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TR2/3/3A Broken exhaust manifold TR3b

kstanley44

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Hi all,
See attached. Can an exhaust manifold with a broken flange be fixed or is it toast? So far I have not gotten the exhaust pipe off although I haven't tried heat yet.
Thanks,
Kerry 62 TR3b frame off restoration started
 

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TR3driver

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Can be fixed, if you find the right welder/machinist. Lots of work, though, probably not worth the cost. I'd look around for a replacement instead.
 

CJD

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It's toast.

Exhaust manifolds get so hot in use that the metal structure changes. The carbon turns to graphite and makes the metal hard as rock. Welding will not work.

Fortunately, TR3 manifolds are both plentiful and cheap. I think I still have the one from my donor car if you'd like me to check.
 

TFB

Jedi Knight
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Hi all,
See attached. Can an exhaust manifold with a broken flange be fixed or is it toast? So far I have not gotten the exhaust pipe off although I haven't tried heat yet.
Thanks,
Kerry 62 TR3b frame off restoration started

I have welded lots of cast iron,from vintage motorcycle cylinders to coal stove shaker grates,and agree with Randall, not worth the time to grind back to clean metal,build up with weld and machine hole and flange if replacement is available.
Tom
 

martx-5

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Good excuse to install a header...:excitement:
 

CJD

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I'm not saying it can't be welded...I'm saying the weld won't hold. Think of it this way: the manifold gets heat treated every time the engine starts. It amounts to thousands of heat treats, and eventually the grain structure reaches a point that the original grain lattice cannot be recovered with further heat treating.

I've also welded blocks, heads, crankshafts, intakes, you name it. As a young gearhead teen I could not figure out why I could never weld exhaust manifolds with any success. Weld looked beautiful...and cracked. Do it again...cracked again. Later, I studied metallurgy in school, and learned that exhaust manifolds are hardened to the point of no return! The grain structure of the weld can never be matched to the over-treated structure of the manifold, no matter how much you preheat, cool controlled, or otherwise prep the weld. It will end up brittle. A brittle weld may, possibly, last on a grate, but it will never take the load of that stud on the manifold.

Another way to put it...I could weld that for free...and I have saved many a lost part from the grave for no other reason than the challenge of trying it...but I still would not attempt Welding your manifold. It has no chance of success.
 

TFB

Jedi Knight
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Did you ever try nirod electrodes?For example Mg industries makes a MG289 for cast iron.The trick in my opinion is grinding back to clean metal,carefull welding with proper electodes.
 

CJD

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Did you ever try nirod electrodes?For example Mg industries makes a MG289 for cast iron.The trick in my opinion is grinding back to clean metal,carefull welding with proper electodes.

Good (pricey) rods. They would work well on heads and blocks. Have you tried them on an exhaust manifold? It's not the quality of the weld that is the problem...it's the hardening of the old manifold.
 

TFB

Jedi Knight
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Luckily I sourced a supply while employed so cost wasnt a factor.Indian flathead exhaust port nipples get hotter than auto manifolds and I have successfully welded both.
Multiple passes you have to peen the bead to stress relieve.Lowest heat otherwise porosity.My guess is you would get the hang quick.

If you sent me a self addressed envelope I will put a few rods in for you to try or have on the shelf.
 
OP
K

kstanley44

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Thanks all for the metallurgy lesson!!! It sounds like I should be looking for a replacement manifold. John, you mentioned you may have one. Did they change any over the TR3 run? Mime has the following casting number: DA14221 and under that 304164.
Take care,
Kerry
 

TR3driver

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Even TR4 exhaust manifolds are the same. Didn't change until the TR4A was introduced.
 

CJD

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Thanks all for the metallurgy lesson!!! It sounds like I should be looking for a replacement manifold. John, you mentioned you may have one. Did they change any over the TR3 run? Mime has the following casting number: DA14221 and under that 304164.
Take care,
Kerry

Just got back in town...I'll check and PM you...
 
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