I have a cast exhaust manifold that I was playing around with last night. The stock exit dumped right into the steering box of my 57 F100. I put the manifold in my vise and sawzalled the exit off at a slight angle. I then flipped the cut-off piece 180 degrees, chamfered both pieces, and wire welded it back together. I have read alot about welding cast, and I chose to not follow very much of the advice that I have read. Like I said, I was just playing around. I was going to s**** the manifold a couple of years back and just happened to still have it. So here's the question. What kind of failure should I expect? It really does seem to be holding well. I'm thinking when/if I use it, I'll put an extra hanger on the exhaust up towards the manifold in case it breaks off clean when I hit a big bump. OK, let me have it.
It might hold ok.. if you used a high nickel rod it will work better, and if you covered the weld after it was done with some insulation to keep the heat in the weld till it cooled slowly it might even stay forever.. who knows maybe the stars and planets were lined up for you that day and your golden. time will tell
If it does fail, how might it fail? Is it that the weld just doesn't stick very well to cast? Or, is it because of the heat changes, it possibly develops cracks and it might break at the cracks? Or, both?
It won't fail. You welded it. Even if it cracks, just weld up the crack. I split the manifold on my 292, welded it with regular fluxcore wirefeed wire. It's been running now for a couple of years.
it gets wordy.. here is a guide line from lincoln on the subject.. http://www.lincolnelectric.com/knowledge/articles/content/castironpreheat.asp My thought on the failure will be cracks, probably right at the weld where it meets with the cast iron..vibration and impact will be another issue to think about, preheat is a big deal, and letting it cool slowly so i have been taught, so far the welds i have done on some cast parts here at work are still holding up good.
I hear the key is to slow the cooling process down.... I've heard of old timers using those asbestos blankets and wrapping the stuff they were welding. and letting it cool very slow.
My Pop welded it all the time, he welded a lot of furnace grates for the local Amish folks. He'd heat it up on a sand w/charcoal bed, let it get good and hot , weld it with a nickle rod then cover it with sand and uncover it when it was cool.
An old timer I know who has welded many, many heads and blocks showed me how to weld on an exhaust manifold. Unlike a head or block where he preheats the entire thing to some super high temperature and welds thru a hole in his insulation, he merely fired up his biggest O.A. tip and gas welded using cast iron rod. He did tack the two pieces with his stick welder. The big tip not only melted the iron at the joint but preheated most of the manifold.
I "repositioned" the outlet on a chevy manifold once for my 39 Chevy. My buddy was a steamfitter. I cut the angles I needed and he used Brazing rod. Worked very well. 2 Cents.
If it breaks, it will likely break along the side of the weld. Exhaust manifolds are a hit or miss deal, because of all the heating and cooling cycles they go through, the weld may or may not work, regardless of the process used. Add an extra hanger, and give it a shot. Worst that can happen it it will break and fall off, and the heat from the exhaust will toast something. Extra support will keep it from falling off and might reduce the chance of the exhaust heat toasting something. Gene
Hey Gene, I think I bought a beat up old yellow BMX bike from you at a bike show a few years back at the Zettle Bros. shop in Forreston, IL.
A friend of mine welded an exhaust manifold from a 235 Chevy for me. I cut the bottom flange off of the manifold and had it rewelded to change the discharge angle. He slowly heated the manifold, welded it with a high nickel rod and laid it on a wood burning stove in his shop to let it cool down slowly. It's been on my engine for 18 years and about 50k miles with no cracks.
Well, I sold one a few years ago at the Zettle's shop, so you probably bought it from me. Too bad they quit doing that bike show, it was a lot of fun. Gene
Lots of info on this previous post. http://www.jalopyjournal.com/forum/showthread.php?t=182671&highlight=welding
They briefly mention 'spray' welding in that article, not sure if it's the same deal, but a mate of mine showed me a setup for welding cast that he uses... It's a commercially available oxy-acetyline system where the welding head also has a powder bowl and a gravity feed to drop a fine powder into the gas flow.... the idea being that you heat up the area you're welding with the torch and while maintaining the heat, you add this powder to the flame and it slowly builds up the material where you are working... As he said at the time, it's fairly expensive, but when the part you're welding is the last one in existance, or just the last one in the country and it's vital to a high $ job, then it's worth it...
i have welded several manifolds over the years.used ox&ac.lots of heat,br*** rod,lots of flux and along time to cool.never had a problem
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