The Maximum Overdrive concept started at the winter '04 NCRS meet at OldTown in Kissimmee, Florida. Jerry Pitt, during a previous conversationconcerning improvements for the early Corvettes, mentioned the Keislerfive-speed overdrive-equipped Corvette. He had driven the car and feltthe OD transmission was a major improvement over the OE Munciefour-speed.
We heard Keisler was modifying the Tremec transmission for installationinto early Corvettes, and it sounded like a smart move. Tremec suppliesthe transmission for the C5. Shifting is easy and has proven reliablewith high-torque applications. We wanted to drive the car to feel thetransmission and hear the change in noise level from the reduced rpm.
The original numbers-matching...
The original numbers-matching engine was in fair shape with many correctparts. There was a mix of correct replacement parts along with someinteresting quick fixes. The plastic fuel filter and rubber hose couldbe dangerous. Even a small fire can burn through the plastic fuelfilter. The engine ran OK but was a bit fuel rich at low engine speeds.
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 theright choice. It shifted smoothly with positive feel. Highway cruise rpmwas 2,200 at 70 mph and the sound level from the small-blockside-pipe-equipped Corvette was certainly livable.
After the road test, we discussed a possible engine change to complementthe OD transmission. Shafi wanted to bring his '65 Corvette coupe intothe 21st century. We discussed possibilities and other enhancements thatwould be necessary. We wanted good fuel mileage and power with hightorque to eliminate excessive shifting and lugging.
The Ram Jet looked at home...
The Ram Jet looked at home in the '65 engine bay. A paint stick was usedto check hood clearance with the original small-block hood. There washalf an inch between the intake and hood at its closest point. GM placedthe engine closer to the passenger side of the frame, so throttle-bodyclearance was an issue. The hood would not close because of the throttlebody.
We compiled a list of pieces that would work well together along withpossible options. We met Shafi at the Knoxville Corvette Expo; he likedour plan and thought it would be a good idea to have the new enginefeeding on cold, cowl-inducted air.
We decided on a serpentine-belt accessory drive system with Vintage A/Cfor cockpit cooling. The engine would be the 383ZZ425 unit (383 ci, 425hp) from GM Performance Parts. We also had a lengthy punch list ofunderhood and interior items that required attention. After a call to asome friends at GM and a few conference calls with Shafi, we decided touse the GM 350 Ram Jet electronic-fuel-injection Performance Parts crateengine. Even though the horsepower numbers were lower than the ZZ425engine, the torque number was 400 lb-ft at 3,500 rpm, which would beenjoyable shifting through the gears.
The 350 Ram Jet achieves high torque numbers with the help of the largeintake plenum feeding Vortec cylinder heads and a new MEFI IV enginecontroller (computer) handling fuel and spark delivery.
Removing the throttle body...
Removing the throttle body allowed closure of the small-block hood. Withmodification of the X-frame at the location of the throttle body andthrottle lever, the small-block hood could be used. Keep in mind, eachfitment situation is different depending on body-mount condition andbody shims used during assembly.
The MEFI IV engine controller uses a heated oxygen sensor for quickclosed-loop fuel control. All the engine sensors are reliable GM pieceswith weatherproof sealing. The MEFI IV also uses a knock sensor forengine- detonation protection. The controller is small, compact, and athome in the engine compartment.
The GM 350 Ram Jet was the best choice for other reasons. It's acomplete package, including wiring harness and computer, requiring onlyfour wires to connect to the existing mid-year harness. We could use theoriginal ignition shielding and all hardware. Plus, the 350ci Ram Jetwould be easier to cool considering the limited radiator area and addedheat load from the A/C system. Best of all, the engine would look likethe sought-after early Ram Jet mechanical fuelie engine.
The Ram Jet 350 would fit in the early Corvette, but the stocksmall-block hood would require minor surgery to the inner X-frame toclear the throttle body without any external modifications. The stockhood would also allow use of the air filter that came with thePerformance Parts engine.
We replaced the original Ram...
We replaced the original Ram Jet oil pan with an '86-'90 L98 Corvetteoil pan for proper ground clearance. The L98 pan is available from GMPerformance Parts under PN 10055765. A new oil-pump pickup is requiredfor the L98 oil pan. The Ram Jet oil pump uses a high-flow 3/4-inch tubepickup assembly, PN 12550106. The early Corvette oil pans aren'tavailable, so the L98 pan is a nice touch.
