Anyone know of a header that will seal well up against magnum exhaust ports? The Dynomax headers I had sealed fine up to an LA head (plenty of contact to machined area all the way around ex port) but the magnum exhaust port is raised and the bottom of the header flange opening barely overlaps the lower machined surface of a magnum head (under the exhaust port opening).

Nothing off the shelf, I usually weld up the dog leg area of the flange and grind it flat, even some of the headers for late model trucks use the LA flange.

I usually weld up the bottom 1/4-3/8" then lay a Mr Gasket magnum gasket over the flange and mark what needs to be removed with a sharpie, crude but it works.

summit long tube headers (I think they're flowtechs) seal up fine on my mag heads using copper RTV on the gaskets.

My thinking is if the header flange seals fine on a magnum head, it may cover some of the lower part of the ports on an X or J head.

I have hooker 1 5/8 competion headers on my magnum heads no problems here.

That's the trick !!

Dan

you are not imagining this problem! There is only about 3/16" common area comparing the bottom of the LA port to the bottom of the Magnum port.

you're looking at an LA gasket crushed against a Magnum port.

I made sheet metal adapters, outside dimensions of the LA port, and inside dimensions of the Magnum port. Sandwiched the adapters against the magnum port with LA gaskets between the adapter and the manifold (or header). These adapters along with a Remflex gasket solved my leaks.

Some report a hump on the Mag heads that stops the manifold from sitting flat, I did not see that in my case. The Remflex gaskets are good enough that they may still seal without the adapter plates.