Welding castiron exhaust manifold

[System-f]

There is a crack in my mainfold and I would like to weld it.
These are the steps I have gotten so far.

1. Clean/grind area to be welded
2. Pre-heat, with propane torch, or running on the engine????
3. Weld crack, what nickel rod?, what current setting for assuming 1/8" thickness and 2/32 or 1/8 rod?
4. Peen weld with peening hammer?
5. post heat weld...
6. let slow cool



Is this right? If I can reach the area does anyone see a problem with welding this while it is on the engine?

[weld_slag]

Originally posted by System-f
There is a crack in my mainfold and I would like to weld it.
These are the steps I have gotten so far.

1. Clean/grind area to be welded
2. Pre-heat, with propane torch, or running on the engine????
3. Weld crack, what nickel rod?, what current setting for assuming 1/8" thickness and 2/32 or 1/8 rod?
4. Peen weld with peening hammer?
5. post heat weld...
6. let slow cool



Is this right? If I can reach the area does anyone see a problem with welding this while it is on the engine?

1. Yes, remove ALL grease and oil
2. Not real critical but you may want to warm it up a bit. Do not over heat though....very bad for cast iron. Preheat should not exceed 200 degrees.
3. I would use a nickel electrode like Lincoln Softweld 99 3/32" 50-80 amps
4. Sure won't hurt
5. Not neccessary.
6. I would allow it to slow cool though. Maybe cover it with a canvas tarp or something like.

other things that may help.
1. If the welds are long say like 7" or longer it may help to drill small holes every 3" or so to aid in stress relief.
2. run stringer beads, not weave.
3. do not run long welds, keep them short and be carefull not to put too much heat input (interpass temp). Try not to exceed 400 degrees

I'm sure I'm forgetting something or maybe this may be over kill but I have no idea how long the crack is......does make a difference how to approach welding it.

[Portable Welder]

This method is for a off the car application,
I like to braze all my manifold jobs unless its still on the car then I use a nickle rod.
For brazing, I grind all the scale back, vee-groove it and while vee grooving I like to put little serations down in the vee in a chris cross pattern. I then pre heat the bench I'm working on and then the manifold,I like to get it about the same temputure that it is when its on the car, I dont have fancy equipment to test how hot it is I use my cheek, gloing red is way to hot, I then braze it and peen it between passes by putting a point on my chipping hammer, alot of light taps, I then pre heat again depending on the size of the crack, and then do a finish pass if it needed it, then post heat it, peen it and put a card board box over it.
I'm not sure how good my method is but I've never had any come back so I can only assume it worked, and I've done at least 30 or more over the years.
Note: When repairing cracked ears on engine blocks I arc weld with nickle rod.
I always tell my customers that its cheaper to get a used manifold at the junk yard than for me to repair so I usually only repair hard to find manifolds. Good luck.

[Mike Sherman]

There are two effective procedures for welding cast iron, both have been discussed many times on this board. The procedure given by weld slag is often referred to as cold welding. It will work, keep the temp. down below 200 F., use short stringer beads, peen, let cool to the touch between welds. The other is hot welding, which I prefer. Heat cast to between 500 and 900 deg. F, maintain this during welding, use stringer beads, weld out completely with a cast iron electrode, cool slowly, wrapped in a welding blanket or sand or vermiculite. Let it cool atleast overnite. Brazing is also effective when done right.

[customwelds]

I would hesitate to weld it on the car. I'm not an expert in anything but I'd have to wonder about putting current through a motor with so many electrical guages and hook ups and etc etc...Also there's the chance of blowing something up in there...oil, gas, grease...etc...Again I've never tryed it and don't plan to but I guess it could be possible to weld it on the car...