Truck in question is a (mostly) 1951 f1. I’ve posted pictures before in other threads but can here as well if asked.

Okay so I don’t have the bed off my pickup yet so I’m not even entirely sure what’s under there. But I’ve been heavily discussing pros and cons to moving the stock gas tank with my father. I’ve seen threads where people discuss moving it under the bed, how that affects where the fill goes, having to remove a crossmember....etc.

But here’s my question if you got all new gas tank and gaskets and fillers...etc for the in cab tank location, wouldn’t my main issue be the sloshing sound? Because that’s my dad’s argument. He also says that from pictures he’s seen of the under bed mounted gas tank that it’s so close to the ground and would be more easily damaged in an accident at the rear of the truck.

Personally, I can see it both ways. The ease of keeping it stock, not having to move fuel lines, being able to use a stock sender for my stock gauges that I’m planning to use. I can also see how moving the tank could pose safety issues if rear ended at high speed. However I can also see an issue of being t-boned at high speed and the damage being to the cab at which it’s right behind me the driver. I’ve been in 3 accidents in my life. All at fault of other drivers. 2 times t-bone, and one time rear ended. The rear end was the least damaging but it was also in a slow speed construction zone. I do plan to drive this truck as often as possible. It’s not a show truck. I’ll paint it up and restore as much as I feel I want to do but it won’t be pristine.

I also have read where people will “box in” the cab gas tank. How feasible is this? Because I’m open to that and any other suggestions.

So, give me your opinions and thoughts. My father has driven vehicles with the tanks right behind the seats and said it never bothered him. I never have except for the few test drives in my own truck, and the smell is horrible. However I’m almost positive there’s a leak in the filler tube, if not elsewhere even.

Also, can anyone address my dads concern about the distance to the ground with the gas tank being moved to the rear. I’ve looked at buying one that’s made for a 51 f1 and a 70 mustang gas tank and seen all the measurements. But having that I don’t know the measurements yet of my truck I am slightly concerned about that as well if I’m being honest. I don’t plan on dropping my truck any lower than it is, but I do live and drive in an area with the most ridiculous gutters and dips in the road that you wouldn’t believe.

Thoughts? Questions? Concerns? Opinions? Let’s here em!

 

The stock cab location should not have any odor if the sender seals and filler hose is sound. The tank has baffles that minimize any sloshing. I've never noticed any sound.

In addition to affecting the exhaust routing, the under bed tank will also displace the spare tire carrier.

 

The exhaust was moved by the PO so that luckily wouldn’t be an issue. But you’re right about the spare tire. And I was thinking if there’s a smell that something isn’t sealed right. So thank you for your response!

 

As far as the rear mount tank..the 22 gal tank does not drop below the 3rd member or in my case the lower shock mounts (but I'm not running stock suspension, I removed the rear crossmember but it was replaced with a trailer hitch that bolted between the frame rails. It's made from 2x2x.25 square tubing that is much more substantial than the old crossmember. I fill through the bed floor. I'll link to the article to show you some pics and measurements. The loss of spare mount is a problem but mine will ride in the truck bed on a pad. And, you cal always opt for AAA. I'm trying to decide now on the width of the spare rim since I have 8" up front and 12" on back !!... There was a cost for the fuel sending measuring system... I used aftermarket gauges and had my Mustang sending unit calibrated to the Dolphin gauges and it's very accurate based on my experience. Hope this helps or at least gives you some info that you need.
joihn

https://jniolon.classicpickup.com/mu...ankarticle.htm

 

my tank is in the rear and protected by 1/8 to 1/4" in multi layers on all 4 sides i chose the rear because i am using fuel injection engine and wanted the fuel pump in the tank
besides copying dave was easy.
if i was mostly stock i would leave it in the cab save your time

 

Hi Marlyse,
Hmmm... Sounds like Dad has his mind made up but here are some thoughts.
1) Safety - If having a gas tank with 20 gallons of fuel next to you in the passenger compartment
is so safe why are there no modern cars or trucks with this set up? It has to make sense to put this as far
away from you as possible. The 22 gallon Mustang tank most folks use does not stick down below the frame.
Our's is protected by a metal frame on all sides. (The larger Bronco tanks do stick down pretty far).

2) Smell - A drop of fuel really stinks up a cab. We replaced the gaskets in the stock tank first etc. but it still smelled bad.

3) Sloshing Sound - It's unnerving to hear gas sloshing around next to you. It's noticeable.

4) More Room in the Cab - It gives you some space in the cab to carry a few things.

Challenges:
It makes running Dual exhaust out the back difficult.... not impossible but it certainly makes it harder.

