Radiator repairers - solder?

For anyone that does radiator repairs... What is the prep and type of solder used? I had to fix one on my runnign stand and it's holding but I'm not sure if I "did it right". Any ideas?

Not expert, but I have used plumbers lead solder and a propane torch. If you have soldered copper plumbing pipes, it is very similar. Clean the copper/brass and use plenty of flux. I have also used a big electric soldering "wand". I have watched radiator shops do it in the old days and they had a wide propane flame they held the radiator tank over.

If yours is the early "round top" radiator, they are notorious for splitting the top seam, usually against the front support (how would I know?). I never had good luck sealing those, so would get a shop to "re-core" the whole radiator. You could also change to a later "square top" if correct doesn't matter.

Acid or Rosin core, I googled that once and have repaired a few using just a Bernz-a-matic torch.

For radiator assembly use 60-40 Acid Core. Get it as clean as you can then start cleaning it for real. Make sure you have an adequate heat source (a propane torch probably isn't enough). Then, when this seemingly simple task defeats you, find an old school radiator shop (a dying breed).

Fixing radiators is like fiberglass insulation and taping sheetrock. I can do it, but if there is any way I can afford to farm it out, I do.

Thanks guys. This was the 3 core deal have on my running stand and it was a couple tubes I broke plowing up to it. I used solid core tin & regular flux for sweating copper. I have a MAP gas torch and heat wasn't an issue, but it didn't flow well. Makes sense that acid core would be better. I normally fix anything I cam, but wouldn't think of retanking or recoring. We have a guy here who's good so he's doing my 65s V8 radiator for me.