Classic Performance Products 378 E Orangethorpe Ave., Placentia CA 92870

Classic Performance Products

Tri-Five Chevy High Capacity Fuel Tank

By Steven Rupp
Here's the scenario: You've been wrenching on your '57 all winter long with the goal to long-haul the Hot Rod Power Tour. The A/C is charged, cup holders have been installed, and your rims are wrapped in fresh rubber. Your only concern is that the 572 big-block under the hood gets 15 mpg on the highway. This means you'll have to stop for gas every 240 miles, and you just know that fill-up time will happen when it's least convenient. You've thought about dropping a bigger tank, but you don't want to cut up your trunk floor, lose your spare tire or have some gigantic tank hanging down under your ride. The guys over at Classic Performance Products considered that exact scenario and started working on a way to drop a much bigger fuel tank into a Tri-Five Chevy. What they came. up with is a 25-gallon stainless tank to replace the 16-gallon factory unit. It looks better, and more important, it installs without having to violate the factory sheetmetal of your classic Chevy. For the guy knocking down 15 mpg, it will up his range from 240 to 375 miles. And that adds a lot of flexibility to your cruising plans.

Here's the original fuel tank as seen from under the car. In addition to being unattractive, it doesn't utilize the space efficiently.

After we disconnected the fuel hoses and mounting straps, the old 16 gallon tank is removed. However, we left the spare tire well in place. The goal is to increase tile size of the tank without cutting up the car.

Once all of the original fuel tank mounting hardware is removed, we put the new 25-gallon tank up in the chassis for a quick test fit. This tank is fully baffled, made from 1/8-inch thick aluminum and mounts on beefy 3/16-inch flanges. All of the CPP tanks are pressure tested before being shipped.

The new sending unit after it has been set up for this tank, pictured with a new sending unit as it comes out of the box.

Here you can see the sending unit mounted in the tank. This billet flange is already tapped for both of the popular sending unit bolt patterns. There are several sending units available to work with the OE and aftermarket fuel gauges.

First we mount the new crossmember under the car.

The cross member is a two-piece telescoping design that hangs off
of the top of the frame rails. It is assembled finger tight until it can be set into its final location.

A measurement is taken from the rear of the tank mount to the front of the tank mount.

Using the measurement taken from the tank, the new mounting crossmember is located the same distance from the rear-frame crossmember.

We do the final prep work before putting the new tank into the car. Here the vent fitting roll over valve is being installed. If any fuel stal1s to flow through this valve, it will automatically close, keeping the gas where it belongs in the tank.

Using the new crossmember as a template several 5/16-inch
holes are drilled into the frame. Then 3/8-inch self-taping bolts are installed to hold the crossmember against the frame rails.

After the crossmember is bolted tight to the frame, the two bolts that control the telescoping action are tightened. This design allows for variances in the distance between the frame rails.

With the crossmember in place and the vent hose attached, the new tank is raised into position under the '57.

Using the tank as a template, 3/8-inch holes are drilled into the rear crossmember.

The tank is then bolted to the rear crossmember using these trick little nut plates that were included in the CPP kit.

Since this car has the original carburetor and fuel pump, one of the 3/8-inch fittings is plugged and the fuel line is connected to the other. If we add fuel injection later we can simply remove the plug and connect a fuel-return line.

A reducer is used to connect the new 1.5-inch kinkproof fuel-filler hose to the original fuel filler in the rear fender. The hose is routed through the original guide, then between the frame rail and trunk floor before it reaches the connection on the side of the fuel tank.

These two pictures show how the new 25-gallon tank fits between the rails next to the spare tire well and the Flowmaster exhaust system. The spare tire well, rear bumper, and rear fenders are all lower than the tank, so the tank can not be seen once the car is back on the ground. Even if your Tri-Five only knocks down 10 mpg, this tank will give you an extra 90 miles before having to pull over. Imagine the range if you have a fuel-sipping LS engine and a deep overdrive.