When I removed my exhaust manifold on my 69 cutlass 350 (to repair a stud I broke off when removing exhaust pipe) I notice an old crack about 3\4 of an inch long below a bolt hole. It is directed toward the main body of the manifold. I would like to prevent it from cracking any further into the manifold by welding say a half inch bead on the outside of the manifold. Can a pro welder do this on cast iron? Or can welding create more cracking at that site and be worse than I already have?

I've never seen it done, but my welding instructor said welding cast iron is possible, just difficult. A really good welding shop should be able to do it.

JQ

To do it correctly is probably going to cost more than the manifold is worth. Cast iron is not like steel it is not an easy thing to weld.

Various techniques can work to weld cast iron. With a small piece like an exhaust manifold, the person welding it may choose to heat the entire piece before welding it.

You also can cold weld cast iron. Do a google search on "Muggy Weld." They sell special cast iron rod that may work well for you.

If you want it to turn out well, the skill of the welder involved is very important.

It can be done, my father is a welder and I know he's done cast iron before. It takes some skill, but is dooable. If its the original manifold and you need it for that purpose look into having it done.

I have welded a bunch of cast iron.
You never know if the weld will be good or not.
You just take all precautions prior to welding.
Bevel out the crack, pre-heat, weld and pray.
Slow cool it.
Then hope that it does not crack next to the new weld.
The problem is, the weld shrinks when it cools. The cast
shrinks at a different rate. This can cause cracks.
Also, there could be anything from glass(sand) to hunks of 4140 or
ChromeMoly in cast iron. You just never know.
There is a nice AC/DC rod that has a lot of nickel in it that works pretty
well with a good pre-heat.
But its still weld and pray.


I would just look for another manifold.

check out www.z28camaro.com

Jerry does a great job on repairs.

you canNOT weld a used exhaust man. it want last. the cast iron has carbon from the exhaust, which makes the cast manifold not an option for welding.

JB weld

If you must do it. Have it brazed it will work but the process is not cheap.

You can stop the crack from growing by drilling a small hole at each end of the existing crack. The crack can be brazed shut. I've had 2 repaired over the years and they both held up.

I have a brazed one that has been on a car for 10+ years and has held up.

I had an ear crack off a BB exhaust manifold....it was welded back by a certified Aircraft /Airframe welder who has worked with all sorts of "mission critical" airframe repairs. Not saying that aircraft are made of cast iron..my point is this guy knows what he is doing to the point he is trusted to work on helicopters and other such airborne contrivances. The weld has never given me a bit of trouble it even looks good. FWIW if the person who does the work really knows his stuff I think the repair is totally possible.

thanks to all. I have a lead on a very experienced welder who has welded cast gears and other cast parts for a friend. I will let him assess whether he thinks he car repair it. In the meantime I will look for a good used one. If anyone knows where I can find a passenger side exhaust manifold for a 350 Olds engine, circa 1969, please advise.