View Full Version : Welding Cast Iron

03-30-2007, 05:08 PM
I have an old cast iron turbo manifold that I want to repair. This is really just to get some experience with cast iron arc welding, but it would be great if the manifold could be repaired since it is essentially junk now. I picked up some nickel rod electrodes, but ended up with cracks in the repair (no surprise). I'm going to give it another shot and so I have some questions.

1) In my first attempt I heated the work up with a propane torch till the residual oil started burning off. Would the cold method (weld,ping,repeat) be a good alternative since this is a small area?

2) What is a good method to cut out the cracks in the picture below? I can't fit any cutting wheels in there.


3) The cracks in the first picture might be easier to cut/drill out if they weren't blocked by the wastegate flapper. It looks like I could just grind off the weld in the second picture and pull it out (and weld it back afterwards).


4) Finally, I would like to machine the resulting welds and part of the existing base metal to enlarge the wastegate port. Is it possible to get a "router" bit for cutting metal? I don't have a lathe, but I do have decent drill press. I've looked at alot of local places, but can't find anything like this.

Thanks for any help!

03-30-2007, 05:15 PM
Imposter I say! :D sorry, can't answer your question

03-30-2007, 05:23 PM
I think you have picked a tough job...

To start you MUST buy the correct welding rod.. It Must be machinable type rod. It costs more than regular nickle rod.

If I was to weld this project I would weld until you have a puddle that joins both sides to be welded the stop! Walk away from it until it's completely cool. then knock the slag off and repeat. This method is slow and the joint must be ground out clean before you start and left to cool after each small weld... I have have 99.% success using this method...

The last thing I welded this way was a water cooled merc stern drive manifold to install an O2 sensor for a fuel injection retrofit.

As for how to machine after, your best bet might be a die grinder and a carbide burr.


03-30-2007, 05:32 PM
This is really not a home shop repair , The cracks should be ground out, entire manifold heated to 1600 or so and Cast IRON rod welded. There are a few shops that do this. Not a good application for a Nickle Arc rod repair.... If cracks had not progressed so far, a ring (like a exhaust valve seat) could have been fitted) I have see some repairs done with nickle rod that were impressive but not in that kind of spot. If another manifold can't be found this would best done by pros. As a practice piece too tough.....
To open up wastegate port, an air die grinder with a CARBIDE bit will make short work of that (Wear eye protection) Slow typist got beat.....

03-30-2007, 05:48 PM
Just a comment on welding or brazing cast iron. There is another school of thought, among several;) , that says to preheat then make the repair. As soon as completed place the piece in large container of lime or vermiculite for insulation, cover and let cool until it can be held in your hand without pain, maybe a day or two depending on the mass. While waiting for the cooling cycle to finish a few prayers can be helpful:D

03-30-2007, 07:25 PM
Plain old 7018 welds nearly any cast. Weld it cold, peen it to death every time you stop the arc. I mean peen it to death, like use a cheap air chisel with a dull round point. Adjust the heat to where it doesn't undercut, and let her rip. Did I mention peen it to death?

Mike W
03-30-2007, 08:02 PM
There is some good info here on cast iron welding:

03-30-2007, 09:30 PM
Thanks for all the useful information! I didn't make it to the welding supply before they closed today, so it looks like I won't get to try again till next week. That is a great video. It looks like the key is to prevent large, localized temperature differences. I'll try the carbide burr for grinding out the cracks. I do have a replacement manifold, so its no big deal if the repair doesn't workout.

03-30-2007, 09:33 PM
Braze most of the cast iron that I do.I V out the crack then sand blast it.Heat it to about 450 in a old oven I have in the shop.

Then brase it and put in dry sand to cool......I've done manifolds that have water running throuh them for cooling boat motors....Never had a leak...

Welding a cast iron bearing housing will make the whole srink,Thats the reason I brase most of the cast I do.....Less machining that way..

03-30-2007, 10:31 PM
Done a lot of that even large pieces broken in many small pieces.

Preheat is essential,red heat over the whole part is best.A largish pile of charcoal and a blower will provide the needed heat and 6011 or 7018 weld rod will suffice.Heat the whole thing red,shut off blower and weld it up quick.Heap on more charcoal and turn the blower back on.Before the charcoal burns down completely add some more and cover the whole mess with DRY sand and forget about it until tomorrow.

03-30-2007, 10:42 PM
Is that an IHI turbocharger by chance?

03-31-2007, 11:53 AM
Plain old 7018 welds nearly any cast. Weld it cold, peen it to death every time you stop the arc. I mean peen it to death, like use a cheap air chisel with a dull round point. Adjust the heat to where it doesn't undercut, and let her rip. Did I mention peen it to death?
WELD IT WITH 7018?????? What are you nuts????? You can't do that!!!
Hmmm...or can you?
This is a trick that some pretty crafty old weldors use. On difficult and dirty cast you sometimes can't get the nickle rod to even grab. It'll just ball up in the black sooty mess.
Run a "buttering" pass with 7018 and it'll usually make a good bed for the nickle rod to bite into.
I know and old weldor who is the only weldor in a small town full of loggers and their equipment. He has no formal training in the trade but has welded everthing that's ever broke in that place.
I've seen several of his jobs welding cast...all with 7018. He swears by it and it works. As was mentioned...you do have the peen it.
For the "cold" welding method using any rod...run short beads 1/2" long max. Peen them til they cool, then add another 1/2" bead and so on. Takes awhile but it usually works. If done properly you won't get any cracking beside or in the weld.