Guest zthang43 Posted March 23, 2002 Share Posted March 23, 2002 Does anyone know much about welding cast iron? I've heard you aren't supposed to, but I've done it once on an exhaust manifold (cut and welded it for clearance) with no problems. I'm thinking about just welding up a crack in my turbo, and a section that got burned away as well. Does anyone know if this will hold up, or will it just crack and burn away again fairly quickly? The reason I ask is a decent used CT20 turbo is hard to find and expensive. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 24, 2002 Share Posted March 24, 2002 There was another recent post on welding cast iron manifolds with various solutions.I would suggest that if you had sucess with welding other cast iron material with special rod and heat preparation , then try it. Your other alternatives is to find the secret proceedure which I do not have a clue but someone else may,a professional who will take joint custody of your wallet,find a used unit. Hang in there and repost if your answers do not appear right away. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 24, 2002 Share Posted March 24, 2002 I read a article a while back about repairing cast iron. They had a kit somewhere that sprayed powedered metal into the cast part. All it used was a propane torch and a lot of time. They preheated the part to somewhere around 400degrees and then put the filler metal in then cooled it down very very slowly. if you cool it fast it will crack. To cool it slow they just took the torch back a couple of inches every so often. I wish I could find the article. i know it was in a car craft just don't know the date off hand. it worked on the head they ported a little too far. I don't know about using a arc or anything. maybe taking it to a shop that does welding alot will help best of luck Quote Link to comment Share on other sites More sharing options...
johnc Posted March 25, 2002 Share Posted March 25, 2002 The part needs to perfectly clean, bead blasting is preferred. Grind the crack into a V notch so there's room for the weld and the filler. Preheat the entire part to at least 400 degrees and keep it hot the entire time you're welding. Use a stick welder and a high nickel rod. Weld in short (1 to 2") passes and alternate from each end of the crack. Cool the part down slowly, maybe over a 30 minute time period. But, since you're welding a turbo hosing that will go through some sever temperature swings, I don't think there's much chance this repair will last. Quote Link to comment Share on other sites More sharing options...
Supra510 Posted March 26, 2002 Share Posted March 26, 2002 Not that any of this is gospel, just my experience. I have used this on 2 turbine housings and both a Toyota Supra exhaust manifold and a 280zx Turbo manifold. I ground off the rust (very important) and MIG welded with regular mild steel wire. I contacted a welding shop and there is a special wire to use with cast iron but it is very expensive. They said that if the steel wire works, well for lack of better words, it works. I have welded on a steel flange to both mainfolds and a steel wastegate inlet to 2 different turbine housings with no problems or cracking of any kind--The manifolds were at room temp. I have daily driven the car for over 10k miles, driven throught the Nevada desert with 120+ temps and had the car at Thunderhill Raceway with 104+ temps running the car hard and never had a problem with cracking. As with anything no guarentees but it worked for me. Anthony '71 510 wagon---'91 Toyota Supra Turbo engine Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 28, 2002 Share Posted March 28, 2002 If it is just a crack, couldn't you try brazing it? Actually the guys before me sound much more knowledgable. But WTH, if the only alternative is to buy a new one it might be worth a try. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 29, 2002 Share Posted March 29, 2002 I welded up some water passages on a set of Cleveland heads to make a quasie-BOSS 302 head. John's info is pretty close. I did not preheat, but as expected I did have one tiny problem with the weld cracking until the heat finally "set" into the casting (so yes, preheating really is necessary). The higher the nickle content the better, but, also the more expensive the rods become. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted March 29, 2002 Share Posted March 29, 2002 FWIW - my welding instructor said he did a racer's head (1/4 miler) once that had cracked - right after he had speant megabucks on porting etc.... Some of the guys at the VoTech school - teachers AND students, knew exactly who he was talking about - the guy still brags to this day about our instructor saving his head. He pre-heated, brazed and cooled down VERRRRYYY slowly (had heated sand in over and buried the head in it! He seems to think that the slow cooling process after the weld is critical (aligning the crystalline structure). I've seen the artistry (and ease) that is this guy's trademark, and his commitment to nothing sloppy, so I pay attention when he drops any suggestions..... This was 4 years ago and the racer is still using those heads Quote Link to comment Share on other sites More sharing options...
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