Exhaust manifold repair

The forum for all of your technical questions on your classic FIAT autos
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engineerted
Posts: 404
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Last Name: Ted
First Name: Russell

Re: Exhaust manifold repair

Post by engineerted » Fri Jan 11, 2019 10:55 am

A few key items that will ensure that you do not develop cracks in you SS header, 1. back purge the inside of the pipe with argon when welding.

A purged weld is flat and tied in on the inside where the weld metal comes together. There are no valleys that could potentially threaten the integrity of the weld. Both portions of the tube look exactly alike.

A non-purged tube displays a “sugaring effect” resulting from the presence of chromium oxide. The presence of oxygen in the weld seam results in oxidation. A noticeable line forms where the weld metal comes together because it doesn’t fuse well. Non-purged stainless steel could crack, especially in high-vibration conditions.

I also use silicon bronze rod on the outside of the header flange, ss rod on the inside. The silicon bronzed does a much better job with the thermal expansions.
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1978 124 steet car
1974 124 EProd race car
Farmington Hills, MI
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bnam2
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Joined: Sat Jan 20, 2018 4:34 am
Last Name: Nambisan
First Name: Byas

Re: Exhaust manifold repair

Post by bnam2 » Fri Jan 11, 2019 10:11 pm

Thanks for the inputs. I’ve passed them on to the builder. They happen to be a leading race team and performance shop. They have won the India touring car championships 3 or 4 times and Joel (the owner) holds the current fastest drag race timing in his category (about 11secs in a 1500cc Honda City). I was connected to them thru a friend who has his cars prepared by them.

Some more pics I got today — merged collector being completed. A flex section is incorporated as the car sits pretty low for indian road conditions which have a lot of speed bumps etc. mufflers also done.
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Byas
1965 Fiat 1500 Cabriolet with 1600twin-cam
!971 VW 1302LS Convertible in original condition
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