Jim Smart
October 11, 2016

When you consider the fuel mileage in miles per gallon of the average classic Mustang these cars were never much on range especially with carburetors, V-8 engines, and 3.25:1 gears. The most you could expect from a full 16-gallon tank was perhaps 250 miles or roughly four-hours between fill-ups. Long about 1970 Ford got smarter about Mustang fuel capacity and upped capacity to 22 gallons in light of thirsty big-block V-8s.

Through the years, enthusiasts have figured out the 22-gallon fuel tank was a drop-in replacement for that stingy 16-gallon wash tub. However, once enthusiasts have gotten the taller tank installed they’ve learned the fuel filler neck would not fit and had to be cut. Or, with help from a brute broom stick, they could bend the tank filler neck to fit the neck they had to cut.

California Mustang introduces a true bolt-in 22-gallon fuel tank swap for your 1965-68 Mustang where everything actually fits and without cutting or bending. A purpose-built fuel filler neck and tank that fit together perfectly and without modifications of any kind. All you have to provide are simple hand tools and a clean drain bucket for temporary fuel storage. We’re also going to show you a couple of additional options you can try in the interest of safety and security.

1. California Mustang’s galvanized, rust resistant 22-gallon fuel tank is specially designed to fit your 1965-68 Mustang. We look at this and think why didn’t something think of this before? It drops right in without modifications. It has a drain plug should you ever need to drain fuel. It is taller, which means your trunk mat or carpet may have to be altered or changed for proper fit.

2. Everything you need for this installation is included in the kit including sending unit/pick-up, hoses, filler neck, clamps, and all hardware.

3. This is the 1965-68 Mustang’s standard 16-gallon fuel tank with its flat-top construction. Problem here is fuel capacity. It won’t get you far.

4. Fuel is drained into a suitable receptacle and retained for reinstallation. Make sure you do this in a well ventilated area and keep all ignition sources away from the container and vehicle. Even a tiny static electricity spark will cause fire or explosion.

5. Fuel sending unit connector and hose are removed at this time. Be prepared for fuel drainage from the hose.

6. Fuel tank screws and bolts are removed at this time. Screws get a 3/8-inch socket. Two bolts at the rear along the tail panel get a ½-inch socket. The ½-inch bolts are a form of tank security. They also secure rear valance guards.

7. Pop-open fuel filler cap is removed next. Expect countersunk sheet metal screws and a stud/nut inside removed with a 3/8- or 7/16-inch socket. The inside nut is to prevent fuel cap theft.

8. Filler neck hose clamps have been removed inside, with the neck removed as shown through the tail panel.

9. Tank lifts out easily. It is suggested you wear heavy gloves for this step. Fuel tank edges are very sharp and can injure. Note this is an old 22-gallon tank conversion — a rusty tank that needs replacement.

10. New California Mustang fuel sending unit and pick-up are installed first. Use a light coat of wheel bearing grease on the O-ring seal to keep it secure and install the sender. Retaining ring is seated and driven clockwise until it stops.

11. California Mustang high-capacity 22-gallon fuel tank is installed as shown. All screw and bolt holes should line up making installation a snap. It is suggested you use 3M’s Strip Calk (also known as Dumb-Dumb in the industry) between the tank and body to isolate fuel slosh noise.

12. Tank hardware provided by California Mustang is installed next. Do not overtighten or you will strip out the screw holes.

13. Two bolts are installed along the tail panel primarily for valance guard security. They do provide some fuel tank security.

14. Fuel filler neck from California Mustang is a perfect fit. No cutting or bending required. It is suggested you locate clamp screws away from the trunk compartment where they cannot be disturbed or damage contents.

15. Fuel filler pop-open cap is reinstalled. Although the factory style pop-open spring is normally provided with these caps for originality it is suggested you use the separate filler cap instead for safety reasons. Always use a vented cap.

16. Our installed California Mustang 22-gallon tank looks sharp and is ready for clean fuel. It is always suggested you keep your tank full in the interest of corrosion prevention. Keep a bottle of Sta-Byl on hand to keep fuel fresh. Even in the wintertime during good weather, drive your Mustang to keep the fuel fresh.


Safety Options

There are two safety options we’ve seen practiced during fuel tank replacements through the years. One is the decision to bolt the fuel tank in using Grade 8 bolts, washers, and locknuts for the complete perimeter of the tank as added security should the unthinkable happen — a rear end collision.

California Mustang offers you the Rear Seat Metal Trunk Divider for 1965-70 Mustang, which replaces the fiberboard panel these cars were originally equipped with. The metal divider keeps trunk contents where they belong in a panic stop and isolates exhaust and road noise.

Another option for classic Mustang enthusiasts is Tank Armor, a protective steel fuel tank cap available from the fine folks at Tank Armor. You’ve seen Tank Armor in Mustang Monthly before. It offers perfect fit and an additional margin of protection keeping fuel where it belongs.

If you opt for a bolt-in fuel tank installation, which involves drilling mounting holes in the tank lip and trunk floor, go with 5/16-inch Grade 8 bolts, washers, and locknuts for your installation. Bolts, flat washers, and locknuts, which you can buy at any home improvement store, improve fuel tank security.
Tank Armor is a high quality, 11 gauge (1/8-inch thick) steel trunk floor cap designed to increase the strength of the trunk floor in classic Mustangs. It comes with all hardware and instructions needed for installation. Tank Armor puts a steel barrier over the gas tank creating a solid trunk floor, which effectively locates the fuel tank outside of the vehicle.
Rear Seat Metal Trunk Dividers are available from a variety of Mustang parts dealers including California Mustang. These steel barriers replace the original fiberboard barrier located behind the rear seat. Steel keeps trunk contents where they belong, also isolating road and exhaust noise in the process.