filling gap in cast iron

I have replaced a stud in a cast iron exhaust manifold, but as luck would have it, one of the studs that I had to drill out, resulted in a oval hole instead of round. I have replaced the stud, but now want to fill the area around the stud with something that will withstand the heat. I was thinking of melting aluminum or lead around the stud. I don't really want to braze it, as I don't want to heat stress the metal in this area. Any suggestions?? Would brazing heat be too hot for the cast metal? I know it won't melt it..just don't want to cause a crack to form by stressing it in that area. Cold weld stuff won't handle the heat in this area. I guess the running temp in this area will be in the 800 degree range.


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Hi Bruce,

I've never done this, but what about tapping small pieces of brass rod into the area ( providing there is enough room for a small punch) ? I'm assuming the stud is threaded into place and has allot of thread to grab. By doing this cold, you have no heat to worry about.

If you do this let me know if it works.


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Bruce, I'd go with a thread repair kit from these folks or from Helicoil -

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The problem with exhaust manifolds is that they heat up and cool down, many many times, often working loose anything that is not threaded in. Aluminum and lead are too soft and melt at too low a temp, and won't bond anyway. And you're right about the Cold weld stuff. Short of plugwelding the hole and re-drilling it (in cast iron, that's more work than I'd ever do), I think the thread repair is the way to go - you'll get new threads and can use a new stud and that's the last you'll ever have to mess with it. Just make sure you center the drill that drills the larger hole for the insert, and use lots of cutting fluid/oil on the insert tap.

Exhaust manifolds get very, very hot. It is not uncommon for them to be glowing red hot under a load. Most people don't realize that. r/ Steve

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