C10 Fuel Tank (1973-87)

No Limit Engineering

1973-87 C10 Fuel Tank & Rear Crossmember

One of the major bummers that can be found on a ’73-’87 GM truck body style is the “saddle” tanks that sit outside of the frame rails on both sides of the truck just behind the cab. This design has even proved deadly, as the tanks are only protected by the bedside sheet metal which has proven to not be enough protection to withstand a side impact crash.

More important to the truck enthusiast is the fact that if one would like to install a four link suspension to allow their truck to gain a horse-power advantage or an adjustable suspension stance, those god awful tanks are just in the way and need to be removed.

Besides, if you happen to own one of these trucks, or have had owned one in the past, you are very aware that having to stop filling one saddle tank up with fuel only to then have to get in your track and turn it around to fill the other side tank is just a big pain in the butt. To add another weakness to this dual tank design is the fuel tank selector switch also has proven it’s self unreliable when it reaches an older age, which in many cases, leaves you stranded with a full tank of fuel on the other side.

In the past, some manufactures have made replacement fuel tanks that are mounted to the rear of the axle. This design has been a by far better design not only due to the fact that the tanks are protected by a rear cross-member, but also the fact that both sides of the frame rails are clear to affix a mounting point for a bracket system that can be installed with a new suspension. Another advantage is the weight factor of moving the fuel tank behind the axle which will make the truck ride better and could even help with traction.

Now the down side of many of the manufactures design of these fuel tanks is that the stock cross-member remains in place which makes the tank size a bit on the small size. Besides, the factory cross-member isn’t really all that strong anyway and wouldn’t offer much protection, or weight load capabilities.

To fill the void left out by past designs, the staff at No Limit Engineering has improved on the designs from many manufactures of the past by updating their own design for the ’73-’87 replacement fuel tank. The tanks are hand built from aluminum for a long service life and feature a baffled design to prevent fuel from sloshing while driving. Every tank is “Tig” welded, and “pressure” tested to ensure a solid “leak-free” unit. The kit also includes two steel cross-members that replace the stock cross-member adding strength to the rear frame section and some additional protection to the fuel tank.

Available as either a carbureted version for the older vehicles, or as a fuel injected version, the design of this tank allows you to grow into an electric fuel pump if required without ordering a new tank. No Limit also offers a “drop in” style fuel pump that is rated high enough to run the majority of modern EFI systems.

Let’s take a look at how their made, and what is involved on installing one of these tanks.

C10 Fuel Tank
C10 Fuel Tank

All of No Limit’s fuel tanks are made out of aluminum, and our “Tig” welded by hand one at a time. This new model was deigned specific for the ’73-’87 GM truck family. It can also be used with most after market suspension systems such as our project C-10 that sports a Porter-Built rear step notch kit.

C10 Fuel Tank
C10 Fuel Tank

The kit comes complete with all the mounting hardware fuel fittings, and fuel filter, and two bolt in cross-members.

C10 Fuel Tank
C10 Fuel Tank

A major feature of No Limit’s design is the baffle system that is built inside of the tank to prevent fuel from sloshing during cornering or under acceleration. Referred to as “bulkheads” each one is slid into place and welded to the outer skin of the tank. This will also give the tank some strength, and prevent an explosion if the tank is crushed by force.

C10 Fuel Tank

Our application calls for a carbureted version, but if you plan to run an EFI system in your vehicle, No Limit offers a “drop in” style electric fuel pump capable of running most modern EFI system. If you also take a look at where the pump fits in relation to the bulkheads, they surround the pump which will direct fuel towards the pump providing a constant supply of fuel.

C10 Fuel Tank
C10 Fuel Tank

With the bulkheads set in place and the side walls tacked to the main skin, the lid is placed over the structure. Next the fun part of welding all the seams up begins which takes a skilled craftsman with years of seat time with the Tig torch to get a clean strong bead of material over the seams that won’t leak.

C10 Fuel Tank

The next items that need to be installed are the fuel filler neck, and fuel sending unit ring, and two “bungs” like we see here in this photo. There is a bung on the top, used as a vent, and a “feed” on the bottom to ensure that our mechanical fuel pump will maintain the supply needed for the engine to run on.

C10 Fuel Tank
C10 Fuel Tank

Before every tank leaves No Limit’s production facility, they have to pass a pressure test to ensure that the tank is leak free. An air valve is threaded into the vent bung while all the other openings are plugged so that the tank can be pressurized. Then some good old soap and water is sprayed over all the seams. If there’s a leak, the air will escape through the hole and cause it to bubble warning the weldor of a failure before the customer takes delivery.

C10 Fuel Tank

To install the tank you’ll need to remove the bed of the truck to access the factory cross-member. This cross-member is weak at best compared to the replacement ones provided in the kit from No Limit.

C10 Fuel Tank
C10 Fuel Tank

Held in place by a series of rivets, the removal process begins by using a grinding wheel to sand down the rivet heads until there flush with the frame. Then using a hammer and punch, knock the remaining part of the rivet through the frame.

C10 Fuel Tank

Once you knock out all the rivets, the cross-member will slide right out of the frame.

C10 Fuel Tank

A section of the rear portion of the frame flairs out right where the tank needs to sit. This will need to be trimmed to give you enough room on both side of the tank allowing for a better fit. Using a straight edge ruler we drew our mark and removed the extra material with sawzall.

C10 Fuel Tank

To match the rest of our powder-coated frame, our cross-members made a stop by Ludikrs Kustomz where they were sprayed to match the rest of the frame. Fitting the part in place proved to be a bit tough after the powder coating build up made things a bit tight. The cure was a few good smacks with a rubber mallet. At this point you’ll want to leave the hardware loose until the front cross-member and the tank are installed.

C10 Fuel Tank

The front cross-member gave us the same fight, but when it was over, the hardware fell right into place, and was easy to snug up.

C10 Fuel Tank

Now the tank is fitted from the bottom of the frame. The front mounting tab that is welded to the tank fits over the front cross-member giving it more stability than as if it was held onto from the under side. The rear however is held onto the rear cross-member from the bottom, making it easy to remove the tank without pulling the bed back off.

C10 Fuel Tank

After the tank is set in place to your liking, you’ll need to drill the mounting flange on the tank so that the mounting hardware fits though the frame. Once this step is finished, use the mounting hardware to hold the tank in place.

C10 Fuel Tank
C10 Fuel Tank

Repeat the same step that was used to mount the rear flange for the front flange. Be sure to tighten down all the hardware on both flanges keeping the tank in place.

C10 Fuel Tank

With all the tank hardware held in place be sure to go back and run the rear cross-member hardware in place. Remember that the top hole allow the bed bolts to run though the frame, so for now just install the bottom fasteners.

C10 Fuel Tank
C10 Fuel Tank

Be sure to use some Teflon tape to prevent leaks while plumbing our system. Once tight side over your fuel supply hose and vent hose and tighten down the clamps to keep them tight.

C10 Fuel Tank

Success! Now you can hold the same amount of fuel in one tank without the hassle of turning the truck around to fill the other tank. That in itself makes this a great upgrade. Hey but don’t forget that you now have room to change suspension, while providing some safety to your truck , plus look at now well the tank and No Limit’s “drop out” battery boxes fit on the frame!