intake mainfold repair

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hey guys, ive got an aluminum intake manifold that one of the cooling passages corroded so bad that a chunk broke off where it seals to one of the heads. as a LAST attempt to save this thing i am planning to try and build it up with some 4043 filler and my pt225. im planning to heat it up with my torch and keep it warm throughout the process. ive got an 1/8th red tungsten and plan to ball the end on the grinder. im guessing i pretty much need to run full open right? i havent attempted much alloy up to this point. so this will be a learning project. i plan to do my best to plane it true before install. if it works it works, if it doesnt ill head to the junkyard.\any pointers? im working on getting this thing as clean as possible and the final thing before welding im gonna clean the area with acetone.Millermatic 211weldpack 3200 squirtgunsquare wave 200victory journeyman kitHypertherm 30xptoo much other crap to listtinkerer extraordinaire
Reply:First grind out all the corrosion.   Yes you'll likely be running wide open.  Large piece of cast aluminum with a small machine isn't really what you want to be learning to tig aluminum on.  If you really want to save the manifold, you'll be better of to take it to a weld shop and have it done professionally.  Practice learning to weld aluminum on scrap before doing important projects.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:as a LAST attempt to save this thing i am planning to try and build it up with some 4043 filler and my pt225.
Reply:I believe member castweld would recommend preheating the entire manifold.  He typically preheats to 350F before welding and sticks it back in the "oven" when it cools to 290F.  When done, reheat to 350F for 30 minutes, turn the oven off and let cool slowly.  Machine as needed.He did a coolant passage weld repair on a head with it still on the engine but then he knows what he's doing too.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:It sounds like you've got a good basic plan, about cleaning it well, and being able to deal with distortion, which you'll probably get to some degree.  If you can restrain the work by bolting it flat during welding, that will help the bolted surface stay flat too.  But I realize this may not be practical.It will weld better initially (and distort less) if you pre-heat it.  You can just use a cheap propane-air torch if needbe to do this, it is remarkably effective.  You can also skip the pre-heat, it will just weld cold initially, (but will eventually get hot enough to melt and flow nice) and probably will distort more.If you pre-heat with a torch, I would focus the pre-heating on the area away from the weld area.  Think about if you welded without pre-heating it, what chunks of metal would remain cold, and would be sucking the heat away from your weld beads?  Those are the areas that you want to focus the pre-heat on.  So when your weld is cooling, that nearby metal won't pull the heat away from it as quickly.  A more gradual cooling of the entire piece will cause less distortion.I would dial in as much DCEN (penetration) as you can while still keeping it in AC mode, and hit it will full current.Access to a helium mix would be desirable - I've heard makes a smaller welder work like one much bigger, (the more helium the more heat, but may also result in harder arc starts) but you can probably get by on 100% argon.  I welded a pretty large (long runner ports) aluminum 4-cylinder intake manifold no sweat, either with or without pre-heat, with a 200 amp inverter welder (maxxed out at 80% DCEP) and 100% argon.  I do try and keep a sharp tungsten (with a flat ground on the tip), seems helpful if you need to focus the heat down deep into a crevice.  2% lanthanated seems to hold its point under heavy current the best.If you find an area when welding has dark black spots rise up to the surface from some contamination below, you will need to stop welding because those spots won't go away from heat, and scrape or physically remove them.  A carbide burr can work really well to dig out any pockets of nastiness encountered, but removes metal in the process.  (Luckily we have the means to just build it back up with filler though.)A utility knife is useful for scraping contamination off the surface.  Drill bits and also dental scalers/scrapers are great for scraping surfaces of the more difficult to reach areas, or reaching down into crevices or towards the bottoms of craters.  (things that a wire brush or burr can't reach...)Give it a shot.  I hear 4047 if you can get hold of some, has higher silicon content and flows better (and melts at a little lower temp) than 4043, and so may be more desirable for cast aluminum, although I've never tried it.  4043 worked fine for me.  Best of luck