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Building a 63-66 big car gas tank

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farna View Drop Down
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    Posted: Nov/26/2020 at 9:40am
I welded my own tank up for my 63 Classic wagon because I could find no suitable substitute. Pretty easy -- if you can bend metal and weld. I used 18 gauge steel, painted inside with a gas tank liner (Bill Hirsch).

 
Original tank next to fabbed unit. Note where the sending unit are. For simplicity I made the first 4-5" of the top angled so I could easily mount the sending unit so it wouldn't contact the floor of the trunk. Made for less bending and welding. I'm a KISS principle sort when it comes to engineering... (Keep It Simple, Stupid!)

 
Not quite finished. It was intended to be finished, with most of the top just bolted on. Even though I had a good 1/2" lip all around, I couldn't find a sealer that wouldn't wash out. I thought it too much for a gasket -- would have to be pieced, and may leak at joints, especially with age and gasket shrink. So I welded it and made a smaller access panel in the middle for the fuel pump and sending unit. The two tubes on the left are the fuel feed and return lines. The 1/2" curved tube on the right is a vent. Note that there is one on the original tank. The low filler pipe extends into the tank about 12" and is welded to the floor at the inner end for stability.

 
A universal sending unit is used. Ohm range needs to be 0-73 (empty to full). I used something like this:
Takes a bit of trial and error to get the float arm the right length and bent so that it reads decently. Mine will only read up to about 3/4 full when full, but when it's reading empty I have about 3-4 gallons left due to the slope of the bottom of the tank to the front and the rearward position of the float arm. I'm okay with it not reading all the way to full, it's slower going down at first if the tank is truly full. Having 3-4 gallons left at empty is an advantage too. I have a front to rear baffle, seen here and in the next fuel pump photo, but not side to side baffles. I should have put a small baffle near the end of the fuel filter sock and not made an angle cut at the lower front of the center brace/baffle. If I get to the empty mark and make a real hard left or right turn I can have a hesitation as the fuel pump sucks a slight amount of air. It's not much, only half a second or so, but it's enough to remind you that you'd better get gas soon!  Or just get more when close to empty, like a normal person does!!

 
Fuel pump is a standard 1989 Jeep Cherokee pump, held to baffle by u-bolts. No issues here! I'm running a 1988 Renix 4.0L, slightly hopped up.

After running it a few months and smelling gas fumes whenever I had much more than half a tank, I welded the top on and made an access panel. I used 1/8" thick bar stock to strengthen the perimeter of the hole. I also had to use bar stock around the panel itself, drilled through with the lower bars around hole edges (from underneath) tapped for screws. I ran it like this at first, and still had fumes even with a cork gasket! The 18 gauge just wasn't stiff enough to seal, but sandwiching between two pieces of 1/8" bar stock did the trick! So yeah, after taking the tank out twice after the original install I finally got it, and got good at removing the tank! Not shown is the 3/8" drain plug in the left front, just between front and filler tube. That came in handy!!

Edited by farna - Nov/26/2020 at 9:55am
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hogman Quote  Post ReplyReply Direct Link To This Post Posted: Nov/26/2020 at 12:23pm
IMHO, Looks Like a Fair Amount of Work, BUTT, It Looks GREAT Frank!!!!!!!    Thumbs Up  Thumbs Up  Well Done Sir..........





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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/26/2020 at 10:20pm
Nice tank!

1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T14
AMC pages: http://www.sr-ix.com/AMC/

