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Old 04-13-2016, 02:36 PM   #1
Don/WI
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Default Manifold machining

I recently attempted to machine a manifold assembly. I mounted the assembly using the carburetor mounting to fasten it to an angle plate on my milling machine. In doing so I noticed that the manifold mounting surface is not perpendicular to the carburetor surface. I measure approximately 0.024" difference from one side to the other on the 2" width. Does anyone know if there is an angle at which the manifold should be mounted when machining or will machining them perpendicular to the carburetor cause any problem? I would appreciate any information that I receive. Thanks. Don/WI
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Old 04-13-2016, 02:43 PM   #2
Mark in MT
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Default Re: Manifold machining

The engine crankshaft center line is engineered at a 3 degree angle down towards the back of the car. When installed the carb hangs level, so the mounting flange of the intake manifold is machined off at a 3 degree angle also. You may try to use the center 2 ports of the exhaust manifold as your datum to set it in level, this part of the manifold is thick and square, least likely to warp as compared to the ends.
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Old 04-13-2016, 03:14 PM   #3
Don/WI
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Default Re: Manifold machining

Quote:
Originally Posted by Mark in MT View Post
The engine crankshaft center line is engineered at a 3 degree angle down towards the back of the car. When installed the carb hangs level, so the mounting flange of the intake manifold is machined off at a 3 degree angle also. You may try to use the center 2 ports of the exhaust manifold as your datum to set it in level, this part of the manifold is thick and square, least likely to warp as compared to the ends.
Mark, I do not mean that angle. I'm wanting to know if there is any angle other than 90 degrees between the mounting surface of the carburetor and the 2" width of the manifold mounting. Thanks for your reply anyway and I agree with your statement. Don/WI
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Old 04-13-2016, 05:22 PM   #4
Bob C
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Default Re: Manifold machining

Here is a small picture someone posted of a fixture.

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Old 04-13-2016, 11:17 PM   #5
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Default Re: Manifold machining

best method for those is to surface grind I doubt youll be able to hold it rigidly enough to machine it...
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Old 04-14-2016, 04:43 AM   #6
BRENT in 10-uh-C
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Default Re: Manifold machining

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best method for those is to surface grind I doubt youll be able to hold it rigidly enough to machine it...
To a degree, I agree with you however you are in the same circumstances fixturing for a SG. I use a flycutter with a very light cut on each pass. I don't get chatter that way but it is SLOW. I have also learned that HSS doesn't like rust.
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Old 04-14-2016, 06:04 AM   #7
Kurt in NJ
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Default Re: Manifold machining

I have a Van Norman 561, it came with lead fingers for fixturing exhaust manifolds-----
The last manifold I used a belt sander and a file because I was home and that is what I had to use there, perhaps a bit slow, but it doesn't leak

I have fixtured similar shapes in a bed of bondo---wrap the part in shrink wrap and settle it into a large gob of bondo
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Old 04-14-2016, 06:53 AM   #8
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Default Re: Manifold machining

I use a belt sander. It works fine. Be sure to wear a mask, as the dust is bad for the throat.
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Old 04-14-2016, 07:03 AM   #9
Terry, NJ
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Default Re: Manifold machining

My guy, Majewski Machine, Trenton, NJ, uses a blanchard. The Blanchard uses a large array of segmented stones and a large magnetic rotating table. It leaves circular grinding marks from the stones. But I think the original posting dealt with whether or not the carburetor mounting surface was exactly 90 deg. to the block surface. I have not seen or heard of a anything but a 90 deg. relationship between the two.
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Old 04-14-2016, 10:25 AM   #10
Don/WI
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Default Re: Manifold machining

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Originally Posted by Terry, NJ View Post
My guy, Majewski Machine, Trenton, NJ, uses a blanchard. The Blanchard uses a large array of segmented stones and a large magnetic rotating table. It leaves circular grinding marks from the stones. But I think the original posting dealt with whether or not the carburetor mounting surface was exactly 90 deg. to the block surface. I have not seen or heard of a anything but a 90 deg. relationship between the two.
Terry
Thanks Terry. I did some searching and ended up with a few other Barners that said the same thing with no one posting a different angle. The one I was going to machine must have been warped. I will machine it at 90 degrees.

Thanks also for all the replies. I learned a few things. Don/WI
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