Prepping an old gas tank for welding

TheBandit · #1 07-30-2010, 11:14 AM

In my engine swap research I've stumbled on this in-tank fuel pump setup from Tanks Inc (http://www.tanksinc.com/index.cfm/pa..._ID=6/art6.htm). I want to retrofit this or another in-tank pump to my original '70 Nova tank.

What needs to be done to safely cut, grind and weld on a factory steel tank? And what's the best way to clean it afterwards?

Defender Chassis · #2 07-30-2010, 11:58 AM

I have never modified a steel tank but I have repaired some aluminum cells. I remove all fuel and make sure inside is clean and dry. I then purge with some inert gas. Usually whatever is on the mig welder. I seal off all openings to make sure no air/oxygen can enter. Not sure this is the safest way but Im still here. I will be interested in seeing others responses.

Ever thought about buying a new tank to modify? Most can be had for underr $200. Cheaper than your top layer of skin or life. The stuff I fix is usually one-of that would take take substantially more to remake than to fix.

On another note, radiator shops will do repairs to tanks. Might be worth asking if they would prep iot for your welding. Not sure if its their cleaner or what that takes away the possibility for an explosion.

entropy · #3 07-30-2010, 12:17 PM

Remove every fitting.
Rinse several times with dawn & water.
Rinse once with muriatic acid and water solution. Cleans out everything.
Set it out in the sun for a day or two.
Rinse with water and cut and weld.

Admittedly I have cheated that a few times.

rbeckett · #4 07-30-2010, 03:39 PM

We always drain and wash with a dawn soap and water solution, then purge with the exhaust from a car and allow to set out for a day before refilling with exhaust and keeping exhaust filling the tank as we weld. Never had a problem, but I am sure there is a more correct way to do it. Never had a flash or pop when we did it, so I am sure we got all of the fumes out before we welded. Just an old country way that works for me.
Bob

Fab-Ex · #5 07-30-2010, 04:20 PM

I just left my tank out in the sun bone dry a while till the gas smell went away. When its 100 outside it doesn't take but a day or two.

flange · #6 07-31-2010, 12:09 PM

We used to get them steamed and then would exhaust gas purge during welding as mentioned before. Customers would sometimes complain about the time it took to do this. One of the old boys at the shop in response to this would tell them he would do it without prep as long as they would sit on it. Nobody ever took him up on the offer.

shaggy10000 · #7 07-31-2010, 06:11 PM

steam it. That's the most sensible solution for most. A hot pressure washer left in it for an hour will do the job. If you have one with a steam option that's even better.
I will admit in the past I've just stuck the garden hose in it and ran it for several hours, Dried it out with a heat gun and welded it. Not the best move but im still here.
Now i steam them and check them with an electronic sniffer designed for that.
I never purge them with anything. I think its a waste, unless you want to weld it without removing the fumes by other means.

Jpfab · #8 07-31-2010, 09:10 PM

I have a jug of emeilsefier (sp?) all you have to do is put a cup or so in a tank the size of a quad, about 5 cups for a nova tank, swish it around after caping all holes cover all the surfaces and dump it out. I always let it dry although it is not required. the only problem I have had doing it this way is the inside of some of the quad tanks I have fixed started to rust in a day or so.

It is good stuff my parts store guy gave me a gallon 5 or so years ago. Doing quad tanks I still have 1/4 of the jug left.

I typically put a match to it just prior to welding or brazing just cause I dont like supprises.

SomeGuyFromOlympia · #9 08-01-2010, 04:27 AM

I've always filled them with water....all of the way
If water is taking up all of the space, then there is no air, is there is no air, no fumes....right???

(Yes I still do the open flame in the hole just because we are all cringing when we weld on this stuff right)

I dump the tank, leave it in the sun, or throw a air line in there for a while to help it dry out

wyoming9 · #10 08-03-2010, 03:44 AM

If this tank was the factory one. being 30 years or so I would think about a new one for sure.

Unless the car was never driven

about the time you get it back in it will start leaking some where i won`t screw with out gas tanks and more .

TheBandit · #11 08-03-2010, 11:31 AM

Thanks all for the replies and suggestions. I may get a new tank as insurance, but I wanted to ask to get ideas on what's involved. I'm leaning toward draining and rinsing it out with some dish-type soap, then taking it to a radiator shop to get it cleaned up the rest of the way. wyoming makes an excellent point - this is a 40 year old tank and it may need to be replaced anyway. I wish I could find an inexpensive tank already setup for an in-tank pump, but all I can find are Rick's and Aeromotive's setups, which are $1k+ without a pump. I can do an Tanks Inc setup for a couple hundred and get a new tank for about $150.

JaysinSpaceman · #12 08-03-2010, 01:14 PM

You weld, build one. Tanks are not that hard to build. Just remember to pressure test and soap the welds to spot leaks before you fill it with fuel.

Jaysin

entropy · #13 08-03-2010, 01:27 PM

Quote:

Originally Posted by JaysinSpaceman

You weld, build one. Tanks are not that hard to build. Just remember to pressure test and soap the welds to spot leaks before you fill it with fuel.

Jaysin

Agreed!

TheBandit · #14 08-03-2010, 02:31 PM

Something like this?
http://www.streetrodderweb.com/tech/...ank/index.html

I will think about it!

wyoming9 · #15 08-03-2010, 04:26 PM

Is this a race car??? Fuel Cell??

have you put a fuel injected Big Block in the car???

is it still Carbed???

i had a 67 Chevlle LS6 that ran just fine with the stock fuel pump.

I would love to get back to the mechanical pumps.

i am curious why you want to do this ???

Will you be cutting an access hole in the trunk or under the back seat

TheBandit · #16 08-03-2010, 06:20 PM

I am doing an LY6 swap (gen IV truck 6.0) into my previously carbureted '70 Nova. I was using a mechanical fuel pump before. For the new engine I want an in-tank electric fuel pump because I don't like the noise from external pumps. The Tanks Inc setup is a relatively inexpensive way to get what I want and using my original gas tank would save me time and money that I could better put toward other things. Cutting an access hole in the trunk is fine since I can cover it with an access door and lay carpet over it.

This is a street car, not a race car. I intend to take it to cruise nights, make occasional road trips, and every once in a while go to the strip or take it autocrossing. I want to keep some amenities intact like a useable trunk and room under the hood for the original AC. I don't intend for this build to get too radical, but I look forward to putting a mild cam in it and playing around with VVT. I expect it to outperform my old smallblock by a longshot.