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mike69 09-07-2009 08:21 PM

Welding exhaust manifolds

I am in the middle of a rebuild of my AMC 390 and I just noticed a crack in one of the bosses where the bolt goes for the exhaust manifold. Does anybody have any advice for welding something like this? I have a MIG welder and O/A torches and I am a reasonably competent welder around the garage, but I have not tried my hand at welding cast yet. I have the Finch welding book and I read the section on welding cast iron...sounds like he recommends preheating it in an oven and then brazing it with the torch. What say ye?


NEW INTERIORS 09-07-2009 08:28 PM

Read this it may help you...

campracing 09-07-2009 08:32 PM

yes you need to preheat the part

you will need to bevel the crack out alittle and then weld it you will need to also weld it in three passes just like welding a main joint one root pass then two filler passes one beside the other

but the most important part is you have to ping the weld (hit it with a chipping hammer or a center punch) all over the weld also LET IT AIR COOL DONT cool it off with anything or it will crack.

when you ping it then just let it sit untill it cools off on its own.

sqzbox 09-07-2009 10:02 PM

I assume your going for an all stock restoration, right? Have you checked the wrecking yards for a replacement manifold? I know the 390 is few and rare but, the 360ci. has the dog leg exhaust manifolds I think are the same as the 390 and are still around. they can be found in 70's AMC's and jeeps made before mopar bought them out. If not a stock resto, I can recommend Doug thorley (I think the spelling is right) long tube/tuned hedders. They are based in LA Cal. I built and raced a 71 Javelin for 2 yrs. and the biggest bang for the buck improvement was the headers I put on. I could really feel the gain in the "seat of the pants" over every other performance part I put on the engine. Any other info you need on the engine just e-mail me and I'll be happy to help! SQZBOX

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