Topic: to weld or solder/braze gas tank... that is the question

[timdhawk]

i need to fix/add material to my tank. I am cutting out the stock recessed tank cap and cover on a 78 SS tank. i will be "attaching" a new peice of steel in its place flush with a pop-up gas cap. i am sure that part will need to be welded but what about the new gas cap... should that be welded or should i braze/hard solder it the the new metal?

also i am thinking about cutting out a small portion of the bottom of the tank that has a series of pin-holes and replacing with new material as well rather than just relying on tank sealer.

same question... weld or braze/solder?

thanx

[PJ]

If the tank already has some pin holes this is just an indication as to the condition of the rest of the material, it is *very* thin in probably more than the one spot. I would start with a different tank.

You could soldier or braze the pieces into place but if you use either of these processes you have to keep the gaps of the two materials that you are joining to absolute minimum. Brazing can actually be almost as strong as an electric weld if it's done properly. Gaps in the material is a no-no! It is not a filler.

[troppo]

First of all make sure you purge the tank, they have a tendancy to blow up otherwise.......
I would TIG the new top in, better penetration with less spread of heat, you could easily braze the pinholes up, silver solder will work just as well, replacing the metal is best but not always do-able.
All depends on the skills you have or have at your disposal

[timdhawk]

the rest of the tank looks good... real nice and clean except for a small spot on a seam and a bend on the bottom. otherwise clean metal...

i can mig fairly well, but no tig!

[troppo]

Mig is fine, just that tig is better. With mig you get more distortion in thin sheet metal unless your very careful.
Where your damage is solder is probably better as theres less heat, therefore less distortion.
If your going to dothe filler yourself with a mig, make sure its a hot setting (quick deep penetration) and spot weld it.
I mean put spot welds at opposite sides of the weld, go back and forth as you weld to keep the heat distortion to a minimum.
You need to make sure your patch (or filler) panel fits closely with gaps no bigger than the wire you are using.
Make the patch, cut the hole for it in the tank (how you do it depends on the tools you have), tack it in place, tack the new filler neck in, slowly weld the patch panel in place (spots remember ) and then spot weld the filler neck in.
If your careful, prep well and take your time you should have a leak free patch with very little distortion (read little or no bog to make it look right)...
we love pics, remember that