1972 Chevrolet Corvette Scarlett Project Car - EFI Fuel System

In the Tank - Project Scarlett gets a new EFI fuel system

Jeremy D. Clough Jul 1, 2014 0 Comment(s)
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It takes three things to make an engine run: fuel, air, and spark. While we had previously upgraded the fuel system to handle the Zex nitrous oxide system on the original small block, it became clear that our 600-plus-horsepower 416 was going to be a lot thirstier. This meant we needed a comprehensive replacement of the entire fuel system to something more EFI, and horsepower, friendly. As with the rest of the work on Scarlett, “we” consists of Tray Walden, owner of Street Shop, Inc., who has graciously offered his shop and services for the project, and me.

We started by replacing the fuel tank with a stainless one from Rock Valley that we ordered through Street Shop. It came with an Aeromotive A1000 in-tank fuel pump already installed and was significantly larger than the factory tank. Unlike the factory tank, which feeds from the bottom and doomed to leak at some point, the Rock Valley tank inlet and outlet are located on the top of the tank, and the pickup is protected by a swirl-shaped shield to keep it covered with fuel even while cornering.

A perfect storm resulted from the large size of the factory filler and the slightly constricted access to it that resulted from using a Le Mans-style filler. The raised height of the larger tank made it virtually impossible to line the filler up with the opening in the decklid. We could line it all up, but once we start cranking on the straps, the tank would rotate out of place, trapping the fuel cap. Ultimately, Tray welded up a narrower filler neck from a '54 and bolted that into place. Once tightened up, it all lined up perfectly.

Since we're using a FAST XFI computer, that is capable of running the motor on gasoline, LP, compressed natural gas, and E85, we purchased the GM flex fuel sensor required to run the motor in flex mode. Although I'm not dying to run Scarlett on E85, since you never really know what's coming out of the fuel pump anymore, it seemed like cheap insurance.

With everything in place and tight, we hooked up the positive and ground wires to a battery charger and ran the pump, and used the Aeromotive regulator to crank the pressure up to 65 PSI. We then inspected the new system for leaks and tightened where needed. With that, our C3 was one step closer to hitting the road.

Original Fuel Tank 2/23

01. Here’s the original fuel tank along with the steel straps, rubber boot, and drain assembly that went around the stock filler neck. Our Rock Valley tank came with new straps that had to be cut to length and shaped. We also opted to replace the decaying rubber bits with new reproduction pieces.

Factory Tank Rock Valley Tank 3/23

02. You can see that the factory tank is bit different than the new, larger, Rock Valley tank. Made for a fuel-injection equipped car, the Rock Valley tank came with an Aeromotive A1000 in-tank fuel pump already installed, as well as a bung for a return line. While the rest of our fuel system was AN, the bung was 1⁄2-inch pipe thread, requiring an adaptor.

Stock Fuel Gauge Sending Unit 4/23

03. Since part of the Rock Valley tank’s greater size is in added depth, using a stock fuel gauge sending unit wasn’t possible since the gauge would read “empty,” long before the tank actually was. Instead, we had a custom sending unit made that was the correct length for the deeper tank. Unlike the factory float-and-arm arrangement, the sending unit has a captured float design.

90 Degree Hose Ends 5/23

04. Clearance, always a problem with a Vette, was one of our concerns with both the feed and the return lines. To make sure we had enough room between the fuel tank and the body, we used 90-degree hose ends and checked everything with a straightedge prior to assembly.

Cork Gasket 6/23

05. We used the original-style cork gasket for installing the fuel filler neck, and stainless screws. While we started with the fuel filler neck that came off the old tank, only blasted and painted, clearance issues ultimately caused us to replace it with one Tray welded up using a narrower ’54 Corvette filler neck.

Fuel Tank Assembled 7/23

06. Here’s the fuel tank assembled and ready to go in. We made life easier by attaching the lines to the pump before putting the tank in place. That meant we needed to figure out the lengths of two hoses before installation so that we could install the fittings on the other ends. We could have just installed the new ends with the hoses hanging under the car, but, as you’ll see, it’s much easier to install the AN fittings on a bench. We also got the wiring ready to go. The Aeromotive A1000 pump will easily feed our hungry LS engine.

Tank Straps 8/23

07. In addition to setting up the new straps to hold the tank into place, we used a different crossmember that would accommodate the added depth of the larger Rock Valley fuel tank.

Speed Flex Hose 9/23

08. Most of the fittings and the fuel hose itself were provided by Earl’s Performance Plumbing. We used the Speed- Flex hose, which is ethanol-compatible, and black Ano-Tuff fittings to make sure the system would work with whatever fuel we put it in. In the -8 size, the hose came in 33-foot lengths, and we wound up with about 4 feet left over. We wrapped the hose with tape and used a cutoff wheel to get the hose to the right length.

Brass Fitting 10/23

09. The tape was left on until the brass fitting was fully seated. Take care with the braided stainless wrap since it can really tear up your hands.

Push Lock Hoses 11/23

10. The AN-type vise blocks really made this job easier, as did coating the threads with lubricant. If you want to save some money, and some hassle, Earl’s offers a line of push-lock hoses and fittings that work well for fuel lines.

Aeromotive Fuel Filter 12/23

11. Once we routed the “out” fuel line, we fed it into an Aeromotive fuel filter that we mounted to the frame crossmember. The rubber wrapped filter clamps were also sourced from Aeromotive.

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