Manifold Repair 101

Q: Manifold Repair 101

I welded it up but the weld makes it not seat properly (I tried to grind it but I went through 2 grinding stones on my drmmel tool and barely made a dent) so it’s leaking pretty bad.

A: You’re a brave soul welding a cast iron manifold while still on the car. Its quite tricky welding cast iron so as not to have it crack again. Ive successfully welded quite a few exhaust manifolds never to have one crack (even 25yrs later) but its a real science. I had an old timer show me(guess Im qualified to be in that category myself now)

First is to drill on the extreme ends of crack to stop it from continuing. next grind a good size V into crack but not all the way thru. Preheat the cast iron in repair area until cherry red with a rosebud tip. Keep the torch moving or youll blow out a hole in the cast iron. while still red then use a high nickel rod and use less heat (amperage) than you normally would(remember youve already got it hot).

After welding is done work very quickly before it cools and peen it with the pointed end of a welder hammer all over the weld. Next place in a bucket of clean dry sand and completely cover with at least 6 inches of sand .Leave there overnight as you want it to cool very slowly. You can preheat in an oven and cool down in an oven gradually bringing down the temp over a 24 hr or longer period as the pros do.But just remember to take it out before the pizza goes in. Now as Tim Allen says I think Ill go break something so I can fix it.

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