This is a project from back when we didn't have a fab forum. It's a good example of how easy it is to F up anything cast iron by MIG welding it. be warned. DO NOT MIG WELD CAST IRON UNLESS YOUR A PRO, or else it will have to be repaired over and over again. Hope everyone enjoys this info, i did my best to pass a learning experience on.


Just some pics of me prepping up a Turbo mani to fix some cracks caused by MIG welding cast iron.
Long crack with dimple hole


multiple cracks and someone's Fucked up mig welding trying to hide cracks. not helping the situation.


Another picture where you can see they were trying to cover cracks with some kind of epoxy. maybe JB weld. that kinda smear look at the bottom of the pic


cut channel to try and get the brass down in their.




its been brazed up, will get you some finish pics later.


update pics





its a cast iron manifold. yes you do have to preheat the entire manifold before you begin. the best way to do this is put it in the oven at like 350 or 400 degrees for an hour or so. i have seen people use like propane weed burners, but it has to be a non-carbony gas so that you don't have to reprep the iron when its hot.

While brazing it i just used normal brass fluxed rod. Not the best choice, but the only option i had. One thing that is important is trying to get an nice feathery flame. You do not want an oxygen rich flame. make sure you cut nice trenches in the iron and that you drill small holes at either end of the crack to relieve the pressure of the cracks themselves. The thing that i do like about working with brass is that i am able to go a little heavy with the rod and still clean it up relatively nice.

You also need to insulate the manifold to prolong the cooling process, once you have finished welding. i just used some mulch and dirt and it was hot for several hours. your basic fiberglass insulation from a house will work well also. Several people bury the iron in lime, and it will stay hot for days. sand also works well.

If i could do it again, i would make much deeper trenches for brazing into, and i would have probably made a better effort to remove all of the previous mig weld which was in my way making the manifold look like ****.

I would also have been more liberal with the heat before applying any braze, because once the braze is applied it is hard to reheat the metal without burning the braze.

also, a stainless steel brush helps alot in prepping the surface where you will be welding. as you grind cast iron, you get alot of graphite type material that isn't going to allow for a good weld. just some info in a learning experience to spread to others.

IF i had my choice, i would have tig welded with nickel rod, or oxygen acetalyne welded with nickel. and to all people modding cast iron for turbos or any reason, don't mig weld using normal mild steel wire, it works for a short period of time but then causes massive cracking, as what happened with this manifold. Then people try to fix the cracks with mig, causing even more problems.
Just trying to bring a little something back to life.

 

Brazing temperatures (depending on filler) - 1150°F to 1600°F

EGT's right out of cylinder head (depending on engine/A/F ratio) - 1450°F to 2000°F

Think about that for a minute.

 

I see melting a problem in the near future. Hopefully not, but good luck.

 

i really do not think that the brass would heat up nearly enough to flow. It has been fine to this point, so i can say nothing against brazing cast.

 

you need to find someone that stick welds and get them to use a high nickle content rod, any good welder will know how to weld cast...and yes mig welding on cast doesnt work well...and brazing it is just asking for trouble in the future, for however long it holds up

 

yea i wish i had a tig welder. If i did i would just tig it with nickel myself. I don't know if i like those high nickel stick rods or not. I have seen a few via video over the internet, they seem to work almost like a solder at points, i don't know if i like that or not.