The Maximum Overdrive concept started at the winter '04 NCRS meet at Old Town in Kissimmee, Florida. Jerry Pitt, during a previous conversation concerning improvements for the early Corvettes, mentioned the Keisler five-speed overdrive-equipped Corvette. He had driven the car and felt the OD transmission was a major improvement over the OE Muncie four-speed.
We heard Keisler was modifying the Tremec transmission for installation into early Corvettes, and it sounded like a smart move. Tremec supplies the transmission for the C5. Shifting is easy and has proven reliable with high-torque applications. We wanted to drive the car to feel the transmission and hear the change in noise level from the reduced rpm.
We met Shafi Keisler at the Old Town show and, after a short discussion, were handed the keys to the '65. The road test proved the Tremec was the right choice. It shifted smoothly with positive feel. Highway cruise rpm was 2,200 at 70 mph and the sound level from the small-block side-pipe-equipped Corvette was certainly livable.
After the road test, we discussed a possible engine change to complement the OD transmission. Shafi wanted to bring his '65 Corvette coupe into the 21st century. We discussed possibilities and other enhancements that would be necessary. We wanted good fuel mileage and power with high torque to eliminate excessive shifting and lugging.
We compiled a list of pieces that would work well together along with possible options. We met Shafi at the Knoxville Corvette Expo; he liked our plan and thought it would be a good idea to have the new engine feeding on cold, cowl-inducted air.
We decided on a serpentine-belt accessory drive system with Vintage A/C for cockpit cooling. The engine would be the 383ZZ425 unit (383 ci, 425 hp) from GM Performance Parts. We also had a lengthy punch list of underhood and interior items that required attention. After a call to a some friends at GM and a few conference calls with Shafi, we decided to use the GM 350 Ram Jet electronic-fuel-injection Performance Parts crate engine. Even though the horsepower numbers were lower than the ZZ425 engine, the torque number was 400 lb-ft at 3,500 rpm, which would be enjoyable shifting through the gears.
The 350 Ram Jet achieves high torque numbers with the help of the large intake plenum feeding Vortec cylinder heads and a new MEFI IV engine controller (computer) handling fuel and spark delivery.
The MEFI IV engine controller uses a heated oxygen sensor for quick closed-loop fuel control. All the engine sensors are reliable GM pieces with weatherproof sealing. The MEFI IV also uses a knock sensor for engine detonation protection. The controller is small, compact, and at home in the engine compartment.
The GM 350 Ram Jet was the best choice for other reasons. It's a complete package, including wiring harness and computer, requiring only four wires to connect to the existing mid-year harness. We could use the original ignition shielding and all hardware. Plus, the 350ci Ram Jet would be easier to cool considering the limited radiator area and added heat load from the A/C system. Best of all, the engine would look like the sought-after early Ram Jet mechanical fuelie engine.
The Ram Jet 350 would fit in the early Corvette, but the stock small-block hood would require minor surgery to the inner X-frame to clear the throttle body without any external modifications. The stock hood would also allow use of the air filter that came with the Performance Parts engine.
Since we had decided on the '67 big-block hood for cold air and the look of the Stinger, it was installed for a trial fit. After installing the hood and engine, the big-block hood had enough clearance for the throttle body without any modifications. The hood also allowed plenty of clearance for fresh-air ducting. We decided to use the big-block hood with cowl intake air provision.
Next it was time to accessorize. There were a few options for the serpentine-belt drive system. We liked the Vintage Air A/C system from previous installations, and it seemed natural to use the Vintage Air Frontrunner accessory drive system and A/C system for a total package. The Frontrunner pieces were well finished and thought out. They use an OE-style belt tensioner that tightens the belt with engine-rpm torque load.
Next was an efficient aluminum radiator and electric fan that could handle extended idle periods with the A/C on. Be Cool Radiators had a direct-fit module that included an aluminum radiator, a high-flow 2,800-cfm electric cooling fan, a wiring kit with temperature switch, a radiator cap, and an overflow reservoir.
We had to consider the 350 Ram Jet fuel system requirements up front because of the electronic fuel injection. We needed an electric fuel pump with a 51/416-inch fuel-return line and additional wiring. We first thought about modifying the original fuel-sending unit, but with time constraints and the original fuel tank's condition, a custom tank with all the latest technology was considered.
We did some research and found Rick's Hot Rod Shop that listed a custom fuel tank for the '65 Corvette coupe. Rick and Hector at RHR were knowledgeable and easy to work with. Hector said they could put together a stainless steel tank with fuel pump and sending unit in a few weeks. The tank came in on time, and was a work of art. It fit in the original location with a few minor modifications, which saved considerable time.
To ensure the new components would be happy and work optimally, we installed Lectric Limited wire harnesses from front to rear. Unfortunately, wire harnesses are often overlooked. After 40 years, the insulation and wire becomes brittle and can cause low voltage to key components, which eventually causes damage. Dash gauges will also be affected by the high-resistance wiring.
Next was the dash, and we had a problem with the early mechanical tachometer. It needed electronic movement to work with the Ram Jet engine. Instrument Services in Monteagle, Tennessee, confirmed the conversion could be done without permanent changes. The original tachometer mechanism could be restored to mechanical operation if necessary. Instrument Services converted the fuel gauge to use a 0-90-ohm fuel-sending unit, which was in the new fuel tank.
We decided an interior facelift was necessary. The seats, door panels, and quarter-panels were installed at the Knoxville Expo by Al Knoch Interior Components. The carpet, dash, and glovebox door were in fair condition, but looked rough with the new components. The painted interior trim pieces were fair with scrapes and scratches; but we had time-why not finish the interior?
Some pieces required outside restoration. The hood and headlight buckets would be replaced along with painting the front half of the car, which added more aggravation to the equation. But there was no extra time. To get the car finished by the Hot Rod Power Tour, we had to stay on schedule.
We hauled the '65 back from Knoxville. In retrospect, the project stopped just short of a major restoration in record time. In future issues, we'll go into detail about the RHR fuel tank, fuel-system plumbing, Vintage air A/C, Frontrunner, BeCool radiator module, and interior harnesses and gauge installation.