I'm fit checking the manifolds prior to installing my Super Six setup and hit a problem not covered in the manifold installation article.

When the intake and exhaust manifold are aligned so the faces are flush to the head and the runners matched to the head ports, there is a serious gap where the manifolds join at the carb heat box. The outer side has a gap of .12 and the inside has a gap of .17. Since the steel gasket only measures .04, it's not going to seal by a long shot.

The odd part is that the manifolds don't appear to have any warping.

If I tighten the manifolds together first, the runners misalign about .125 on one end and the bolt holes in the ends would cause the bolts to ride hard against the manifold ears.

I can have the manifold milled to make up for the .05 difference in parallel, but that means I need a gasket/spacer/gasket somewhere near .17 thick.

Has anyone encountered this much misalignment?...and what did you do?

Does a piece of .125 steel cut to the shape of the gasket, with high-temp sealer on both sides, sound feasible?

I see this all the time, it's a warped exhaust manifold.
Try a different exhaust manifold to see if that helps.
DD

Unfortunately, I don't have another un-cracked manifold and the local wreckers think they are platinum plated, so I really don't want to spend $75 for another manifold that might also be warped.

One word: Header.

$75 is pushing it for a used manifold. New ones from kragen are $130 according to the listing on their site. I believe someone on this board has recently bought one of those.

Cut the manifold into two pieces and the problem is solved.
DD

I talked to a gasket manufacturer today and explained my problem. He said they have a 1/16" thick, white, high-temp material that is used for header gaskets and might work for this application. He knew right off which gasket I was talking about and said since they used to make them, they might even have the original die somewhere in the shop.

I'm going to make a trip to his factory either Friday or Monday and meanwhile he is going to look for the die. If he can cut them, does anyone have any interest in obtaining such a gasket? I imagine it won't cost much more to cut a dozen than it does to cut one. Let me know how many you would want and I will supply them for cost plus shipping. If he can't find the die, we're all out of luck and I'll just hand cut a couple for my own use.

What I would do? Bolt the intake and exhaust together on the bench and surface the head mating surfaces of both manifolds together.

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

It's not quite that easy. Because of the way it's warped, there is also a problem with hole alignment that machining only the flange surfaces will not resolve. You could make it fit by milling both the heat box surface and the flanges, but it would take some trial and error and the labor expense of tying up a milling machine for a custom job would far exceed the price of a gasket.

I had a similar problem when fitting a SuperSix together. The problem turned out to be interference with casting flash on the intakes and exhausts. A couple of minutes with a grinder solved the problem.

I would take a few of the special gaskets if that deal "pans-out'.
Keep us posted.
DD

The guy hadn't found the die by the time I got there. It was one of those really messy places, so I told him not to bother looking any more and I would take some stock to make my own. I selected the asbestos-based material, but he also had metal reinforced, compressed graphite and another that was a metal and graphite sandwich. Cutting either of them would have been more difficult than the asbestos. The stock measured .06 and was the thickest they had.

I just finished making two gaskets and they fit great. It took two layers to compensate for the warp, but I guess we'll see if everything seals okay when I get it running.

The mis-match now looks to be less than .03 and I think gasket compression will accomodate for the rest. If you think that's too much, I might still have the exhaust manifold trued.