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Post Options Post Options   Thanks (0) Thanks(0)   Quote troutwilly Quote  Post ReplyReply Direct Link To This Post Posted: Nov/26/2020 at 10:22pm
Frank, nice work.  I wish I could weld and fabricate like that.
If I could make one suggestion to anyone attempting this it would be to make the body of the new tank the same size (dimensions) of the original tank body, not out to the flange.  I notice you made yours as wide as the tank flange.  Reason I mention this is that I had a tank built for my AMX and the fabricator made it as wide as the flange (probably my choice).  This caused there to be very little space for the current exhaust pipes to pass along side the tank. So close that I will probably not be able to go any larger.  Not sure but I think I'm at 2-1/4" pipes now.  This may not be an issue on a Classic or single exhaust vehicles.
Bill O.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2020 at 6:07am
If I had run the exhaust out the back it may have been an issue, but I have a 2.25" single exhaust and turbo muffler installed as the original was. The 63-66 big cars with single exhaust (mine was originally a 195.6, now a 4.0L EFI) have the muffler mounted transverse right behind the axle -- between the axle and gas tank -- with the outlet right behind the rear tire (exhaust down driver's side, outlet on passenger side for sixes). I don't know how they ran dual exhaust on the 327s. I've seen it run with a 70s Camaro/Firebird two in/two out single muffler and exiting behind both rear wheels -- that's how I've always recommended it. It is a good idea to consider how the exhaust and everything else runs under the car when building a tank. It doesn't have to be the original dimensions (mine is also 1/2" deeper), just has to fit!   If you have 2.25" dual exhaust now there is really no need for anything larger, and I'd say that even if you had 2". Larger only helps at wide open throttle, so unless you race a lot larger can actually hurt cylinder scavenging at low speeds.

Any shop that makes duct work and most body shops can make on up for you if needed. There is probably a tank that can be easily modified, but it's hard to get actual dimensions on a tank and so many to choose from. The low front fill pipe makes it a bit hard -- tank has to be deep in front then taper down to the rear. If you don't mind a little body work inside the trunk a fill pipe can be run up and over to the original fill location, at least in anything but the wagon body. Can be done on the wagon, but harder since it would need a metal cover to prevent exposure to gas in a wreck. If concerned in another body it's easy to install a piece of sheet metal behind the rear seat. Even a piece of 1/4" plywood would make a good enough stop to prevent liquid gas from getting in the interior, and slow the spread of flames should it ignite (not likely, regardless of what the movies show!).


Edited by farna - Nov/27/2020 at 6:10am
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote First_Gear Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2020 at 4:10pm
Wow I feel your pain. That was allot of effort! I drove across the state to buy a gas tank off of a junk rambler when I found out mine was toast. I lucked out. The tank I bought was spotless inside when I inspected it. Best $50 I ever spent. I sometimes wonder what I can do to prevent rust build up with these modern fuels. Maybe add some marvel mystery oil to the gas, keep the tank full?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Dec/02/2020 at 7:04am
Get a tank liner like the Bill Hirsch stuff (https://www.hirschauto.com/Gas-Tank-Sealer-_-Repair/products/4/?gclid=Cj0KCQiAk53-BRD0ARIsAJuNhpty8dTubYEev3gFjqypJ70Z0W0J4UctvTqhZqQURaY2JyyaCahdfSoaAk_eEALw_wcB). It's not as good as the early 80s product they sold, but it's about the best available. I've used the POR-15 gas tank liner and it can work, but can also ruin a tank. You MUST get 100% coverage or fuel can get behind the lining, causing it to come loose. Then you have a big "balloon" in the tank that won't seal. Only way to get it out is to cut the tank open, then has to be welded back. Not pretty! I ruined a tank like that. The "20 gallon tank kit" wasn't quite enough to fully cover the 20 gallon Rambler tank. In all fairness, the 63 Classic tank might be 21-22 gallons though. But the results of a bad cleaning (I don't think that was my case, but could be...) or not full coverage is bad!! The Hirsch product goes on very thin and won't be an issue even if you don't do something right. Just make sure the inside of the tank is as clean as possible. The Hirsch product will seal over rust and scale, just has to be "clean" rust and scale! Using their cleaner is best, but any solvent type cleaner will work well.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Dec/02/2020 at 11:22pm
I used some other brand sealer, but the recommended tank size max sounded dubious, so I bought two kits, used both at once. Turned out to be only slightly too much as I recall, and do not regret it. AMC tanks especially old ones are very large, twice modern cars. One of those jobs you gotta do right, once!


1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T14
AMC pages: http://www.sr-ix.com/AMC/

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Post Options Post Options   Thanks (0) Thanks(0)   Quote al1630 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2020 at 11:19am
Wow, that looks really nice! I'll have to remember this thread if my tank ever goes bad. (Hopefully never)
The tank in my American was boiled out and I used the Bill Hirsch sealer, which seems to be working just fine, and I doubt I did the best job putting it on either.

Did AMC use such large tanks for marketing purposes such as good mileage + huge tank = long distance between stops?
Alex
1963 Rambler American 440H
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