Since we had decided on the '67 big-block hood for cold air and the lookof the Stinger, it was installed for a trial fit. After installing thehood and engine, the big-block hood had enough clearance for thethrottle body without any modifications. The hood also allowed plenty ofclearance for fresh-air ducting. We decided to use the big-block hoodwith cowl intake air provision.
Next it was time to accessorize. There were a few options for theserpentine-belt drive system. We liked the Vintage Air A/C system fromprevious installations, and it seemed natural to use the Vintage AirFrontrunner accessory drive system and A/C system for a total
With a coat of Chevy Orange,...
With a coat of Chevy Orange, the Ram Jet looked more like itspredecessor. The ram's horn manifolds bolted right up so the factoryside exhaust could be used. We installed the plug-wire shields toprevent damage. We used all the original plug-wire brackets andretainers to allow radio shielding installation.
package. The Frontrunner pieces were well finished and thought out. Theyuse an OE-style belt tensioner that tightens the belt with engine-rpmtorque load.
Next was an efficient aluminum radiator and electric fan that couldhandle extended idle periods with the A/C on. Be Cool Radiators had adirect-fit module that included an aluminum radiator, a high-flow2,800-cfm electric cooling fan, a wiring kit with temperature switch, aradiator cap, and an overflow reservoir.
We had to consider the 350 Ram Jet fuel system requirements up frontbecause of the electronic fuel injection. We needed an electric fuelpump with a 5/16-inch fuel-return line and additional wiring. We firstthought about modifying the original fuel-sending unit, but with timeconstraints and the original fuel tank's condition, a custom tank withall the latest technology was considered.
The engine is in place and...
The engine is in place and ready for connections. Because of the VintageAir Frontrunner design, the engine could be installed with allcomponents in place. Notice the plug wires changed color. In our hasteto assemble, we forgot the Ram Jet engine comes with a set of GMPP underexhaust manifold plug wires. So we installed the GMPP wires and a GMPPcoil to fit in the original coil bracket. This required modifications ofthe wire harness.
We did some research and found Rick's Hot Rod Shop that listed a customfuel tank for the '65 Corvette coupe. Rick and Hector at RHR wereknowledgeable and easy to work with. Hector said they could put togethera 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 originallocation with a few minor modifications, which saved considerable time.
To ensure the new components would be happy and work optimally, weinstalled Lectric Limited wire harnesses from front to rear.Unfortunately, wire harnesses are often overlooked. After 40 years, theinsulation and wire becomes brittle and can cause low voltage to keycomponents, which eventually causes damage. Dash gauges will also beaffected by the high-resistance wiring.
The Ram Jet looked correct...
The Ram Jet looked correct from the bottom side. Notice the oil-filterarea--there are two coolant hoses that connect an L98 oil cooler. Thealuminum tube that runs along the oil-pan rail is connected to theheater hoses. The L98 oil cooler is a simple addition that lowers theoil temperature about 25 degrees.
Next was the dash, and we had a problem with the early mechanicaltachometer. It needed electronic movement to work with the Ram Jetengine. Instrument Services in Monteagle, Tennessee, confirmed theconversion could be done without permanent changes. The originaltachometer mechanism could be restored to mechanical operation ifnecessary. Instrument Services converted the fuel gauge to use a0-90-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 KnochInterior Components. The carpet, dash, and glovebox door were in faircondition, but looked rough with the new components. The paintedinterior trim pieces were fair with scrapes and scratches; but we hadtime--why not finish the interior?
We fabricated this cowl induction...
We fabricated this cowl induction hood insert. The hood will receivefinishing touches at a local body shop. It's designed to seal to anairbox that surrounds the air filter.
Some pieces required outside restoration. The hood and headlight bucketswould be replaced along with painting the front half of the car, whichadded more aggravation to the equation. But there was no extra time. Toget the car finished by the Hot Rod Power Tour, we had to stay onschedule.
We hauled the '65 back from Knoxville. In retrospect, the projectstopped just short of a major restoration in record time. In futureissues, we'll go into detail about the RHR fuel tank, fuel-systemplumbing, Vintage air A/C, Frontrunner, BeCool radiator module, andinterior harnesses and gauge installation.