Under bed Fuel Tank

[Phipp]

Started building a new fuel tank38 gallon to fit between my frame rails under the centerline of the bed. Doing a 350 efi and turbo 400 swap in the very near future. I currently have a 16 gallon tank.Has anyone on here done this? Any Lessons learned advise would be greatly appreciated.thx Phipp

 

[PrairieDrifter]

Buy a suburban or blazer tank.

Unless you're really good at and like welding a lot.

 

[Phipp]

I have one it hangs down too low& won’t fit all the way back w/ my tow hitch.Guess I’ll be stacking dimes ringing in the new year

 

[Bennyt]

I have one it hangs down too low& won’t fit all the way back w/ my tow hitch.Guess I’ll be stacking dimes ringing in the new year

Great that you are able to design, build, pressure test, etc your own tank but if you want to save time there are several manufacturers that sell pre-made under bed tanks for these trucks: CPP, POL, Tanks Inc, Ricks, etc. On our '77 C10, I used a Boyd Welding tank as it was priced competively and did what I needed. While I did modify the hitch for other reasons, it didn't interfere with the tank. The main reason I wanted the hitch is extra tank protection.

 

[Grit dog]

Advice?
While I’m sure you’re talented and creative, you’re creating a solution to a problem that doesn’t exist. Or at least has a simpler solution.
Even with a short box you could use one of the 2 smaller Blazer/burb tanks with a trailer hitch (no spare) and add rear filler in the bed side.
Or add another 16gal on the other side and weld in a gas door or punch one out in the bed side.
Given the clearance limitations and exhaust routing challenges and fuel filler challenges, and access to the sender/pump/connections I’m surprised this seems like a good idea to you at all.

And like many I’d assume you’re “keeping this truck forever”…..until you aren’t. Then you have an unconventional fuel system that would be a deterrent to anyone knowledgeable who might buy it.

 

[Grit dog]

My 77 has an aftermarket saddle tank on one side. Likely because sourcing the parts especially brackets etc was either difficult, impossible or not financially feasible in the 70s when these trucks had only been out a few years.
It is solid and works but it is far inferior to a factory tank and hardware. Worst part is the sloppy hole in the bed isn’t in the same spot as OE so no chance of swapping in the future without cutting a big section out of the bed side and replacing.

 

[Phipp]

It's a lot of work for sure. As soon as it's done i'm swapping the 4.3 for a 1999 L-31 Vortec EFI 350 and turbo 400 both are built already. I don't expect to get more than 13 MPG 3.43 gears. The 38 gallon tank should give me about 450-525 miles to a tank. i will use the original fuel door since the trucks paint is only 2 years old so cutting thru the body to add another door isn't an option for me. I'm 61 years young 5'7" tall. A 4" lift on 33's is a bit high for my old bones. Deleting the origional tank will give me tons of room to install the electric fold out/down running boards. don't be hatin on the elderly I had an nice 87 GMC R1500 long bed 2wd w/ twin tanks, one of the many fuel lines ruptured and truck went up in flames, tried to save it, fought the fire got it out but not before it got up in the dash. that was a real heartbreaker. Theres only 1 Braided PTFE fuel line in this set up. Pics to follow. Happy New years all ! Phipp

 

[Phipp]

42”x25.25”x8.5” fuel tank in tank fuel pump Aces 340 LPH return less fuel system Aces EFI.

 

[boltbrain]

I got a tank off a Suburban and put it under the bed behind the cab. Didn’t need to weld anything. It has an oak flatbed so I cut out part of the bed and dropped it in. I did a lot of drilling underneath and made some special brackets. I put sticky rubber on the two sheet metal slings that hold it up similar to how it was in the suburban. It works fine. It was a lot of work though and the clearances aren’t much so I’ll need to check it every year. I think in retrospect I’d mount the spare on an overhead rack above the cab or maybe along one side of the bed jeep style, and put the 38 gallon tank in the rear between rails like was often done by GM without compromising safety, most say. I can send pics if you want.

 

[Phipp]

38 gal fuel tank installed. Today. Won’t finish the plumbing, wiring.& fulfill termination intill I do the L-31 EFI 350 & Turbo 400 swap.