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Old 11/21/2010, 07:19 PM   #1
Mosesatm
 
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HiPo Exhaust Manifolds

Just a heads-up for anyone thinking of installing reproduction '65-'67 HiPo exhaust manifolds.

Be sure to file or grind down the casting seams on at least numbers 5 and 6, but it may be a good idea to do all of them. The seams prohibit the use of a spark plug socket, which makes installing the plugs somewhat difficult!

I looked it up on-line (afterwards) and found out it's a common problem.
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Last edited by Mosesatm; 11/21/2010 at 08:41 PM..
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Old 11/21/2010, 08:04 PM   #2
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The webbing between the runners? Good to know. Thanks Arlie.

Scott Behncke
1968 GT/CS 302-4V Honors flysis income beezis onches nobis inob keesis
West Coast Classic Cougar A good source for Mustang mechanical parts too.
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Old 11/25/2010, 12:29 AM   #3
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Interesting... My son was just given a mint set of original HiPos. Cast C7ZE-9430-A and C7ZE-9431-B, we put them on yesterday and had no issues with sockets...

Tim
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Old 11/25/2010, 07:12 AM   #4
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Quote:
Originally Posted by Midnight Special View Post
Interesting... My son was just given a mint set of original HiPos. Cast C7ZE-9430-A and C7ZE-9431-B, we put them on yesterday and had no issues with sockets...
There are no problems with the originals, just the repos.
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Old 12/31/2010, 09:15 AM   #5
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And there are even more problems with the reproduction HiPo exhaust manifolds!

I decided today was a good day to find and fix the passenger-side exhaust leak that recently cropped up in my new exhaust system. What I found is upsetting to say the least (especially in light of the recent lower control arm issue).

It looks like the bolt holes where the exhaust manifold bolts onto the head are drilled in the wrong place!!!! The holes should be just above the centerline of the port but on the passenger manifold they are drilled just below the centerline.

I went on-line to see if I some Mustang resoration god has placed a curse on me or if others have experienced the same problem and looky what I found!
http://forums.vintage-mustang.com/co...-manifold.html

If MU doesn't replace the manifold I guess my only options are to weld up the holes and redrill them, or spend $500 on a set of OEM Hipo manifolds.
Another option would be to leave the holes alone, grind out the excess material on the ports, and install the manifold without a gasket, increasing the mating surface between the head and the manifold around the port.
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Old 12/31/2010, 10:10 AM   #6
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I would go with option "C". 1969 351W exhaust manifolds for a Mustang or Cougar. Very similar casting to those HiPo manifolds.

Ford never used gaskets on cast iron exhaust manifolds from the factory.

Scott Behncke
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Old 12/31/2010, 12:30 PM   #7
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New development.

I measured the #1 exhaust port as best I could and found that the centerline of the bolt holes seem to more or less line up with the center of the port so the holes are still wrong in the manifold but they are not as wrong as I first though. In fact, I think I can resolve the problem by just going gasketless as Scott mentioned.

What I also found by measuring the port is that the openings on the manifold are 1 1/2" tall but the matching ports on the head are only 1 1/8" tall (HiPos must have had ported heads?) and the entire difference (3/8") is in the top of the openings. So instead of enlarging the opening by extra 3/16" on both the top and the bottom they took it all out of the top, and that may work for a HiPo but it doesn't work for a stock '66 head. The bottoms of the openings line up fairly well, but the tops are way off and using a gasket creates a common mating surface of less than 1/8" at the top. Instant exhaust leak.

Hopefully some copper RTV on both surfaces will be enough to make a good seal, but before I do anything the manifold is going to a machine shop to make sure it's perfectly flat. For some reason I have a hunch it probably isn't.

Last edited by Mosesatm; 12/31/2010 at 01:27 PM..
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Old 12/31/2010, 01:07 PM   #8
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Long ago on a different forum, an oldtimer stated a possible reason Ford didn't use exhaust gaskets. Direct mating of the two surfaces, work as a heat sink, and helps dissipate heat away from the engine.

Arlie, I wouldn't be concerned with having slightly larger exhaust ports on the exhaust manifolds. Smaller would be a problem.

Scott Behncke
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West Coast Classic Cougar A good source for Mustang mechanical parts too.
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Old 01/02/2011, 07:38 AM   #9
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That's right by using the gasket the manifold temp is much hotter resulting in warped and broken manifolds. The MCA deducts for the use of gaskets. I machine mine then paint the engine surfaces with the engine paint and the manifold surfaces with the manifold paint and use antiseize on the studs and torque them. Run the engine for a hour and retorque them after it cools. I have never had one leak. Marty

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Old 01/05/2011, 07:36 PM   #10
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Wonderful advice Marty. It worked great!
Of course painting the exhaust ports with the engine in the car was a bit of an adventure!!!
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