and the magnums are a small port head.
I made some 16 gauge block off plates like Dion R made and they leak slightly around both sides of the plate. it's not much around each port but you multiply it times 8, it's annoying.
I talked to a friend of mine tonight and he has a machined straight edge and I'll have him
check my manifold for flatness tomorrow.
The exhaust port on the heads from Hughes are like mine, not enough pad under the port to seal the 340 manifolds. I think the 273/318 manifolds would fit fine, but who wants those on your engine.

Why not use Fel-Pro gaskets and match port the gaskets to fit over the gap and under the exhaust lower port. Should be enough pressor to stop a leak. Never had this issue on a sb Mopar, but I did on a Chevy 350 and had to double up on the gaskets to get a good cushion seal.