my buddy has a turbo mani that has a small crack and obviously needs to be welded up.
i was told a couple of things that i needed do, preheat and drill hole at each end of crack (to keep it from runnin away), but i want to know if there was anything else.
i have the cast rods (not sure of the number) and an arch welder

 

Seeming that no one elde has jumped in......................
I have welded cast iron before with mixed results. It isn't so much the rod material that makes cast iron difficult to weld correctly, it is the heat transitions that are mostly important.
~one situation I had to fix a cast iron base for a clothes rack. It was a quick and just get it done job. I welded it with a wire flux MIG set-up, no shield gas. It held (and still holds to this day) but consider that it is not seeing any heat cycles or extream forces.
~on the other end of the spectrum I was asked to repair a cast exhaust manifold. I used a set-up designed more for welding cast iron. We spent alot of time prewarming the entire part to temperature and paying attention to heat control around the weld area. Part cool down was just as importantly watched/controlled. Yes we also drilled the ends of the crack to possibly stop any more crack propagation. Too much though/work...perhaps but this manifold was extreamly rare and difficult to souce a used on in similar shape.

Hope that helps some, I know it can be done. Good luck

 

i heard about this episode on two guys garage and found it...
http://www.twoguysgarage.com/site/preshow.php?PreID=102
according to this you can cold weld it but it requires a 99% nickel rod. sound easy enough and i am all about DIY stuff

 

OK here is how I do it.

Drill the ends of the crack, grid out the crack a bit to make a "V" but keep the bottom of the "V" unground. Preheat with a acetylene torch a bit....I do it by "feel"
Get your TIG ready, with pure argon cover gas with a long pre/post purge, get a high nickel fill rod and go at it. Welds like butter. Allow to gently cool. No sudden shocks, like water or compressed air.

Regards,
BigMoose

Edit to add filler wire specification for those who would like to know what "high nickel means"

This is a good cast iron filler wire for TIG (AWS A5.14 ERNi-1)

Typical Chemical Composition of the filler wire:

Carbon .06
Manganese .30
Silicon .40 (You want 0.4 to 0.5% Si for porosity control)
Iron .10
Sulfur .003
Phosphorus .008
Copper .02
Aluminum .5
Titanium 3.0
Nickel 95.5 (You want a high nickel base)


[Modified by BigMoose, 3:16 PM 8/28/2002]

 

how large of an area...the entire mani or just around the crack
so then you dont recommend using a stick welder w/ a 99% nickel rod?

 

About the size of a softball,more is better, but that will get the job done. Move the flame around, don't stay in just one spot. The trouble is you just get a feel for it. Too cold you have to lay the juice in and it does not flow well. Just right and your off and running.


Didn't say that. I have used stick to repair a cracked backhoe transmission housing and was not happy with it. Others have been successful with stick, but not me. My repair looked pretty, but was not structurally sound. Again for me. Preheat is more critical with stick. I may not have had the preheat right. With TIG you sense its right, you feel its right, 'cause its right.

Good Luck,
Regards,
BigMoose