Welding Cast Exhaust Manifold

What you do depends on where it is. If you can get a tap into the hole and tread it then a cold as opposed to a welded fill is safer, ie less likely to have distortion or cracking. Welding cast iron needs to be heated slowly to say 350 Deg centigrade then weld then cool slowly. much more effort thyan a cold way of doing it. Any chance of a picture? so we can advise better?

It does have a 1/2" UNF thread in the hole but I want to make sure the plug doesn't come out. I was machining off "Extra" metal to lighten it and found that I had machined off the EGR cast in port. I opened it up and taped it. I can take a picture if it really helps.

David

"Mastic" wrote: (clip) It does have a 1/2" UNF thread in the hole but I want to make sure the

^^^^^^^^^^^^^^^^^^^^ In that case, I suggest, as Ted Frater did, using a threaded plug. You could secure it with tie wire, or else just hit it lightly in a couple of places with nickel arc rod.

Get a 1/2in unf allenscrew and screw that in with exaust muffler repair cement in the threads. This will lock it in once its been run. Wont come out.

Why not just use an ordinary machine screw, grind it almost flush on both ends, and then peen it over a bit? That will lock it for sure and with little hassle.

For that matter you don't need a screw. Just drill a round hole to fit a piece of mild steel rod, and grind and peen that in.

-- Ed Huntress

"Ed Huntress" wrote: (clip) For that matter you don't need a screw. Just drill a round hole to fit a

^^^^^^^^^^^^^^^^^^^ Ed, why go to extra trouble to remove a thread that going to help?

I haven't followed this closely so, if there is a clean thread to begin with, the answer is, you're right, there is no need. Just use an ordinary screw -- the cheaper and softer, the better.

-- Ed Huntress

Yes. Most manifolds are a nickel steel casting. Preheating with a rosebud (or in an oven) and tigging with stainless works pretty well.