Adding drain plug to gas tank

[MoPar~Man]

I'd like to add a drain plug to my gas tank. My plan would be to buy this:

It's brass. I would solder the flange to the bottom of the tank, then drill maybe a 1/4 inch hole in the center through the tank bottom, then use an appropriate rubber what-ever material, cut as a disk with the same diameter as the threaded flange and use it as a gasket seal, with the plug screwed in to force the gasket against the bottom of the tank. Using teflon tape on the threads of the plug for insurance.

Looking for a simple drain solution, easy to do, low risk of failure, minimal alteration of the tank, but still absolutely gas-tight.

The above item is generally known as a Garboard Transom Drain Plug (ie - for boats). It's about 2 inches in diameter, I imagine the plug is 3/4 inch. I would use a smaller version if I could find one.

The downside to this would be that prepping the tank and soldering it would disrupt / vaporize the galvanized surface and make it rust-prone.

Are there alternate solutions for this?

 

[GOLDMYN]

Be careful, even empty for years, the flumes inside can blow the tank sky high, don't ask my brother to weld it. LOL

 

[Justin Plant]

get some dry ice and shove it in the tank. that should force the fumes out. I Have Not done this myself. However, I've seen a good friend of mine weld a propane tank. He used this method. We all lived. : )

 

[MoPar~Man]

I have already electrolyzed my tank (using double-strength vinegar and hours of electrolysis) and have already soldered closed several holes, held a torch to the opening of the tank, I'm satisfied that the tank is quite inert. But nonetheless I have ordered a new tank from Van's - because it was recently mentioned here that it was on sale for $240 (USD) instead of the ridiculous $900 (CAD) that I'd be paying for a Spectra tank. But I digress. It would be the new tank that I'd put putting this drain plug on.

Aside from the drain plug, expect more questions in the future about coating / painting the tank (or not) before mounting it.

 

[commando1]

How many times in the car's lifetime under your ownership do you plan on draining the tank?

 

[livininharrow]

i have to agree with stan. why bother. i had a 55 desoto with a fuel tank factory plug in it. for shits and giggles i drained the tank and there was nothing other than fuel. 60 year old tank. not worth the effort in my opinion.

 

[mikedrini]

I'd like to add a drain plug to my gas tank. My plan would be to buy this:

View attachment 640504

It's brass. I would solder the flange to the bottom of the tank, then drill maybe a 1/4 inch hole in the center through the tank bottom, then use an appropriate rubber what-ever material, cut as a disk with the same diameter as the threaded flange and use it as a gasket seal, with the plug screwed in to force the gasket against the bottom of the tank. Using teflon tape on the threads of the plug for insurance.

Looking for a simple drain solution, easy to do, low risk of failure, minimal alteration of the tank, but still absolutely gas-tight.

The above item is generally known as a Garboard Transom Drain Plug (ie - for boats). It's about 2 inches in diameter, I imagine the plug is 3/4 inch. I would use a smaller version if I could find one.

The downside to this would be that prepping the tank and soldering it would disrupt / vaporize the galvanized surface and make it rust-prone.

Are there alternate solutions for this?

I bought a replacement tank for my 64 NY and it came with the drain plug already installed.

 

[MoPar~Man]

I don't know about which tanks come from which suppliers or retailers that come with a drain plug. Did you car's original tank come with a plug?

Funny how the LH 300M's (1999 - 2004) with plastic tanks, the '2000 M's came with plugs but not for the other years. It would be really cool if someone made repro 60's tanks in plastic.

I ordered a tank from Van's because of this sale. I didn't know there was an option other than Spectra. Neither one offers the tank for my car ('67 Monaco) with a plug. I ordered over the phone, talked to the sales guy for a bit, he said they have these tanks made for them in Taiwan. $240, plus $50 shipping to Michigan. I asked if they come with (or if they can come with) a plug, he said no.

 

[413]

Sorry don't want to sound mean but your plan to seal it is just nonsense. With nothing to hold that seal in place and pushing against flimsy sheet metal it won't seal very well or for long. And who is to say the plug will get tight at just the right time to put enough pressure on the rubber without pushing to hard and bending the unsupported sheet metal out of shape?

Now are those threads pipe threads? Then they will seal on their own. That plug you have looks like what is on the back of boats to drain the bilge.

