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MGB Which exhaust mainfold?

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kennypinkerton

kennypinkerton

Yoda
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I just bought a nice restored HIF4 setup on ebay... I know exhaust manifolds changed over the years, which one will I need to go with this setup?
 
You'll need one to fit a '72-'74.
 
Will the 12Hxxxx number on them tell me which ones I'm looking at? I see many on ebay, 12H709, 12H3911, etc, where the date either isn't listed, or the seller says 1962-80, lol.
 
I believe the one you want is the 12H3911. Will have to double check that.
 
I've been searching (off and on) all day... where would I find that exact info? It's not in any of my catalogs. I feel kind of silly that somehow I have limited myself to something only made for 3 years. My luck, lol. I hope hif4 carbs were the way to go over hs4. I guess anything would be better than the restrictive (and incomplete) zs setup I have now.
 
go with a header, better flow and easier to find.
 
They probably are, but steel rusts, SS is expensive, and I can get a cast iron manifold for about $100 shipped to me that still flows 100 times better than the abomination of a manifold that was on the 77.
 
JPSmit said:
go with a header, better flow and easier to find.
Click to expand...

According to most, the factory manifold is actually as good as it gets. Keeps heat down in the engine bay and is quieter. Also, less chance of rust-through. And cheaper. They pop up on ebay fairly often.

Here's one; needs studs, but they all do: https://www.ebay.com/itm/Very-Good-...ash=item465d7482e8:g:CDUAAOSwNsdXRfEx&vxp=mtr

'nother one: https://www.ebay.com/itm/MG-MGB-EXH...ash=item1a23be089b:g:a5oAAOSw2xRYehR7&vxp=mtr
 
kennypinkerton said:
I've been searching (off and on) all day... where would I find that exact info? It's not in any of my catalogs.
Click to expand...

The 12H3911 is what came on my '73, and when the header I put on it when I rebuilt it dies, it's going back on. :wink:
 
Only thing you can do to a B manifold to make it a little better, is to polish the inside and ceramic coat it. The original manufacture did a wonderful job on the design, it's as near perfect as it gets and the only reason to abandon the original manifold is weight, as in racing, every ounce counts. PJ
 
You can use either exhaust manifold. Just make spacers to make up the difference in thickness. Quick easy way is to cut a couple of thick washers in half...or stack thinner washers if needed. Superglue will hold them together while installing them Once the nuts are tight they won't go anywhere...
 
Thanks guys.
 
image.jpgKenny,
beadblasted and checked for cracks.
Marv
 
Kenny,
Marvs manifold looks great, but if it doesn't work out try Michael Powell at Bell Auto in Northport, AL.
Rut
 
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