Which is the correct fuel tank ?

[Copakekid]

I have to change the fuel tank on the passenger side of my 84 C1500 long bed. I measured the old tank and it was a 20 gallon tank and I got a tank from LMC Trucks. I never measured the drivers side tank because no problems with it.

After the instillation problems with the tank, I started looking at the drivers side tank and it measures as a 16 gallon.

The truck has the RPO code NL2 for auxiliary fuel tank.

I know somewhere along the line somebody has been into the passengers side because the tubes on the sending unit had NAPA fuel hose on it.

How do I find out what the correct size auxiliary tank should be ? I'm going on the Hot Rod Power Tour in June and would definitely like to have 2 tanks.

 

[AuroraGirl]

I have to change the fuel tank on the passenger side of my 84 C1500 long bed. I measured the old tank and it was a 20 gallon tank and I got a tank from LMC Trucks. I never measured the drivers side tank because no problems with it.

After the instillation problems with the tank, I started looking at the drivers side tank and it measures as a 16 gallon.

The truck has the RPO code NL2 for auxiliary fuel tank.

I know somewhere along the line somebody has been into the passengers side because the tubes on the sending unit had NAPA fuel hose on it.

How do I find out what the correct size auxiliary tank should be ? I'm going on the Hot Rod Power Tour in June and would definitely like to have 2 tanks.

short bed trucks would get a 16 gallon but that means someone put a short bed tank on yoru truck at some point.
If you have long bed, your truck takes 20 gallon tanks. Get the right year and make sure your filler nexk and all that is right too

 

[Copakekid]

That's what I thought, but in looking up the tank in the LMC catalog it has a note that some Longbeds had a 16 gallon tank as standard, but it doesn't say what year.

I was totally confused after reading that.

I looked on RockAuto and they list a 16 gallon tank but it doesn't specify long or short bed.

With the great quality of aftermarket parts, the new tank mount doesn't line up with the hole in the frame to tighten the strap.

My day sucked.

 

[legopnuematic]

As far as I know, no 73-80 long beds used 16 gallon tanks, I do know that that began in the 80's, I am not sure however what determined if a long bed would get a 16 or 20 gallon tank.

The frame should have the holes for both tank sizes, the tanks all use the same position for the strap on the front (towards the cab), and the second brackets position is determined by tank size (If I'm not mistaken). On a long bed with 16 gallon tank they use a steel extension for the filler neck/vent, the neck should be able to be used for a larger tank with the correct molded rubber hoses.

Here's a still from a Watch Wes Work video of a 16 gallon tank in a long bed and the steel pipe extensions.

Also to note 73-80 the main tank was the passenger side, and from 81+ the main tank was the drivers side (not that it really matters in this case)

You must be registered for see images attach

 

[HotWheelsBurban]

Best of my recollection, our '78 GMC longbed had two 20s, and our '81 GMC longbed had two 16s. During the workday we'd just run it on one tank, but on road trips (or when gas was scarce) we'd use both. One of my jobs was to gas them up, and I'd have to climb in the bed and pull the hose and nozzle across; I was flexible enough then to be able to put the nozzle into the filler neck from the bed.

 

[Copakekid]

Thank you everybody for the quick replies.

With the 20 gallon tank in it doesn't have much clearance between the tank flange and the rear spring hanger.

I'll take a look and see what the fill pipe set up looks like on the 16 gallon tank. The fill hoses on the 20 that was in it does look like a hodge podge of hose.

 

[AuroraGirl]

Thank you everybody for the quick replies.

With the 20 gallon tank in it doesn't have much clearance between the tank flange and the rear spring hanger.

I'll take a look and see what the fill pipe set up looks like on the 16 gallon tank. The fill hoses on the 20 that was in it does look like a hodge podge of hose.

what length springs do you have? is your truck using gmt 400 springs? is your truck a lengthened short bed truck?

 

[chevytech87]

My 87 had two 16 gallon tanks, I swapped them out with 2 20 gallon tanks. Ordered the correct filler pipes and such from LMC after trying to re-use the old ones. Highly recommended, hodgepodge would be a nice way to describe my “custom” filler hoses before I got the correct ones!

 

[Copakekid]

I spoke to a friend who is retired and was a long time mechanic at a now closed GMC Dealer.

To the best of his recolection, it would be one 16 and the auxiliary would be a 20.

The truck is original and isn't a lengthened short bed. Everything spring wise looks to be in the original location, as there is no evidence of cutting or re welding.

I'm not sure what you mean by 400 springs. I have been out of the GM truck game since I got rid of my 85 step side 4x4 in the 90's. I had a 76 GMC 3/4 ton 4x4 in the early 80's that I kick myself every day for getting rid of.

I took another look at the 20 gallon tank I took out and it looks like it might be a factory tank.

I'm going to go with my friends advice and just put the 20 in. He worked on enough trucks over the years.

Thank you everyone that replied for your help.

 

[85K304SPD]

I have an '84 GMC K20 long bed that has a big tank on the drivers side and a short tank on the passenger side. Both appear to be factory.

 

[SquareRoot]

what length springs do you have? is your truck using gmt 400 springs? is your truck a lengthened short bed truck?

I'm guessing the odds of either of those at about 1 in 3 quintrillion.

 

[AuroraGirl]

I'm guessing the odds of either of those at about 1 in 3 quintrillion.

Im just saying that if he has a long bed truck there shouldnt be a leaf spring in the way lol

 

[1lejohn]

My 85 K-10 long bed has a 20 gal on the driver's side and a smaller tank on the pass. side. I'm thinking it is a 16 Gal.

 

[AuroraGirl]

Someone probably replaced the driver side (main tank)since it came with the 16, they upgraded

 

[SirRobyn0]

short bed trucks would get a 16 gallon but that means someone put a short bed tank on yoru truck at some point.
If you have long bed, your truck takes 20 gallon tanks. Get the right year and make sure your filler nexk and all that is right too

IIRC The options were:

1 single 20
1 single 20 - 1 single 16
2 - 20's

My Dad had one such truck a 78' K20 with one 20 on the left and one 16 on the right. With that said I would install 20's on a long bed regardless of what came with it for the extra 4 gallons.