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Hi guys, happy new year it’s been a while since I’ve asked questions or posted anything. I always try login and read the topics though.
So I’ve been wanting for a while now to change the exhaust on Big Red like the whole exhaust. I’ve gone back and fourth on yes or no it’s been a two year thing and finally I’ve decided I’m gonna do it. Now I have the efi manifolds but I’ve decided to go back with my hedman header. Now back when I had it I remember that it blew out a gasket and I was wondering if I cut the header on the flange and make it a two piece deal. Would this cure this problem?
the yellow mark indicating where I would make the cut
I will also be sending out the header to get ceramic coated.
Hedman seems to make pretty good stuff (and they're affordable). The issue is most likely that the header tubes expand at different rates (distorting the mounting flange) which is why the gasket ends up leaking. I think I would try to make the gasket meeting surfaces, on the header, as flat as possible (kinda like milling a head but done with a big flat file). IIRC, that hole in the middle, by your yellow line, is for a locating pin, not a bolt, right? If so, I might cut directly thru the flange at that hole.
Another thing you could try is to make sure that the intake manifold tabs and the exhaust header flange are the same thickness so that the mounting studs/washers/nuts (that go into the head) are applying equal pressure to both the intake manifold and header.
If you think you might want to sell those EFI manifolds, please keep me in mind (you're not far from me).
Hedman seems to make pretty good stuff (and they're affordable). The issue is most likely that the header tubes expand at different rates (distorting the mounting flange) which is why the gasket ends up leaking. I think I would try to make the gasket meeting surfaces, on the header, as flat as possible (kinda like milling a head but done with a big flat file). IIRC, that hole in the middle, by your yellow line, is for a locating pin, not a bolt, right? If so, I might cut directly thru the flange at that hole.
Another thing you could try is to make sure that the intake manifold tabs and the exhaust header flange are the same thickness so that the mounting studs/washers/nuts (that go into the head) are applying equal pressure to both the intake manifold and header.
If you think you might want to sell those EFI manifolds, please keep me in mind (you're not far from me).
yes I noticed when I flipped the header to see the exhaust ports they weren’t flat at all. I probably have to take the grinder to them to see if I could do any good to them.
yes I noticed when I flipped the header to see the exhaust ports they weren’t flat at all. I probably have to take the grinder to them to see if I could do any good to them.
I did this once or twice for V8 (289 & 460) engines. The hardest part is finding a way to secure the header without damaging the tubes yet still having complete access to the flange. I don't think you'll want to use a grinder because it won't span multiple exhaust port openings (and could be a little too aggressive). Use a straight edge and a long flat file. You should be able to start at one end and work your way towards the other doing 2 or 3 openings at a time. As you progress, check your work with the straight edge. If you can find a straight edge that spans the entire header, that would be ideal. You want all six openings to be in the same plane (or as close as possible).
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