1960-1962 Chrysler come from factory with a fuel tank drain plug. And the 1963-64 is a similar car and chassis so may just be the same tank.

 

[mikedrini]

I don't know about which tanks come from which suppliers or retailers that come with a drain plug. Did you car's original tank come with a plug?

Funny how the LH 300M's (1999 - 2004) with plastic tanks, the '2000 M's came with plugs but not for the other years. It would be really cool if someone made repro 60's tanks in plastic.

I ordered a tank from Van's because of this sale. I didn't know there was an option other than Spectra. Neither one offers the tank for my car ('67 Monaco) with a plug. I ordered over the phone, talked to the sales guy for a bit, he said they have these tanks made for them in Taiwan. $240, plus $50 shipping to Michigan. I asked if they come with (or if they can come with) a plug, he said no.

Yeah, got mine from Van's as well, Gas Tank -1964-1966 Imperial, 1963-1964 Chrysler, Dodge 880-Mod Tank

 

[MoPar~Man]

Sorry don't want to sound mean but your plan to seal it is just nonsense. With nothing to hold that seal in place and pushing against flimsy sheet metal it won't seal very well or for long. And who is to say the plug will get tight at just the right time to put enough pressure on the rubber without pushing to hard and bending the unsupported sheet metal out of shape?

Now are those threads pipe threads? Then they will seal on their own. That plug you have looks like what is on the back of boats to drain the bilge.

1960-1962 Chrysler come from factory with a fuel tank drain plug. And the 1963-64 is a similar car and chassis so may just be the same tank.

Perhaps a cut-away diagram will help:

The tank wall is shown in grey. The break between the grey sections is the hole through the tank wall. The plug flange is green. The yellow is the solder, bonding the flange to the bottom of the tank. The plug is red. The threads are exaggerated for clarity.

The small black piece above the red plug is the rubber sealing gasket. And as mentioned, the plug threads would be wrapped in teflon.

I probably won't use the boat drain plug, but instead this plumbing piece (known as a hex bushing):

 

[73Coupe]

I would put the flange on the inside with the bung facing out, then solder it.

Use hardware with pipe threads, no gasket necessary. 1/4 or 3/8" max. You don't want it to drain too fast.

 

[fury fan]

If you are wanting to drain a fuel tank on a recurring basis, why not just hook an electric pump onto the fuel pickup?
You won't get it completely empty that way, of course, but a little stale fuel at the end of the season will not matter when you fill up in spring.

That drain plug is a great way to get fuel splattered on you when you are taking it out, it'll be weeping and dripping at the last few threads of loosening.

 

[mopar preferred]

If you have to do this, you would be better off with an o ring seal under the plug head, rather than the rubber pressing against the thin sheet metal of the tank. It will deform and leak for sure, unless you have reinforcement inside the tank.
How are you going to control the gas coming out if you do drain it?
I would agree with @fury fan, use an electric pump first to get as much out as possible, then at least you won't create a flood of gas if you use the plug.

 

[Boydsdodge]

You could have a rad shop install a pet cock valve on a front corner of the tank so its not positioned lower than the tank bottom and susceptible to being hit, like how it is on a radiator. Now you can control the flow and not reinventing the wheel.

 

[3175375]

Likelihood of needing a drain is near zero. Spend your $ and time on other things.

 

[413]

Cars with fuel Nick filler behind licence plate. Park the car with rear wheels on 2x 8 blocks. 1 more on one side. Now you can insert a long piece of fuel line to the front of the tank on low side and use electric pump to empty the tank. Can get most out this way. Done it.

No drilling or welding.

 

[fury fan]

Or one of these would be a good idea, it's designed for this type of usage. (requires a female cap)
JIC is a good-sealing design, and easier to use than the NPTF. No tapered threads to wonder how much tighter you need to make it for it to stop weeping.
With JIC, when the tapered seats bottom out, just a hair more and it's done.

And, if you can get it into the top of the tank, you could remove the cap and put the electric pump suction hose right down thru it.
Although that risks sucking debris into your pump unless you add a filter.

Fuel Cell Bulkhead, -10AN Male, BLACK (FIT-483110): Bulkhead Fittings - Fuel Cell