Aluminum brazing, soldering with Oxy-Acet

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Hi all,I decided to join your forum since the folks on the go-kart site that I frequent don’t have a great deal of welding knowledge. I want to expand my abilities with aluminum but I’’m limited to Oxy-Acet and an old Lincoln Cracker Box. I have two projects that I’m currently working on; porting heads and making intake manifolds. The heads require that I build up port wall thicknesses so that I don’t grind through when reshaping them and the manifolds require a brazing or soldering rod that has good capillary action and can flow between two flat mated surfaces. Here’s the post I put up on “Bob’s 4 cycle” Originally Posted by killforfoodWhat’s you-alls preferred methods for welding, brazing or soldering aluminum heads and manifolds?I’ve been playing with a zinc rod similar to what Charles uses (Alumite) to fill in combustion chambers but I’m not real thrilled with its characteristics. You have to heat the parent metal to just beyond the rods melting point (730degrees) and the rod is melted by rubbing it on the hot metal. It acts like solder except it has high surface tension and zero capillary action. That’s a good thing when you’re bridging gaps and plugging holes but sucks when you’re trying to penetrate a tight fitting joint of a manifold.http://www.weldcotemetals.com/dataFi...echAlumite.pdfhttp://www.kappalloy.com/alumite2.htmThere are three places I want to build up on heads. Two of the locations are outside of the intake port roof to prevent grind through. Also in the bowl roof area on the intake and exhaust.I assume I’ll need to remove the guide before welding the bowl and refit it later.I would like to build up the short side radius by welding or brazing but that area looks to be to difficult to get at.So any suggestion for welding or brazing these areas would be appreciated. I bought some flux cored aluminum brazing rod that looks like it will work good for building up heads but again it doesn’t want to flow into tight cracks. They recommend a minimum 1/16”-1/8” gap for good penetration.http://www.harrisproductsgroup.com/c...lloys.asp?id=2I also bought some Al-Braze Flux to play with. We’ll see if it makes things flow?http://www.harrisproductsgroup.com/c...les/fluxes.asp My main limitation is that I don’t own a tig or mig welder and I’m limited to a propane torch or Oxy-Acet torches.So anybody have a suggestion for a fluxed rod with good capillary action that will join manifold parts together? Joel
Reply:Flux cored products dont work well usually for lap areas due to not getting the flux where it needs to be, when it needs to be there. Using a seperate flux like Allstate 31 applied to the cleaned surfaces before assembly and brazing would be a good bet. Brazing alloy 4047 being the filler choice. Ford uses the material in production brazing of some of their cast intake parts. For the chambers I would actually weld the material in, using 4043 filler and Allstate 35 flux. Preheating the casting to about 450 F makes life easier. Avoid the zinc based flea-market rods.....Other sources of these materials in small quantity is www.tinmantech.com. They sell a product made by Brazing Technologies that they call aero-solder, and it might also work well on your intakes. Bobs is not the place to ask welding questions -Aaron
Reply:Thanks for the tips Makoman. I'll try both of those rods on some scrap and see if i can get the hang of it.Yah, I’m not real thrilled with the flea-market rod. I carefully tinned both sides of my joints and then melted them together.You can see in this photo that there was no fusion whatsoever. It’s like the two tinned sides quickly oxidized and refused to fuse with each other. The zinc filler rod was pushed out of the joint when pushed together and after grinding away the excess; you can see the joint is open and easily snapped apart. It makes me wonder if after tinning both sides I should have used some kind of flux before joining the pieces. What size Oxy-Acet tip should I try for welding? I’m thinking the smallest possible that will still melt a good puddle. I’m just concerned that I’ll melt my heads before I get the hang of it.The wife is gone all weekend. Can I use her oven for pre-heating?
Reply:Yeah a flux "may" have helped, but you really dont want the fatigue properties of a zinc alloy in that location. As for welding tips, actually go big. Bigger tips, welding hotter and faster will give you a smaller weld area. Its all in practice and heat control. What torch are you using?
Reply:I’ve got an old 315C torch with 00, 1, 3, 5 tips and a rosebud.Yah, we run the heck out of these motors. I sure wouldn't want my carb flying off on the middle of a race.
Reply:its like putting a stop leak in your radiatorof your truck or car it may work for a time(ive never seen it work) but sooner orlater your going to have to fix it the wright way
Reply:Ed, Not really sure what you are referring to, please clarify. As for the torch, yeah thats a bit of a monster but you can make do with it. I would use either the 1 or 2 tip for the head welding , and the 1 for brazing the manifolds. Its going to take a bit of learning and practice. I would go to www.tinmantech.com and pick up a booklet called aluminum weldng. Gives a bunch of good guidelines and procedures.