[custommetal2001]

I am trying to weld up an exhaust manifold off of a Bobcat. I have cleaned it and grooved it, I have tried to arc with nickle rod, TIG it and just straight Mig it. Every process acts like Im welding steel with the gas turned off. I have welded a cast manifold completely back together before. But this has me baffled. Any one have an idea what may be wrong?

[smithdoor]

I am trying to weld up an exhaust manifold off of a Bobcat. I have cleaned it and grooved it, I have tried to arc with nickle rod, TIG it and just straight Mig it. Every process acts like Im welding steel with the gas turned off. I have welded a cast manifold completely back together before. But this has me baffled. Any one have an idea what may be wrong?

Per heat to about 500°F or more
Use Brazing , cast iron or nickel cast iron rod

Dave

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[smithdoor]

I am trying to weld up an exhaust manifold off of a Bobcat. I have cleaned it and grooved it, I have tried to arc with nickle rod, TIG it and just straight Mig it. Every process acts like Im welding steel with the gas turned off. I have welded a cast manifold completely back together before. But this has me baffled. Any one have an idea what may be wrong?

Per heat to about 500°F or more
Use Brazing , cast iron or nickel cast iron rod

Dave

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PS let cool very slowly (24 hours)
Cover with at least 6"of verniclite found at Home Depot , Lowes or any gardening store

I use brazing rod and torch

Dave

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[Poland308]

Could be a real bad quality casting with lots of porosity internally, before you even light up on it. Or it might be saturated with oil residue from the exhaust. If it’s oil contamination then the preheat should help some.

[custommetal2001]

I did preheat to 500 + deg. I have nickle rod, I have silicon bronze filler, I tried to mig it just to see. Every process acts like I'm wire welding without any gas.
The nickle rod just balls up, some spots it will just knock off with chipping hammer.
I have welded cast iron, many times. had a guy cut the flange off to re clock for a turbo, welded it with nickle rod. preheated and slowly cooled it down.
This has me puzzled.

[custommetal2001]

Could be a real bad quality casting with lots of porosity internally, before you even light up on it. Or it might be saturated with oil residue from the exhaust. If it’s oil contamination then the preheat should help some.

This makes sense!

[Poland308]

If you tig weld over top of a mig weld it will act like you have no gas.

[motox]

try grinding a nice clean V, heat the weld area cherry red to clean out the oil.
set the torch slightly carbonizing before you braze.
craig

[motox]

a couple passes with a clean file also helps.

[kiwi2wheels]

try grinding a nice clean V, heat the weld area cherry red to clean out the oil.
set the torch slightly carbonizing before you braze.
craig

Years ago in NZ, there was a flux that was used to tin the edges of cast iron before using the standard CI bronze flux. It was labeled as " Unity Flux ".

I wonder if such a product is still available from specialty O/A rod and flux suppliers.

It worked well, my O/A course teacher used it to build up a broken spoke flange on my Triumph front hub.

[motox]

Years ago in NZ, there was a flux that was used to tin the edges of cast iron before using the standard CI bronze flux. It was labeled as " Unity Flux ".

I wonder if such a product is still available from specialty O/A rod and flux suppliers.

i think here its called Oxweld or something like that

[Coldman]

If you’re going to braze it, a trick that worked for me in the past on dirty/bad castings is to rub the casting surface with the end of a copper pipe or bar until you can notice a rosy sheen to the surface. Braze normally, the filler takes.


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[Antorcha]

500F isn't enough preheat for something that dirty. Take it 800 plus and let it schmoke for a good while ! Clean it up inside and out and do it again this time putting the braze to it and put it back in a heat source to slow cool a few-several hours.On a hot summer day running hard and bouncing all over the place that manifold can reach 1000 degrees.

[Mike Westbrook]

If that bobcat has a Ford engine in it (the older ones had English escort engines ) I've had huge trouble welding some Ford manifolds seems like the ones that are kinda clay colored it's some weird junk aloy I never figured those out either lots of preheat and mig wide cursive g's like 3/4 an inch is the best luck I've had and like others said bed it in sand or vermiculite to cool slowly good luck

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