It takes some work & money to get it done. $125 for a tank & another $75(?) for a sender & probably 2 weekends
of work to do it.

It can raise gauge to sender issues. You'll have to match the ohms from the sender to the gauge you want to use.
You'll also want to vent the tank to a charcoal canister to keep your truck smelling good.

Summary:
Patch up your existing stock tank & ride around with it for a bit & see if you like it. If you don't then
put one out back under the bed & forget about it. Personally it's one of the better modifications
we did to our truck.

Good luck over there.

Ben in Austin
1950 F1

 

I'm not advocating for or against moving the tank, it's a personal preference. There's a couple of things that bother me about most of the rear tank conversions.

First, and perhaps this is just me, as it seems lots of people do this without issue, but I have concerns with the structural integrity loss with moving/removing the rear crossmember as it relates to the boxing of the leaf spring hangers, and the rigidity and strength that modification changes. There's a reason the crossmembers and hangers were riveted together in the manner they were by structural engineers way smarter than most of us. No one seems to think about that when cutting them out to fit a gas tank in its place.

John's build is an exception, as he's not using leaf springs, but opted for forward linking control arms. There's no longer the suspension forces involved on the back of the frame as there was with leaf springs. That said, there are custom, aftermarket tank options that will install a rear mount tank without surgery, but they are more expensive.

Safety concerns from impact or collision damage is the other. Maybe this is a wash, either way. Studies found in cab tanks were most at risk with being an issue in side impacts where the truck was tipped over onto its side, allowing fuel to escape from the filler neck, running either outside or inside the cab. With the high center of gravity and narrow track width of our trucks, this was a real deal back then. Fumes in normal operation should be controllable with proper sealing. If you can smell gas inside the cab, you have a leak somewhere.

Rear mount tanks, and especially those with rear facing fillers suffer similar issues in rear end collisions. The farther back the tank is, the greater the risk. Tanks in modern cars and trucks are primarily found toward the center of the vehicle for safety. A lot of truck builders opt to delete the rear bumper and instead have a simple roll pan covering the tank. Even with a bumper, it's typically a small bar with simple bracketry that looks pretty. There's not a lot of protection back there from a modern F350 or giant Suburban front bumper.

These are just a couple things to think about. You can make your own decisions, but it does seem you've thought through a lot of them.

 

I remember when I was just getting into cars, a guy down the street had an old Chevy truck, tank in cab, towing a eautiful 55 Chevy. He got t boned at a blind intersection. His truck caught on fire, his race car, and him. He died. Dangerous ! You better believe it. Put that tank under the truck where it belongs. Chances of a rearend collision past making it past all that steel..... If you're really safety con cious , put in a Fuel Cell.

 

I got a ? For the more stock guys I used to be a slick guy (61-66 trucks)we always had a problem with our fuel tanks (in cab) they would over flow if full of fuel and parked in the sun or leaning over as parked on a side slopes do any of you 48-56 guys have this problem just wondering


is this a hijac

 

This truck was posted by a member on the HAMB a long time ago. He was in traffic on a SoCal freeway, got hit and it rolled a couple of times, went into the guardrail and got hit again by other cars. It didn't explode or catch fire. Look at the damage, the area around the tank (lower back of cab) is hardly touched. There is more steel reinforcement under and behind the tank than anywhere else in the cab. The tank sits on a major structural member. I have never heard sloshing, people who do need better exhaust (Smithy's). No gas smell. It's not a bad location IMO.

 

No sloshing sound , fumes or anything in either of the trucks . Each has the gas tank behind the seat .The tanks have 2 baffles in them . Make sure your connector hoses are good w/ tight clamps . IMHO the best place for the tank is where they are .

 

Many move the tank to gain leg room...seat can move farther back. If that is not an issue for your Dad, then leave the tank where it is.

 

Charlie,
Moving the tank from behind the seat, at least in a Bonusbuilt cab, will not provide more leg room with either an original seat or a replacement seat. The reason as the seat back will hit the back of the cab at the top before contacting the tank. If you installed an old true straight back chair in the cab it could provide more legroom, however that would not be a very comfortable ride! Car seats are always tilted back on both the lower seat surface and the back seat surface. In the pic below, the original tank is there and there is space between the seat back and the tank.

 

Thanks Bill, good to know. My experience is mainly with the F100 series.

 

I don't think you would gain any leg room in a 56 either, the seat back hits the back wall before it would contact the tank..it's just wherever you feel comfortable with where the tank is. What you gain is storage behind the seat if the tank is moved..