1965 Chevrolet Corvette EFI System - EFI Incognito

Designing and building a supercharger system for my '65 fuelie convertible was certainly a challenge, but it was perfect therapy for a new retiree. In addition, having a story about the job published in the Feb. '04 issue of VETTE was most rewarding.

It took several months to complete the fine-tuning on the system. Using larger nozzles, changing the economy and power stops, and overboring the choke-diffuser cone 0.200 inch corrected most of the problems. Moving the air filter near the driver-side fender vents to isolate it from the hot air under the hood improved idle consistency during summer months.

However, as a typical gearhead, I am always looking for a new challenge when it comes to my favorite hobby. Several months after completing the project, I heard that Craig Railsback, at Blower Drive Service (BDS), was working on an EFI system that utilized the original Rochester fuel-injection plenum and cover and would fit under the hood of a '65 Corvette. I called Craig and made an appointment to look at his unique design. After arriving at BDS, it didn't take long for Craig to convince me that building an EFI system using a Rochester plenum would be an ideal project in my continuing quest to squeeze more horsepower and torque from the original 327.

Several weeks later, I decided to proceed with the project and ordered the major parts from BDS. Some of the components are available from speed shops, while others are difficult to locate because they are used exclusively by Mercury Marine. Needless to say, any part used for marine application is very expensive. (A list of parts used may be found later in this article.)

While waiting for the parts to arrive, I started searching for a '65 Rochester FI plenum. After several months, I found an N.O.S. GM service part that was originally a sand-casting. It had been sanded smooth but didn't look like an original plenum. I had it restored in a vibratory until the surface looked just right.

Very few modifications were needed on the plenum. The original nozzle-block bores needed to be overbored to accept the new injectors' larger O-rings. Several surfaces also had to be milled flat to mate with other components that would be bolted to the plenum for support. The new 45-pound injectors were secured with custom spacers using the 1/4-inch, -20 thread that held the original nozzle blocks in place.

After the parts arrived from BDS, it was time to start fitting the new components to the Rochester plenum. As a former machinist, I especially looked forward to this aspect of the project. The first and most important part involved the fuel pump and reservoir that would replace the Rochester fuel meter. This part is called a vapor separator tank (VST) and was used on MerCruiser 496 and 502 engines several years ago. The VST was selected by Craig Railsback because it contains a traditional fuel reservoir and an electric fuel pump in the same housing. This design eliminates the need to run a return fuel line to the tank.

The trick was getting the VST to fit in the space available and under the hood. The first step involved cutting the original mounting brackets off the bottom of the VST, allowing it to be mounted as low as possible to the right-hand valve cover. Fortunately, the VST has additional mounting surfaces. I designed and machined a bracket, which I bolted to the bottom of plenum and to the side of the VST at a 6-degree angle. The angle allows for hood clearance and an inlet fuel-banjo fitting. Another bracket was added about 2-inches higher to stabilize the VST to the plenum. Hood clearance ended up being 5/16 inch.

The next major component to adapt to the plenum was the throttle body. Fortunately, the unit's 75mm butterfly is very close in size to the 3 1/8-inch opening in the plenum. Because the bolt patterns on the plenum and throttle body are different, I machined a 5/16-inch adapter plate that bolts the throttle body in the exact location of the original air meter. The original bellcrank was moved back 111/44 inches on the plenum using an adapter that bolts to the original bolt location. This throttle body is made by ACDelco but is only available from Mercury Marine.