welding a cast iron exhaust manifold

[bwtrout]

i have two hair-line cracks on the bottom edge of the exhaust manifold. it's a stern drive 76' 120 mercruiser. any leads on a welder that would work with cast iron?

[Diezel350]

I ran into the same problem a few years back with a ford 302 manifold. From what I know cast iron can't be welded, but I don't weld so I may be wrong.
I ended up finding a manifold at a salvage yard that lasted for a little while but again cracked a couple of years down the line. I finally ended up getting aftermarket shorty headers, actually lower cost than the stock cast iron manifold and didn't crack.

[Gissert]

Cast iron can be welded, but it must be preheated. Not your normal welding process. If you can get the manifold off, a good blacksmith should be able to weld it for you.

On something like an exhaust manifold, you are better off going new, or finding a used one that is not cracked.

Sometimes JB weld will work for a while on small cracks. It is an inexpensive fix to try at least.

[Valv]

Bwtrout, I will look into it, I have here a old manifold for a Mercruiser 4 cylinders.
These are the kind where intake and exhaust are together, if this is what you have, just make me an offer.
I will be able to bring it to Glenwood City, since a friend of mine just moved there and I see him very often.

[Eric Wettschreck]

I weld pretty much all the time, every day (unfortunately). I agree with RM20, cast can be welded, but it isn't recommended as a permantent fix. Preheat it good, weld it with stainless rod, and let it cool down slow. Some people even run a torch over it with a quick pass right after they are done welding. This helps the slow cool down. My advice, get a new one.

[Surface Tension]

Valvs got just about everything, I wish you lived next door.
bw after going through the hassle of removing the manifold your not going to what a patch job. Hopefully Valv has what you need.

[bwtrout]

thanks for all the info!
valv, i'm very interested in picking up a used one. my email is: [email protected]
i just moved to duluth.
boilerguy, i'm burning coal as i type.

[rmh2o]

You can either braze cast iron or weld it with stainless steel rod but the problem is it will weaken the metal and probably crack again next to the weld.Preheating and slow cooling helps but tends to be a temporary fix.I suggest you look for a new or used one.

[Gus]

rmh20 is correct by my experience. When I had one done it just re-cracked and re-cracked until I picked one up for $30 at a junkyard. Of course this was for a car and not a boat, but I'd look for a used one rather than waste time trying to fix the old one. You'll probably have to fix it agan anyway.