Cheap way to seal a gas tank?

we recently shortened our gas tank on our challenge car and are now looking for a cheap way to seal the tank. When we water tested it there were about 4-5 small leaks, which we rewelded. Unfortunately, they are still leaking and I'm under the assumption that we will have to add a sealer from the inside of the tank. I looked at the POR-15 kit, but it is too expensive to be used on our already budget tight car. Is there a cheaper way to do it?

Thanks for the help!

Welding/brazing should normally have done the job. Is a used tank from the junk yard an option?

Gas tank repair stuff. Clean the area really well (wire brush and brake cleaner or denatured alcohol) and apply the stuff to the outside.

I've sealed nearly pencil eraser sized holes with the stuff. You have to work quickly because when it sets, IT SETS. It's quite exothermic.

I've also heard of people using fiberglass resin, which sounds like basically the same thing.

epoxy fiberglass resin works well. pour into tank use as lil hardner as possible to still have it set up fully. seal tank. roll tank slowly in all directions will coat the entire inside. let set up and enjoy. have used it to coat rust on tanks that had it and were clogging fuel filters.

Eastwood sells this kit which works well. If everything's clean, just buy the white schmutz, not the $50 kit.

I suspect the Eastwood "white schmutz" is the same as Creem, available from your motorcycle dealer. The other two liquids are phosphoric acid (Metal Etch from Home Depot) and MEK.

However, that can get expensive for a full size tank (too much for Challenge pricing). I've been working on the fuel tank for the MG, and have found Permatex Liquid Metal Filler works well to seal small pinholes from the outside. I just lay down a bead over the weld and smooth it down with my finger. Cheap, too - under $4 at NAPA. The leak does need to be dry.

I've tried the two-part gas tank repair sealer putty, and I think it works better on big damage than on little welding pinholes. This stuff does have a shelf life, make sure you're using a fresh stick of it.

water weld?

That sure sounds like the standard gas tank repair putty.

You're almost there. Keep grinding and welding until the holes are sealed and the tank doesn't leak. Sounds like someone needs the practice.

Plain old JB weld work great, use the waterweld stuff for under the car and big holes reinforced with wire screen.

Kreem sealer SUCKS with the new gas they claim its been reformulated but still see loads of post on how bad it works. I used Caswells Dragon Blood kit on my Ducati earlyer this year and I'm imprested at how well it covered and how well it put up with vibs and heat so far.

Solder?

Probably goes without saying, but please be careful if your repair involves adding heat:

http://www.hotrodders.com/forum/welding-gas-tank-119062.html

I've been inside my MG tank three times in the last couple of months (getting tired of that...). Every time, I just filled it with water up to the brim and then cut it apart with a Sawzall. By the time that was done and I dumped it out again, there was no smell of gas at all inside and I was able to weld it back together after doing the work inside.

Thanks for all the advice guys! We ended up grinding and rewelding parts of the tank and it worked well. Turns out going to a higher heat setting worked better even though it was pretty thin gauge stuff.