The Moss Motors supercharger kit for the MGB was ranked among the twenty most significant achievements of the year by Grass Roots Motorsports Magazine in December 2003. We drove the MGB owned and modified by Mr. Carl Heideman, Eclectic Motorworks LLC, Holland, Michigan. We decided it was the most significant MG achievement in our last twenty years, and promptly (as in when we gave the keys back to Carl) ordered one. Before the order was accepted, however, we had to determine and submit the compression, which tested at 128/130/135/132 psi. These values indicated to Carl that we needed the pulleys that would give an eight psi boost. Less boost is recommended for higher compression engines.

The kit came to us shortly after. The supercharger unit itself was impressive enough to bring out after a dinner with non-MG friends. They were amazed, but having a big, shiny motor part in the living room may have been part of the amazement to them, even though they have visited us often enough before.

The kit consists of an Eaton M45 supercharger (a Roots-type dual-rotor twin-lobe unit), a new alternator, a new water pump (cast iron body-type), serpentine idler pulleys, a serpentine pulley to replace the harmonic damper, the serpentine belt, a K&N air filter and all the hoses, fuel filter, cables, nuts, bolts and thread locker needed. There was no guess work required, thanks to a very detailed 28-page instruction manual, which we read about three times before starting the project.

The supercharger module is pre-assembled by Moss on to a custom intake manifold and includes a new SU HIF44 carburetter. The throat on this carburetter measures just under one and seven-eighths inches. Otherwise, it is simply a big SU HIF4.

Installation is within anyone's ability if they have done maintenance and repair on an MG engine before: install the new alternator (the old fan must be reused), install the new water pump, install the new crank pulley (the engine must be loosened from the motor mounts and jacked up until the gearbox bell housing touches the tunnel, and mount the supercharger. We thought there would be a problem with removing the old crank pulley, but it came right off with a home-made puller (please see the photo).

Prising off the old harmonic damper.
A garage door pulley hanger was bent and bolted to the damper. The pry bar must go against the crossmember, NOT THE STEERING RACK

We changed the oil and filter, of course, before starting the engine the first time. The engine ran quite well with the carburetter settings that had been factory adjusted. We set the ignition timing as recommended, and began driving the car. We found that the carburetter float valve leaked a little, causing flooding sometimes on idle and occasionally difficult hot restarts. A new float valve arrived from Joe Curto, courtesy of Eclectic Motors LLC, and all has been fine.

Driving the car is astonishingly simple. Unless the throttle is opened abruptly and far, the car acts like a normal MGB. But if the accelerator pedal is depressed about halfway at 2000 rpm, the tachometer very shortly swings to the right. The most obvious indication that the supercharger is working its magic is the geary whine coming from immediately in front of the steering wheel.

The supercharger module installed. An additional return spring was added to the choke linkage to assure full-off operation.