Cast iron exhaust manifold repair....what to use?

I have a crack on a cast iron exhaust manifold on an older car that I'd like to weld up. It's small enough that once the manifold gets hot, it gets
pretty quiet. I'd like to use flame to do the repair (oxy fuel) so I'm looking for suggestions on what rod to use.
Thanks
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Braze it.

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Take a die grinder and clean up as much of both sides of the crack as possible, then preheat the whole head up to about 500 degF and then braze the crack using oxy acet.
Exhaust manifolds are very difficult to weld because they are so saturated in hydrocarbons, and are usually very thin.
It's almost impossible to get the cracked area clean enough to weld, so brazing is the better solution.
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Welding Instructor - South Seattle Comm. Coll.
- Divers Institute of Technology
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Thanks Ken and Ernie (long time, Ernie!) I assumed something like brazing was the way to go, but didn't know if I needed a special rod. Sounds like standard brazing rod, some flux and I'm good to go. Thanks much, guys.
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On Mon, 22 May 2006 05:06:59 GMT, Ernie Leimkuhler wrote:

I have a cast iron turbo manifold, that is used on a race engine, it glows cherry red 90% of its in use time. It has a small (2 inch) crack that's propagating. Is it a waste of time trying to repair this, if you are brutally honest? I'd like to replace it with a new one, but it's obsolete now. Given an open cheque book, how would you attempt a proper repair? Thanks
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Best Regards,
Chris.
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Brazing is unlikely to be of much value, most brazing fillers will melt at the operating temps you are running at.
First thing I'd check is to verify that the manifold is cast IRON or cast STEEL, different issues. If it is a decent grade of cast steel, any good TIG welder should be able to fix it using a stainless steel filler rod (309??) and decent preheat. If it is cast iron, your only real choice is nickle rods and lots of preheat.
Chris wrote:

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I doubt it is cast iron or steel. More likely it is a nickel alloy. In which case it is quite weldable.
To start try sticking a magnet to it.
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- Divers Institute of Technology
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A few weeks ago I asked for a small Tig machine reccomendation and the Thermal Arch TSW185 was reccomended, this looks almost perfect, as 90% of what I want to do will be thin stainless and aluminum, (< 1/8). I can forsee wanting to be able to a few things in aluminum up to maybe 1/4"
After reading this NG I realize that for 1/4 Al you might need as much as 300A. Is there a machine that will do 250 or 300 A and still offer good fine control at the lowend (5A?) or have I moved into the real of two different machines?
What would someone reccomend for a 250 or 300A inverter machine? How much more is this going to cost?
Paul
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At home I have a thermal arc 300 gtsw it's an older model and has done fine for 6 or 7 years with 220 power it easily puts out 250 amps and welds 1/4" - 3/8" alum. no problem, 1/2" can be done depending on size with lots!! of preheat but it's hard on the machine
at work there is a miller dynasty 300 it's a nicer machine at the low end with better pulser controls than the thermal arc but comes with a bigger price tag, can't compare the top end becouse this machine is plugged into 3 phase (more power in, more power out, better duty cycle) but it does get hotter than mine at home.
thermal arc is smaller and more portable, miller is probably better for warranty and repair service either one you'll want a cooler to do any volume over 200 amps
Dave
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