How to Repair a Cast Iron Carburetor with Silver Solder

70 How to Repair a Cast Iron Carburetor with SSF-6 Silver Solder and an Oxyacetylene Torch

Customer Testimonial:

Dear Mike;

I just wanted to tell you about a repair that I made that I probably never would have even attempted without your SSF-6 Silver Solder. I have attached some before and after photos.

My customer sent me a cast iron body carburetor to repair that had a piece broken out of the casting at the threaded hole where the inlet fitting screws into. It was a 1/8 NPT fitting, and someone had just tightened it too much and broke the casting. The broken piece was long gone. Someone had previously tried fixing it with epoxy, but it had ultimately failed.

When I first saw it, I wasn’t even sure it was possible to repair without the broken piece, being such a small casting.  I was afraid the heat from brazing or welding would warp the part, then I remembered I had some SSF-6 Silver Solder leftover from a manifold repair that I had done earlier in the year.  I  figured I had nothing to lose.

I cleaned and prepped the casting, cut the threads off at 3/8 by 2 1/2 inch hex bolt and then threaded the shank with a 1/8 NPT die. I coated the threads of the bolt with graphite to keep the silver solder from sticking to it.   Then screwed the bolt into what was left of the hole until it was fully engaged into the threads.

I clamped the casting into a large vise to act as a heat sink, and using a #3 torch tip, built up the area with the SSF-6. After cooling for about 2 minutes, I carefully unscrewed the bolt. It had left almost a perfect set of threads in the SSF-6.

After it was completely cooled, I bead blasted the casting and ran a 1/8 inch NPT tap through the threads just to clean them up.  I assembled the carburetor and leak tested it and there were absolutely no leaks.  My customer is very happy, since neither the casting nor the complete carburetor are available any longer.  My only other alternative would have been to search for a used carburetor replacement.

Thank you very much from both me and my customer for a great product


Doug Long


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