fuel capacity questions

[k7cdl]

wondering about some choices about adding fuel capacity. this might sound crazy but i really like my 454 for hauling stuff but this 20 gallon tank isn't cutting it. trying to come up with ideas for adding fuel capacity without taking up the pickup bed space.

[SkinnyG]

Add a second 20gal on the other side?

I added a second tank to my shortened-box '77.

[k7cdl]

thanks. i really enjoy this truck. it was top of the line back then. power windows, power locks,cruise control heck the factory a/c system still works

[Katrina/10]

If you add a 20 gal tank to the other side, you'll have more gas than a factory option dual tank. The ones I've seen came with two 17 gal. tanks.

Like the Wyoming brush guard.

[andrewmp6]

Yeah add the 2nd dual tank or maybe a rear blazer tank under the bed.

[k7cdl]

How hard would it setting up 3 tanks? Ya my truck doesn't need a deer guard being a 79 truck but still looks nice lol

[k7cdl]

Maybe I'm going to need to go ahead and think about bed tank. I was hoping for 100 gallons of as Wyoming towns are far apart for fuel

[67RS/SSx2]

My great uncle bought a 1984 Silverado C20 crew cab fully loaded new and I ended up with it. He bought it to tow a 33' fifth wheel and it did the job nicely.

He added a combo fuel tank/tool box across the front of the bed. It held 60 gallons. The truck also had the two stock side tanks so it could hold a total of about 100 gallons.

Even a fuel guzzler can go a long way on 100 gallons. Just hurts a bit when you have to fill up.

[hatzie]

Originally Posted by k7cdl

How hard would it setting up 3 tanks? Ya my truck doesn't need a deer guard being a 79 truck but still looks nice lol

In theory it shouldn't be too difficult. A little complex to visualize but here goes.

Two ACDelco 467513 Single Wire Fuel Tank Selector Valves and a pair of DPDT toggle switches.

Paired DPDT switch setup;
Both switches pole 1 used to select which valves are energized or at rest...

• Valve power is hooked from the fuse panel to switch 1 pole 1 common.
• Setting switch 1 to main will cut power to both valves regardless of switch 2 position.
• Setting switch 1 to AUX will provide power to the common lug of switch 2 pole 1. At this point switch 2 selects which AUX tank is used.
• When switch 2 is set to AUX 1 valve 1 will be energized.
• Flipping switch 2 to AUX 2 cuts power to valve 1 and energizes valve 2.

Switches 2nd poles automatically select which of the three senders feed the dash gauge.

• All three senders and the dash gauge signal feed will run to switches 1 & 2 on the 2nd poles.
• Dash gauge signal wire will be on switch 1 pole 2 common.
• Main tank sender will be attached to the switch 1 pole 2 terminal that conducts to common when switch is set to "Main".
• Switch 1 pole 2 terminal that conducts to common when switch is set to "AUX" will attach to switch 2 pole 2 common.
• AUX1 tank sender will be attached to the switch 2 pole 2 terminal that conducts to common when switch is set to "AUX 1".
• AUX2 tank sender will be attached to the switch 2 pole 2 terminal that conducts to common when switch is set to "AUX 2".

Plumbing
Valve 1 just as a dual tank system...

• Hoses from Main sender will run to rest position hose barbs.
• Hoses from Aux 1 will run to energized hose barbs.

Valve 2 will be downstream from valve 1.

• Output hoses from valve 1 are now input to valve 2 rest position hose barbs.
• Energized hose barbs will be attached to tank 3 "Aux 2".
• Output hoses of valve 2 will go to the engine compartment.

The K5 Blazer tank is max 31 gallons and the CK saddles are 20 ea. All three would be 71 gallon capacity.

Visualization of switch pair...

[k7cdl]

Oh my. Talk about great information. You have took a lot of time thinking of that

[hatzie]

Originally Posted by k7cdl

Oh my. Talk about great information. You have took a lot of time thinking of that

That one is easy. The motorized 81-91 valves give me a headache trying to visualize. They don't have a "rest position" and the gauge switching is inside the valve body.

[k7cdl]

thank you again very much for the great information. one last question where would be the best place for the 3rd tank, where the spare tire is?

[hatzie]

Originally Posted by k7cdl

thank you again very much for the great information. one last question where would be the best place for the 3rd tank, where the spare tire is?

Seems to be where everyone puts em. They'll fit there nicely. If I were doing it I'd make a cutout in the bumper behind the license plate and put a '70s flip down plate holder to cover the filler.

Other than towing I probably wouldn't keep much fuel behind the rear axle. It may have a tendency to make it waddle.

This is a BIG project. Not for the faint hearted. The wiring alone would take me around 7-9 hours and this is a fairly simple wiring job. 1 power wire to the fuse panel on a circuit that's energized in Start and Run. Six wires exit the cab. 2 valve energizers. 3 senders to the tanks. 1 fuel gauge wire to the main bulkhead plug. Ground straps at each tank.
Some Fab work at the rear for the tank hangers and filler neck.
Fuel feed and return line including new, modifications, and outright replacements.