In the market for exhaust manifolds for my 72 Cutlass Supreme with a 350. Mine have a corrosion leak at the center port on both sides and need to replace.

 

A machine shop can surface them in many cases.

 

As I understand it, the metal between the ports has rusted away. What do you mean by surfacing them? Forgive the technopeasant question.

 

If they are too far rotted, do you need for single or dual exhaust, in otherwords do you also need the crossover pipe if single? Let me know, I have a 72 I'm parting now

Brett

 

The heads have a depressed area between the ports so they are not separated even with no corrosion, so I don't think you really have an issue.

 

The corrosion is in that depressed area between the ports causing the leak-by.

 

When they resurface them, they put them on a flat sander and basically grind off a little material to make them flat and true. Making them seal well again.

 

Brett,

Need it for dual exhaust, so no crossover pipe. The exhaust guys capped the existing crossover. So, what I'm looking for are manifolds that aren't rotted out at that depressed area between the center ports or linking the center ports -- and aren't otherwise rusted through.

Regards,

Jim

 

That's what I thought you meant. The problem I'm told I've got is the depressed area connecting the center ports has rusted away, resulting in leak-by. But you raise a good point -- for all I know, that may not be the case. It may actually be the need to resurface. I'll do a looksee myself rather than rely on the word of the exhaust guys.

 

Take them to a machine shop and have them checked. It is not much to have a set machined and then they are nice and flat and seal well. There is no such thing as factory small block Olds dual exhaust manifolds. If they had dual exhaust from the factory the one outlet had a block off plate on it factory. The factory big block Olds dual exhaust manifolds will bolt on but do not clear the engine correctly and cause problems. Thornton makes a set of new dual exhaust manifolds but testing has proved no noticeable improvement over the factory manifolds with a block off plate.

 

Understood on the need to block off the crossover pipe -- that was done by the exhaust guys who installed the duals. Don't know whether they blocked off the crossover -- another reason to crawl around and look. And knew the big block manifolds won't work. I've read about the Thorntons needing some field engineering to fit properly.

 

Between which ports? The factory SBO manifold do not have divided center ports, so there is no "metal" there to worry about.

 

if u can't fix them i have a set from a 70 350

 

Figured you would weigh in with the true facts, Joe. I've got to take a close look and not rely on somebody else's word. I'm betting I've got more of a seal/rough surface issue. And I'm almost positive these are stock because everything else is save for the radio and what I now know from Sparky is a remanned 73 QJet off a Vista Cruiser.

 

Here is a picture of a head showing the depressed center divider. Couple that with Joe's picture of the exhaust manifold showing the single opening for the two center exhaust ports and you can see that it would be quite difficult to NOT have leakage between the center ports.

119-1949_IMG.jpg

 

Kenneth,

Many thanks. This is very helpful. Another example of why I've learned to bring an issue to this forum before making a move. I also see why others have said to take them to a machine shop first to resurface.

Regards,

Jim

 

Thanks, luna -- I'll keep that in mind.