What tips can you guys give me for tig welding cracks in my 235 exhaust log. I have ordered up some nickel rod (55/25) and plan to "V" the affected areas. Am I on the right path? Thanks, Dave
I'm no expert and there are probably a ton of better welders on here than me, but that sounds about right. Thats how I fill cracks. V'ing them gets you better penetration and they will hold up longer. As far as what rod to use, my best guess won't come close to your worst one.
I have found that when tig welding cast iron if you set the power supply on A/C you will not get near as many blow outs as you do with D/C. I know it sounds weird, I friend of mine found this out when he forgot to change the power supply settings from his last task which was aluminum. When he told me about it I thought he had lost his mind, but I tried it anyway and it worked great. I have been welding cast iron with this method for over 10 years without a single failure. I have even gone as far as sawing off part of a engine that had bad internals and welding onto an engine that had good internals but had crash damage. I did this type of work for a junk yard for years and it always worked. With cast iron the best plan is to work slowly and not overheat the metal. Also, when welding a crack drill each end of the crack with a 1/8th inch drill bit and it will keep the crack from growing as you apply the heat. Exhaust manifolds can be tricky because the metal has been through countless heat cycles.
Hey, If ya can, unbolt the manifold and bolt some angle iron or plate to each of the runner flanges. Grind, drill holes as suggested at the ends of cracks, pre heat with a rose bud,weld in small patches, "normalise" the metal with a chipping hammer, weld in small stiches when welding is completed, post heat, again with rose bud, than I'd bury it in a box or pile of VERY dry sand. Allow it to cool overnight. Swankey Devils C.C.
ive had excellent luck welding manifolds and other ci parts with just a mig welder. nothing fancy just preheat and cool slow. sounds crude and low teck but it works fine....
that tig rod is freaking expensive. i bought some to fix a head a coupe weeks ago. its a little tricky, you need to get it nice and hot almost a dull red when you preheat, when you V it, dont go all the way to the bottom of the crack, that rod really sinks in. i never tried it on a/c but it did cross my mind. you want it nice and clean too.
Thanks for all the replies, I ordered 1lb. of the rod and it is costing $23.90, so be it. I hope to save this manifold, not quite ready to invest in headers & new pipes. I am going to look around for a practice piece, I am curious to try AC vs. DC. Thanks, Dave
I had a small engine that threw a rod out the block, i took it to a guy that tried to use a nickle rod to fix it after several attemps he gave up. I took it home and brazed it together, it is still running and that was fifteen years ago. I second the brazing method for cast iron. Don't know if it applies to a cast iron manifold but I wouldn't hesitate to try it.
I recently aquired a exhaust manifold for my 51 that had the split dump brazed on......it lasted about a week. When I got it off, the "break" was right at the braze, it looked like it was glued on, no penitration what so ever. I re-did it with a stick welder and cast rod.....been holding ever since.
I AC stick welded my daughters Geo cast iron manifold (cracked all the way around)with the nickel rod. Glass beaded it first and v grooved the crack. Had the ox/acetyline torch in one hand preheating (cutting tip), with the stick in the other hand. Kept the heat on after the weld and slowly decreased the heat. Wrapped it in a welding blanket for a slow cool. This process worked great. A young engineer said it would never work - but I've met many young engineers that don't know how to use tools.
I also have had real good luck with a mig. I welded a small block chev manifold and couldnt believe how nice it welded.
If you can find somebody that has a needle scaler, they work well for peening the weld as you proceed. It helps to relieve the stress in the weld
The trick I've heard, is fire up the BBQ, and use it to pre-heat, and post-heat the part... big thing is getting it all up to temp so that it doesn't crack as it cools.
I used the aceteylene torch method to braze the seams on an old wood stove, (type with two burners on top) it made the stove virtually air tight and it would hold a fire overnight. So brazing is a good way to get a seal when the metal is reheated from the exhaust. it just isn't as pretty as a mig weld.
brazing is not meant to penetrate the material it is a disimilar metal and that basically will happen from heat cycling. that same can happen with a ni-rod weld. if itsa super odd piece, i can hook you up with aguy in maryland that is a cast iron specialist, he gas weld cast iron with cast iron, his prices are great too. i am a certified welder an di recently sent some stuff to him to be repaired, it simply was not worth my time and effort to repair a piece of cast iron the wrong way, it was a part that i could not afford to screw up. th ebbq method works to get th epart heated evenly but you should still get the heat up even higher where you have to weld, throw it in the bbq when you are done welding.
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