This MGB already has a header with free flow exhaust, fast street camshaft, lightened flywheel and Mallory dual point distributor.  The supercharger will really top this project off nicely.

Here we go into the realm of forced induction. I took a drive to Goleta to Moss Motors and came home with a supercharger. The attraction is nearly irresistible as this bolt on offers a 40% hp gain at the flywheel.

Moss doesn't offer a supercharger for for the MGB 3-main engine. According to Moss, it has a unique water pump that would be too expensive to adapt to a serpentine pulley for such  limited production. However  it is possible to install the later pump (and the provided serpentine pulley) with some modifications. The down side is that the engine block would need some minor grinding at the pump opening to make room for the newer style pump but it would improve cooling.

(top) The depth of the new pump impeller included in the Moss supercharger kit. It won't clear the block casting of a three main engine.

(2nd pic) The new gasket is the template. Metal showing on the inside of the cutout could be ground away to clear the pump impeller.

I chose not to modify the block.

  (bottom pic) The supercharger kit supplies a serpentine generator pulley (not shown) that sits 1/4" farther out than the original. Therefore, the machined water pump pulley height (left) was reduced by 1/4" to line up with the idlers and serpentine crank pulley correctly. The stock pulley is shown on the right for comparison.

The serpentine pulleys installed

No leaks and no problems but admittedly no easy task getting this kit onto a 3 main MGB. There was some anxiety about  the water pump pulley dimensions but it was all by the book after that. The new throttle cable has no provision to route securely behind the bonnet hinge securely. I used a lid switch (part#90016) harness clip from a Whirlpool direct drive washer. With minor alteration it clips the cable securely behind the hinge, preventing damage.The bonnet liner is an Ebay item. It's nitrile foam and it goes on easily and looks good too.

Initially the timing was at 13d advance per setup instructions and later adjusted to 18d.

Timing an early MGB is not easy since the timing pointer is on the bottom side of the crank pulley. With this simple tape and pointer kit (picture left), engine timing can be viewed from the top. Accurate timing is possible with an inexpensive timing light without getting under the car. This is by Jeff Schlemmer of Advanced Distributors. www.advanceddistributors.com.

The Mallory dual point distributor (which was not specifically chosen for this application) has mechanical advance and the curve is set to 16d @ 3000 rpm for a total 32d advance @ 3000 rpm. It seems to work alright and no detonation noticed yet.

The power increase really transforms the car. Low end torque is so improved that it can start from 2nd or 3rd gear with no hesitation. Shifting routines will change especially at very low speeds because second gear is much easier to use than non-synchro first gear in a slow rolling situation.

The exhaust pipe has a satisfying resonance as you ease off the throttle and there is the faint whine of a new supercharger in the background. Idle rhythm is more even and engine temperature was no different in around town traffic.

I used an Autometer Sportcomp II boost gauge and mounting cup. The cup is more versatile than the Moss offering, allowing mounting on the right side away from the indicator switch lever. Saved a few bucks too...

The Weber downdraft I was using really was lacking in the low end but it came with the MG and gave reliable service. Certainly the non-stock cam I use is a major cause but the SC literally fills  the void.

So far no regrets. Far from it actually. The investment gives a significant return in performance and fun with the coolness factor of a blower kit that was engineered for the B series MG's. Maybe they did make half a million MGB's but this mod puts a new perspective on Britain's most popular sports car.