Now that its easy and popular to swap an LS V-8 into an early-model Chevy, it's no longer acceptable for the engine to remain in a plain, stock condition. There are several ways to make serious horsepower with these engines, but in doing so, it requires a completely new fuel system to feed it. For example, take a Chevrolet Performance LS3 E-rod engine, outfit it with a Kenne Bell 2.8L Mammoth twin-screw supercharger, and slide it into a '69 Camaro. It's the type of combination that Rob Green at JKR Customs in Orange, California, was currently working on, and one that gave us an opportunity to learn a few tips on how to install a modern fuel system in an early-model car.
Green says that the LS3 crate engine makes 430 hp and would normally require a factory in-tank or inline electric fuel pump that generates up to 45 psi of pressure. But adding the Kenne Bell twin-screw supercharger with larger injectors bumps up the horsepower on this engine anywhere from 785 to 800 hp. Therefore, the fuel system requirements are going to be a little different.
To upgrade the fuel system requirements for this combination, Green began by making sure the factory '69 Camaro fuel tank was in good condition and had no leaks. He decided to use an aftermarket, high-performance inline fuel pump, Holley's Billet HP fuel pump (PN 12-700). This pump features a quiet gerotor design that can be inserted in the tank or bolted externally, which is exactly what was needed in this application. Because this car now uses a four-link rear suspension, there weren't very many places where the pump could be attached. So Green elected to mount it straight onto the Camaro's trunk floorpan, just behind the driver-side rear wheelwell. This was done because the LS3's fuel inlet line is also on the driver side, and allowed a straight shot from the fuel pump to the engine's fuel rails.
The Holley pump has a black ground wire and a red power wire. The ground wire was simply attached to the frame, while the power wire was attached to the engine's computer wiring harness that primes and activates the pump when the ignition is turned on.
Green decided to use the factory fuel pickup that comes out of the Camaro's original tank, and attached an -8 steel braided hose line to it. If the Camaro was going to be drag raced every weekend, Green would have used a larger-diameter hose and fitting sizes, an AN-10, to allow for additional fuel to be available to the engine to prevent fuel starvation under hard acceleration.
For this application, the braided fuel line was routed from the Camaro's tank, and into the inlet of the Holley fuel pump. The line out of the fuel pump was routed along the driver-side subframe, and up to the engine compartment, with a Holley fuel filter located near the pump.
Connecting a braided aftermarket fuel line to an LS engine fuel rail isn't as difficult as one might think. The LS fuel inlet line has a Chevrolet Performance fuel fitting at the end of it. There are AN fitting adapters that are made to connect an AN fitting to the Chevrolet Performance–style fuel rail, but many engine builders have experienced some leaking and improper fitment. So to avoid any of this, Green used a pair of aftermarket fuel rails that have AN fittings on each end. This ensures a proper fit and that the larger injectors have a good supply of fuel at any time.
Chevrolet Performance says that the LS3 crate engine doesn't necessarily need a return line. But because the Holley pump can consistently provide as much as 80 psi of fuel, Holley recommends adding a smaller return line back to the tank. In Green's experience, with high-powered engines the fuel should enter into the driver-side fuel rail, flow over to the passenger-side fuel rail, loop back to the driver side, and then return to the tank. This keeps a consistent amount of fuel pressure and prevents fuel starvation on the side of the engine that the return line is located. To accomplish this, a single AN-6 fuel line was used to make the return line back into the Camaro's tank.
After attaching a fuel gauge to the system and starting the engine, it provided a steady 55 psi of fuel pressure. Furthermore, the Camaro starts up on the first crank of the ignition key and the fuel system provides plenty of power for this car to run on the street or strip.
While this is merely one example of how to upgrade a fuel system, when using an LS engine in an early-model muscle car, it demonstrates that its simplicity relies on using the right components to properly deliver fuel flow that allows the engine to run perfectly at idle or wide-open throttle.
1. Holley’s 12-700 billet inline fuel pump makes it easy to upgrade any LS engine swap into an early muscle car. The pump provides fuel for engines making up to 900 hp and the housing makes it easy to mount just about anywhere.
2. The fuel inlet consisted of an AN-8 hose and fitting that was connected to the top of the factory fuel pickup on this ’69 Camaro.
3. Green used some double-sided tape to position the Holley fuel pump. This allowed him to easily drill the holes for the mounting screws.
4. The flat area behind the wheelwell and near the rear subframe made for a perfect mounting position to attach the pump.
5. The -8 AN fuel line was attached to the pump and routes all the way up the driver side to the engine compartment.
6. The fuel line coming from the OEM tank was also routed into the rear of the Holley fuel pump.
7. Green made sure to secure the fuel line in various areas to keep it from potentially rubbing on any portion of the Camaro’s chassis.
8. Once the Holley pump was mounted and connected to the inlet and outlet hoses, it was time to attach the wiring.
9. The Holley pump has two wires. The red power wire attaches to the fuel pump wire that comes from the factory, or aftermarket wiring harness that controls the priming and activation of the pump.
10. The black wire is grounded to the chassis, and the wiring is secured, covered, and done.
11. The fuel inlet line attaches to an aftermarket fuel rail. It’s then routed to the fuel rail on the other side and out to a return line back into the tank.
12. With 700-plus horsepower potential from a Kenne Bell twin-screw supercharger, this ’69 Camaro has the correct fuel system that will allow the LS3 small-block to drive nicely in traffic, yet be capable of tire-blistering acceleration when needed.