12. From the fuel filter we ran the line along the framerails, over the transmission crossmember, and to the front of the car. We ran the feed line on the passenger side and the return on the driver side, and mounted both, using clamps to attach the hose firmly to the frame. Keeping the hose ends wrapped in tape is a good way to keep them from getting scuffed, as they’re going to have to go through some pretty tight places.
13. Once we got the feed to the front of the car, we split it with a “y” fitting so we could run a separate feed to each of the two fuel rails, eliminating the crossover. As with the frame, we used clamps to keep the fuel line in place. To keep the two lines separate, we used a pair of clamps mounted on one of the screws that passes through the Vintage Air firewall plate.
14. When the motor was originally built, we used a crossover at the front of the motor to connect the fuel rails. While there’s nothing wrong with this arrangement, we decided to run a separate feed to each of the two rails. Once we had determined where the “y” was going to sit on the firewall, we built the feed lines that would run to the rear of the fuel rails. We used 90-degree hose ends on the fuel rail side of both lines, and a 45-degree for the one mounted to the bottom of the “y” to keep the two fuel lines loosely parallel.
15. The rear feed into the fuel lines was easy compared to the front, where we had to route two return lines into the regulator, and mount the regulator somewhere that the bottom-exit return line could go to the flex fuel sending unit located behind the passenger-side fenderwell. While the option shown here, mounted directly to the rail, was appealing, once we put a gauge on the regulator we became concerned about hood clearance.
16. After trying a few things we figured out we couldn’t mount the regulator directly to the fuel rail, so we formulated another idea. Tray carefully measured the bolt holes for both the throttle body and the factory mounting bracket that came with the regulator and fabricated a bracket that mounted the regulator to the two driver-side screws that hold the throttle body in place. In the final configuration, we mounted the regulator on its bracket just a little forward of the driver-side fuel rail, replacing a short aluminum hardline Tray had fabricated with an über-short length of braided hose between two straight hose ends. This gave us just a bit of flexibility so we could line up the regulator with the return from the other fuel rail and the return going out of the bottom of the regulator headed to the flex fuel sending unit.
17. The FAST XFI computer we’re using has the capability to run the motor on flex fuel, and does so by using an expensive GM flex fuel sending unit. But, we wanted the E85 option, so we purchased the sending unit, the wiring pigtail, and the push-lock-to-AN adapter fittings.
18. We mounted the flex fuel sending unit to the inner fenderwell just behind where the fender-vent attaches. Fortunately, a few of the holes already lined up, so there wasn’t much drilling. After everything was in place and thread-locked, we shortened the protruding screws and painted it black.
19. The plumbing for the flex fuel sending unit was mocked up using hardware we had on hand, and we carefully bent aluminum hardline into the correct shape. Since the inlet and outlet both used push lock fittings, we used adaptors so we could connect them to the AN fittings used in the rest of the system.
20. Here you can see the aluminum lines we used as templates and the finished stainless lines. We could have used the aluminum lines, but we liked the higher safety margin of the stainless lines.
21. Behold the finished stainless hard lines. The “in” line to the “y” at the top of the flex fuel assembly is the hose that comes down from the regulator mounted at the front of the engine, while the “out” line at the downstream “y” goes straight down the frame rail and returns to the fuel tank.
22. Then it was time for the moment of truth. We put gas in the tank, ran the power and ground wires to a battery charger, and started looking for leaks. When dealing with fuel it’s a great idea to triple check each fitting and connection point, since a leak could ruin your whole day, or worse. vette