Tom Wilson
December 1, 2004
Looking as if it grew there, the Kenne Bell supercharger for Mach 1s and '99-'01 Cobras is a great fit to these exciting Four-Valve engines, as long as boost is kept at 9 pounds or less. More boost requires a prepped short-block.

When Ford bolted the Eaton Roots-type supercharger on the '03 Mustang Cobra, the '99 and '01 Cobra owners developed blower envy faster than a top fueler pegs a boost gauge. And why not? The late-model Cobra is a real battlewagon, and it has been the performance benchmark for Mustangers since the first one rolled out of a showroom.

Thus was born the current climate where early Four-Valve Cobra owners are quick to add forced induction, seemingly in an effort to keep up with their '03-'04 counterparts. Adding a blower does make a great engine, as the multivalve 4.6 is eager to handle huge air volumes at entertaining rpm levels. For years, the workable solution has been to add a centrifugal supercharger, which works wonders on the upper midrange and truly sparkles at the top end.

But now Kenne Bell has worked up a kit for the '99 and '01 Cobra (as well as the similar Mach 1) engines using an Autorotor Twin-Screw style supercharger. Broadly speaking, the new kit is Kenne Bell's existing '03 Cobra kit (see "Snake Bit Hit," Mar. '03, p. 71) modified to fit the earlier cars. Of course, the '03 Kenne Bell kit benefits from the base car already having a supercharger, so the '99-'01 version includes many more pieces-and yes, some dollars to the bottom line-to support the supercharger.

As is the Roots-type blower on the '03 Cobra, the Lysholm-screw blower of Kenne Bell's is a positive-displacement device, meaning it delivers big boost from just off-idle all the way to redline. That, in turn, means the Kenne Bell blower pumps out the same sort of muscular power as the '03 Cobra. But thanks to the greatly increased efficiency of the Lysholm screw, the Kenne Bell blower puts out much more power than the Eaton-built Roots-type blower. It would seem to be the best solution for those looking to make late-model Cobra showroom power from earlier cars.

Our subject engine was outfitted with a full suite of Kenne Bell options, including a 90mm mass airflow sensor and intercooling as indicated by the air-to-water system's fill tank.

If there is a fly in this ointment, it would be the internal specifications of the '99-'01 Cobras. These engines do not use the forged pistons and studly H-beam connecting rods or the iron block of the current Cobra. This means careful attention to detonation control is absolutely mandatory, as the mechanical strength reserve is less with the earlier Cobra engines. Furthermore, Kenne Bell cites a 9-pound boost limit on the stock Cobra and Mach 1 engines to avoid mayhem simply from increased mech-anical stresses. Any more boost requires a prepped short-block with the heavy-duty forgings.

One bright spot shines for early Four-Valve Cobra owners compared to their '03 brothers: a knock sensor. Located on the block, the knock sensor pulls ignition timing when it "hears" the vibration caused by knock or ping. It's a handy device, to say the least, but it's still not the sort of gadget you want to stake your Four-Valve's life on. There's no substitute for an adequate fuel system and intelligent engine-management software.

In fact, avoiding detonation is all about controlling combustion temperature, and the two main tools for that job are not getting overly excited with the ignition timing and supplying plenty of fuel at all times. Kenne Bell controls timing with its electronic chip. Improving the fuel system is done with the the company's Boost-A-Pump electronic augmenter on the base kit, and larger in-tank pumps and the Boost-A-Pump with some of the higher output kits. Eventually, when getting into the higher-dollar, high-output systems, Kenne Bell heavily recommends pitching all the extra pumps and simply updating to the '03 Cobra fuel system. That means purchasing an '03 Cobra fuel tank and its two in-tank fuel pumps. This gives unquestioned fuel delivery with OEM levels of quiet and fit. The parts required are as follows.