I am working on this old fuel tank for a project and want to work out this large dent. It happens that the dent is in the area above the petcock, so I was able to access it thru the threaded hole with a small diameter (3/8) rod to work out some of the dent. I am at the point where I have worked a good bit out but have created a small high spot that really sticks up. Before I go any further I feel like I should address it. So I am thinking it needs shrinking. My thoughts are to heat it up with a small oxy/act torch and hammer it down. I am looking for some suggestions on how best to move forward with it before I screw it up.
Pic The area that is bare steel is the area that is raised. The area around it is still low, but not sure if I should continue pushing it out or address the high spot first.
Won’t hurt to try to tap the high down now. Maybe have an****istant hold the rod on one of the low spots as you do it.
I feel like it’s just going to push the area back down. There is not a good way to support the back area while tapping on the outside. That’s why I was kinda thinking that heating it may cause it to shrink without pushing the area around it back down.
It’s a pretty old tank that hasn’t had gas in it for a long time. Not to mention it’s sorta rusty inside. So I am planning on cleaning it out.
If the threaded petcock is below that area, could you build a rod/bolt that threads into the tank and hold the work area while you use a spoon around that high?
FWIW: I was on Project Transition in the machine shop at the Army Depot I was stationed at before I was discharged. As part of the initial safety training I was told about a local civilian who took a torch to a 55 gallon drum that hadn't had gas in it for years. It exploded and he was killed. Point was enclosed containers that once had gas even though they are now empty and had been for years can and will explode when heated with a flame. Your results may vary.
Yes, I would use a torch and tap it down. You cannot just tap the high spot down without the whole area being lowered. I would also fill the tank with water while taking the torch to it if I had any concerns about gas fumes.
Oh I definitely respect the chance it could explode and would clean it out prior to heating it up. In my younger years we routinely soldered small gas tanks that had leaks. We would wash the tank out with soap and water and then put the gas cap opening over the end of the muffler of a running lawn mower and wait till it got really hot and then soldered it. I guess the combination of cleaning it, heating it to evaporate everything and filling it with carbon monoxide made it safer. It was something my dad showed me when I was a kid.
Yup we did that same thing at the Ford dealership I worked in years ago. Do the same thing today and take another step by connecting Argon gas or Nitrogen into the tank so inside will not support an explosion displacing oxygen with the inert gas. Be safe!
Yep. The metal is stretched. Try heating small spots in a circle starting outside the dent and going round and round working your way towards the center. Each time you heat a spot it will expand and then shrink smaller when cools.
The petcock is off center from the dent and is not very big. I may be able to clamp the rod in a vice and set the tank on top but its tough to keep it in the same spot since the rod is so small.
Years ago I took an OT Austin Healey gas tank to the local 2 man radiator shop to have a leak repaired. They would hot tank the the gas tank and immediately make the repair as soon as it came out of the tank. But only one of the two would make the repair, the other had a tank flash on him and he no longer would work on them. Hopefully you'll be able to clean the tank sufficiently to remove any left over gas residue.
At the base of the bump. Watch your heat though. Look at the color. Medium red max. Any more and you might burn through. If you do you'll have to just cut it all out and make a patch panel. Some folks say to quench with water. It'll never be perfect again but with patience you might make it a lot better.
I see a smooth one for a 4.5” grinder available on Amazon. Any experience with that type? And would it help with the low area?
Dawn dish soap and hot water. Dry it out. You're now safe from fumes. Worried? Smell it. Yeah I said it, smell it. I welded a dozen gas sump pickups in bracket/street racer gas tanks. Drain, dry, soap n water, dry, done. Sometimes I'd soap n water twice if it still smelled too much (there's always a mild aroma). The dent, the lower areas will go back down with the highs if they're not addressed. Are you any good at pick n file work? Make a blunt pick out of ⅜ rod and tap up the lows. Afterward you can shrink with a disc (if you have one) or go to the torch method. What none of us can share either here or in person is how hard to hit it and indeed how to hit it. All I can share is don't grab the hammer up at the head. You'll just beat the steel with no moving force. Yeah,I see that a lot. Heat the high and go into a small circle, don't get it too red, coming back to the high. Tap it enough to get it to drop, a little at a time, reheating gently. What you're essentially doing is "crushing" the metal back to it's flat form. The heat around the high allows a place to go. This is all over simplified but that's the goal, push the high back in. At the end of it all you can try a heat quench process to get it closer but the stamping forces used to make that tank will work against you sometimes. Good luck, hope I helped move some thought cobwebs outta the way. Show us how you made out.
Shrinking disc is the safest way and you can control the shrink. When I was young and dumb I would throw a Match in the tank and turn my back to it in case it blow up, it amazes me I am still here.
A friend in SoCal had a friend in the desert out by 4-corners. He was a loner, but had some interesting cars. One in particular was a fiberglass copy of a Cisitalia sitting on an early Corvette chassis. Long story short, he torched the neck of a fuel tank which had been sitting in the desert for many years. I don't know who ended up with car......
When I was just a young pup starting out we had a welding shop 1 block from the shop. That welding shop did alot of fuel tankers back in the day. They'd contact Ralph, the welding shop owner, he'd tell them flush the tankers, clean them out and drop them off. Once they were there he'd let them set with all the top lids open for a couple days then climb on top of the tanker, stand between a couple of the lids, light his cigar and toss the lite match down into one of the holes. Most the time nothing would happen but every once in a while we'd hear a loud "WUFF!" sound and we'd know Ralph found one that wasn't cleaned out properly. That old man did it for years, died of a heart attack at a ripe old age at home. I'd never try or do it but back in the old days things were done alittle differently. ....
one more vote for shrinking disc. best thing about the shrinking disc is you can't make it worse even if you tried.
Finally getting a chance to get back to the tank. I made a tool that has a larger head on it and that I could bend to get it to line up with the dented area. It’s not directly above the petcock hole, more like a couple inches to the left. I made the tool to get a more precise hit. I also had a thought about using a powerful magnet I have to locate the head and hold it there as I hit it. Definitely seems to help. I have a question regarding heating the area to shrink it. Would a propane torch get it hot enough vs using the oxy/acy torch? I found small shrinking discs designed to go on a 4.5” grinder. Anybody have any experience using one of those? In the past I had only seen the bigger ones designed to be used on the larger 8”/9” grinders.
Never used the small one. I’m curious as well. Should work. Before I knew what a shrinking disc was, I turned grinding discs upside down to create heat. Did ok. The regular propane might fit it hot enough but will take longer. The small tip one or micro torch is used to repair hail and small dings.
The Jalopy Journal
