Adding second fuel tank and efi fuel pumps

[silver97]

I have a 87 truck that has only the driver side tank. I would like to install a second tank on the passenger side. Ideas on the fuel filler? I was thinking i could just use a hole saw and put in a fuel filler from a mid 70's truck.
Also I plan on running EFI that uses 58 psi. I'll take some suggestions on fuel pumps, plumbing, and the fuel gauge. I though about plumbing both tanks to a single surge tank style fuel pump but the gas would have to be equal volume in both tanks all the time. I think there needs to be a crossover pipe and pull from one tank to the fuel rail.

 

[hoagster]

Go to tanks inc. and look at all their info. It will help you make an informed decision.

 

[Broken85]

Good luck on the fill spout, but these are the pumps you want to use and the pollack valve that you need. These pumps will work with existing tanks and don’t need return lines. I added my wiring diagram for this that I made when I turned my dual tank truck into a Sniper EFI to run the pumps with relays instead of direct power. Make sure you get a tank selector switch for an 87 as that is the full time switch compared to any other year that is just monetary.

I also threw in the wiring diagrams (I think) for 87 and pre-87. If you use my diagram, and run it like a pre 87 setup I think it is a lot more straightforward.

Good luck. Let us know if you need more help

Holley 12-308 1973-87 GM C/K... https://www.amazon.com/dp/B07QRYGMP7/

ACDelco U7000 Professional Fuel... https://www.amazon.com/dp/B0013FY5KW/

 

[TotalyHucked]

No way I'd cut the bedside. I plan to add a second tank to my truck as well and do a crossover pipe with a similar fill to one of these. There's a ton of different versions of this from different places.

Inside Box Panel Fuel Filler - 67-87 GMC Chevy Truck

Shop Inside Box Panel Fuel Filler - 67-87 GMC Chevy Truck from LS Fabrication. Precision-engineered, high-quality products built for durability, performance, and perfect fitment.

lsfab.com

The pass side tank would then just have a simple transfer pump installed with another hose to fill the driver's side tank. The driver's tank would be the one feeding the engine. These are some pics I've saved over the years to use as inspiration, can't recall who's truck this is

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[Grit dog]

Go to tanks inc. and look at all their info. It will help you make an informed decision.

Wow, they’re pretty proud of their squarebody tanks!

 

[Grit dog]

@silver97
Aesthetics may or may not play a role in your decision, but from a functional standpoint, I cannot think of a single reason you would not want to go with one of the 3 oe type configurations. (Single saddle, double saddle or rear blazer/burb tank)
You can do saddle tanks with a single high pressure exterior mount fuel pump no problem. Or you can get high pressure in-tank pumps for any of the oe style squarebody tanks as well.
This topic comes up once in a while and I’m always astounded at some of the backwoods “solutions” that are brought up. Especially anything involving manually transferring gas from one tank to another or creating a crossover for saddle tanks to act as one big tank.
There’s many ways to skin the cat and get a running truck out of the deal, including bungee cords and a plastic gas can…lol.
But imo there aren’t any advantages of any of these unconventional redneck engineered configurations that I can see. Only risks like putting holes and hoses in the bottom of tanks to create a potential 20 gallon leak or having a system that can overfill and spill if left unattended.
Just things to think about.
And if you do punch a hole in the bedside for a new saddle tank filler, at least please put the hole in the factory location so the next person doesn’t have to slice and dice their bed side to fix a hole in the wrong spot! (Like I’ll have to do with the 77 if I ever need to replace the aftermarket saddle tank or before painting it.)

 

[TotalyHucked]

Also, for fuel pumps, legit Walboro (there's lots of knockoffs unfortunately) or Aeromotive are my go-tos for pumps. Don't forget to factor in the GPH rating, not just the 58psi. I run a Walboro 255 in my truck with a 5.3 LS and the "Corvette" regulator/filter combo. The Aeromotive 340 pumps are right at the upper end of what a Corvette regulator can handle. Any more GPH and you'll need a good quality aftermarket, adjustable regulator.

