The last thing we wanted was to damage the test motor so graciously loaned to us by Accufab's John Mihovetz. With the pulley change came another significant jump in torque production. The 4.6 motor now exceeded 450 lb-ft of torque from 3,600 rpm to 5,500 rpm. It is this impressive average power gain that really helps accelerate the vehicle. Sure, we all like to talk about peak numbers (with over 500 hp this motor is no slouch), but the reality is, that big smile on your face came from the immediate (and substantial) torque production offered by the twin-screw blower.
Now that we've tried the twin-screw blower, we suppose we have to give equal airtime to the centrifugal and then maybe the turbo.
Kenne Bell Supercharged Early 4.6 Four-Valve (9 Psi Vs. 12 Psi)
While we decided that 9 psi was about the limit we'd feel safe to run without an intercooler on pump gas, we couldn't just run the motor at one boost level and call it good. After topping the tank with 100-octane race fuel (remember, our tired Cobra motor was running stock compression with cast pistons), we replaced the 3-inch blower pulley with one that measured just 2.75 inches in diameter. The drop in blower pulley size increased the blower speed relative to the motor, which in turn increased the boost pressure. Increasing the boost pressure to just over 12 psi resulted in a sizable jump in power. Despite minor belt slippage with the 2.75-inch blower pulley, we were able to exceed 500 hp with a peak reading of 506 hp at 6,400 rpm. The peak torque jumped by 31 lb-ft, from 433 lb-ft to 464 lb-ft. | 
In normally aspirated trim, the '96 Four-Valve Cobra motor (with Comp XE262AH cams) produced 374 hp and 342 lb- ft of torque. | 
After installing the supercharger, the peak power jumped to 486 hp and 433 lb- ft of torque. Swapping out the 3-inch blower pulley for a 2.75-inch version upped the boost pressure to 12 psi and brought over 500 hp and 464 lb-ft of torque. |