The SN65 is a 1965 Mustang built by Bob and Wayne Julian, and it’s the results of combining a 1965 Fastback with a 2003 Mustang Cobra. This time, we followed the Julains as they replaced the stock supercharger with an upgraded unit from Whipple.
The SN65 is a 1965 Mustang built by Bob and Wayne Julian, and it’s the results of combining a 1965 Fastback with a 2003 Mustang Cobra. This time, we followed the Julains as they replaced the stock supercharger with an upgraded unit from Whipple.
The stock Roots type supercharger in the 2003 Cobra’s 4.6 liter dual overhead cam V8 is a powerful, reliable unit capable of making 12-13 pounds of boost from the factory. However, the Julians discovered that a Whipple Twin Screw supercharger would bolt in place of the stock unit, and with the correct pulley installed, would produce upwards of 17 pounds of boost. More boost = more power.
The first stage to this upgrade is to remove the stock blower assembly. The Julians removed all the throttle cable linkage, the throttle body, belt, wiring, and miscelaenous items found on the top of the engine.
The supercharger assembly contains an intercooler mounted below the blower, and the whole assembly comes out together. Be careful; it’s not light.
Once on the bench, the factory blower is stripped of the fuel injectors, idle control solenoid, and intercooler assembly. These are all transferred to the new Whipple W140 Twin Screw unit.
The Whipple is called a Twin Screw because of its design. The Original blower features vanes inside a case that rotate by the force of the belt. The Whipple is also belt driven, but the vanes resemble two screwes threaded together rather than two paddles like the factory unit. These twin vanes compress the air in the front of the housing, then send the compressed air down the assembly and finally down into the engine. Whipple claims their blower design generates less heat and is more efficient than the factory unit.
A smaller pulley is installed to spin faster and generate a higher boost level. Once all the goodies are transferred to the new blower and the new, larger 60 lb./hr. Fuel Injectors are in place, the new assembly can be lowered back into the car. Wayne installs new intake manifold gaskets. Although the gasket design is reusable, Wayne felt that any gasket designed to contain increased intake pressure should be replaced.
One of the items removed initially was the Exhaust Gas Recirculation (EGR) valve and tubing. The EGR allows for a percentage of exhaust gasses to be recirculated back into the intake air to reduce pollution and to capitalize on unburned fuel in the exhaust. Shown here is the EGR tube… this was the big hang-up on this installation. The EGR tube is rigid, it requires special attention when reinstalling. The Julians ended up attaching the EGR tube to the EGR valve, then attaching the valve to the blower assembly with the blower loose on the engine. It’s really difficult to align the tube to the valve with the blower bolted down solid.
In addition to the supercharger, the Whipple kit requires some additional components which they supply. These include replacement gaskets, the larger Fuel Injectors and harness extensions, a recalibrated Mass Air Flow meter, a new belt, and some smaller gaskets. After the install, the car needs to be re-tuned to match the new parts.
On the Dyno at Speed, Inc., the SN65 was ready to be Tuned by the knowledgeable hand of “The Flyin’ Hawaiian”, Bob Kurgan of Kurgan Motorsports. Kurgan used software from Superchips Custom Tuning (SCT) to dial in the air/fuel ratio, timing, and other settings on the Cobra engine to make the safest and highest level of power.
The first runs netted 523 hp and 454 ft. lbs. of torque. Kurgan began his massage work and soon the numbers and the air / fuel ratio came around. The best of the day was 537 hp and 502 ft. lbs., with a clean air / fuel curve. There’s probably more power in the car, but Kurgan noted the engine was getting pretty warm after 6 consecutive pulls.
Overall, the Julians are happy with the Whipple install on the SN65. Their goal was 550 rear wheel horsepower, and they’re not far from it. Heck, better weather conditions and a cooler blower may make that happen. Now they’re off to go thrash the heck out of the car at some planned road course events. Good, we say. That’s what the car is for!
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