 

[silver97]

I don't think the crossover is what I will do. I see potential filling and leaking issues. I'm not worried about cutting a hole for the fuel filler. My truck is no show queen. I'm going to use the drop in tank fuel assembles for a 1987 but with walbro 255 pumps., double fuel filters and lines that tee into a single. I saw a multi position switch that let's you select your pump and gauge sending unit

 

[CountKrunk]

No way I'd cut the bedside. I plan to add a second tank to my truck as well and do a crossover pipe with a similar fill to one of these. There's a ton of different versions of this from different places.

Inside Box Panel Fuel Filler - 67-87 GMC Chevy Truck

Shop Inside Box Panel Fuel Filler - 67-87 GMC Chevy Truck from LS Fabrication. Precision-engineered, high-quality products built for durability, performance, and perfect fitment.

lsfab.com

The pass side tank would then just have a simple transfer pump installed with another hose to fill the driver's side tank. The driver's tank would be the one feeding the engine. These are some pics I've saved over the years to use as inspiration, can't recall who's truck this is

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Thats a slick lsfab product that's for sure.

How would the crossover tank setup work? Two fuel gauges? A manually activated pump to pump tank a to tank b?

Mine has the fuel cap/tube that goes 6" then ends lol. Second tank was removed years ago it seems.

 

[TotalyHucked]

Yeah, single fuel gauge and a manually activated sump pump to fill the primary tank. When you pump the secondary into the primary, you just watch your gauge go up and turn it off when it gets near full. My buddy's '86 is this way and works great as long as he doesn't get distracted going down the road and overfills the primary tank lol. It's happened several times, he's covered the front of my truck in fuel several times But he only uses the secondary tank on long trips. Just fills it full, fills the primary tank and he can safely go 400mi.

 

[CalSgt]

I don't think the crossover is what I will do. I see potential filling and leaking issues. I'm not worried about cutting a hole for the fuel filler. My truck is no show queen. I'm going to use the drop in tank fuel assembles for a 1987 but with walbro 255 pumps., double fuel filters and lines that tee into a single. I saw a multi position switch that let's you select your pump and gauge sending unit

It’s your truck and your money but…

IMHO, Plunging a hole in the bedside with a filler tube poking out will look like a tweaker did it even if you try to make it look clean.

You may be able to find a patch panel with the fuel door attached and the filler tube support on eBay or a junk yard. Maybe AMD sells the panels new too. Wouldn’t be too much more work for a factory appearance.

You might also consider doing the EFI swap first and adding the second tank down the road to eliminate additional issues until you are certain the EFI works correctly

The factory 87 sending units can be modified to accommodate the EFI pumps, the fuel level sender will switch from side to side using the pollack valve mentioned above. You’ll can buy a ‘87 tank switch for in the cab or use a simple toggle, I think my valve came with a toggle but I used the factory switch.

The ‘87 sending units also have provisions for the fuel supply, return line and vapor line.

I replaced all (or most) of my fuel line and plumbed in a return using Earl’s Vapor Guard hose. Earl’s has any fitting you may need to adapt your EFI in.

You’ll need to plumb in a filter between the tank switching valve and the fuel rail.

 

[TotalyHucked]

^Agreed with @CalSgt, don't want it looking like a damned ole Ford lol. That's what they did for the forward tank on '73-79 trucks FROM THE FACTREE. Just cut a hole and sheetmetal screwed the neck to the bedside. Sticks way out and looks like

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[silver97]

Do the mid 70's trucks have a fuel filler door to access the gas cap ? Looking at the LMC catalog I thought it was just the cap outside of the bedside? I was going to use those parts.

 

[TotalyHucked]

The exposed round caps were '73-78. The square doors came out in mid-'78

 

[hoagster]

Wow, they’re pretty proud of their squarebody tanks!

Yes they are, but you can get them from Summit. I just used them for research!