The C75B Supercharger

The C75B model is the model that is suitable for the 'A' series engine although it came in a variety of casings to suit the vehicle is was going into.
Its suitable for smaller engines up to 1300cc and the casing is 7" x7" and weighs 21lbs.
The fitting instructions for the 'A' series engine is shown as being suitable for the Austin Healey Sprite, Austin A35, Morris Minor 1,000 and Austin A40.
Although the instructions relate to the overhead valve 'A' series engine and in this particular case the 948cc engine, it was however tested in 1953 in a series MM Lowlight with Chris Shorrock driving as can be seen in the photo below which makes the car a pre September 1950 which would have been fitted with the 918cc sidevalve.

I have seen the supercharger fitted to a sidevalve 918cc engine, however it also has an Alta OHV conversion fitted as well. I wonder what this car actually had fitted in its engine bay as the 803cc 'A' series engine appeared in the series II Minor from August 1952 but the series MM didn't finish until February 1953 so I don't suppose we will ever know the answer to that one.

I don't have any road test figures for the actual amount of improvement in performance for the different engine sizes, however to quote Chris Shorrock from one of his brochures from the early 60's.

'SHORROCK POWER' is the name we have given to the dramatically improved performance which you will achieve simply by bolting a Shorrock Supercharger to a modern motor engine.

The function of the Shorrock Supercharger is to feed fuel into each cylinder under equal pressure with at least a third more fuel mixture than normal. We thus achieve a similar percentage increase in effective engine capacity: for example a 1500cc engine effectively becomes a 2000cc engine.

Performance tuning usually achieves extra power at the cost of higher engine r.p.m. A Shorrock Supercharged engine on the other hand, can develop up to 50% more power than the standard motor without an increase in r.p.m.

For the 948cc engine when fitted in a Morris Minor the 0-60 comes down from the standard cars 31.4 seconds to 17.4 seconds and the top speed is increased from
72.4 m.p.h. to 86 m.p.h. which is quite a dramatic improvement and the b.h.p. goes up from the standard 38 b.h.p. to 51 b.h.p. shows why the Shorrock is still very much in demand today and commands such high prices.