The Shorrock

VW power + Shorrock boost on this UK drag racing bike of 1969

Christopher Shorrock had been involved in the family business in Coventry, England, for about 20 years when the decision was taken to create a supercharger kit for the Volkswagen. The Shorrock superchargers had been the nec plus ultra in supercharging all types of engines on cars, planes and boats since 1937. If there has been a company exclusively dedicated to supercharge engines in the first half of last century, the name is Shorrock. The Shorrock VW supercharger appeared after 1960 and it profited of the previous designs by Arnott and Judson when it came to adapt the C75B blower to the VW, thus creating the C75 BV, official denomination of the VW kit by Shorrock.

The C75B, an excellent piece of engineering, had been in production for some time, having sold really well as a kit for the side valve Austin A from 1955 onwards. Versions for other Austins, Ford Anglia, Hillmans, MGs and Morris were developed. In parallel, adapted C75Bs (long nose kits) were being installed on Triumphs. Vauxhalls, Spitfires, Renaults and Minis followed suit. By 1965 the Shorrock kits range covered many models, all European.

C stands for capacity, 75 for the blower rate which is 750 cm³ (cc) per rev and B means blower. The C75B is indicated for engines of up to 1300 cc  capacity.

Whilst embodying characteristics of the Arnotts (the vanes design, the vanes seals, the oiling arrangements, the side draft carb, etc) and of the Judsons (sitting on top of the intake manifold, linkage arrangements, etc) its design also produced some innovations:

a) The central intake manifold was linked by rubber hoses to the head port portions. I’m pretty sure this new design breakthrough was adopted by VW some years later when the 1600 engine was created. The aim was clearly to make a manifold that could be extended in length and, in this way, suit the different distances between ports for 1200, 1300 and 1500 VW engines. Without knowing it, Shorrock had made a versatile intake manifold easily adaptable to all sorts of cylinder head ports.

b) Because the blower was mounted bolted to the two gas pump studs, the original mechanic gas pump had to be discarded and, in its place, an electric gas pump was used. This was also an innovation that preceded the subsequent trend to install an electric gas pump when deemed convenient.

c) The only steel parts are the pulleys, the blower shaft and the vanes (plus bearings, bolts, etc). It is a so-called "full aluminium" construction, more elaborated but lighter, too.

Shorrock commercialised another supercharger, the C142B, that delivered 1420 cc per rev at 5 psi boost and was indicated for engine capacities of up to 2000 cc. Too bulky, this unit was installed mostly in Rover and Ford cars.

This Shorrock c142b blows from twin carbs into a big displacement engine

And now you, air-cooled VW enthusiast, may quite rightly ask: and what’s all the fuzz about the Shorrock ?

The answer is twofold:

Firstly, this is because Shorrock is the Rolls-Royce of the superchargers: casing, rotor, endplates, manifold and pedestal cast from aluminium gives a generally light clean-looking unit still displacing a generous amount. All threads are BST and all measurements imperial. Detailing in its finishing and quietness of operation deserved the Shorrock the reputation of "classy" among VW supercharger connoisseurs. One must not forget that Darell Vittone chose a Shorrock to crown the engine of his forever famous Inch Pincher. To supply the 220 HP engine using a 1:1 pulley ratio, that Shorrock C75B unit had to be dynamically balanced and tested up to 8,000 revs. This remains a never equalled did for a car engine vane supercharger.

Secondly, this kit was commercialised in the United States by the firm EMPI. And, as you all know, when one talks EMPI one talks quality. It is not surprising, then, that the marriage Shorrock/EMPI had glamour, class, luxury, etc. In my opinion, precisely this commercial alliance based on utmost quality and excellence gave birth to a top range price list, making sales difficult precisely when the no-complex Judson competitor was filling up the shelves of the retailers with "another package of power" cardboard boxes in a vast marketing operation supported by a considerable publicity effort.

And so the story has it that Shorrock/EMPI sold very few units of the C75 BV VW kit. By the late sixties, this overseas sales fiasco backfired to the central firm in the UK, which, on its turn, was in serious cash flow problems, as sales of all different kits were deeming. Why? Because turbochargers were starting to show their ears and, at the same time, many of the British brands for which Shorrock produced superchargers (MG, Austin, Triumph, Rover, Hillman, etc.) were closing doors or were renewing their models in an effort to adapt to a new motoring era. By then, Chris Shorrock had practically retired and Sidney Allard, who had been his associate in the marketing area since 1957, carried over as exclusive distributor of the Shorrock superchargers with Allard Motor Company, Ltd., in London.

His son Alan Allard tried hard to keep afloat the Shorrock brand for approximately one decade but Shorrock Superchargers Ltd. disappeared in the seventies. The tooling, spares, some blowers, spare parts, etc. were bought by some garages in the U.K.. Allard (3rd generation) is still in business and deals currently with turbochargers.

I have tried to compile estimations of the number of Shorrock VW units produced and sold. The various sources I consulted agree that in total numbers Shorrock produced some thousands of kits, of which the C75B might account for about 10,000 units. What nobody risk to guess is how many units of the C75BV (the VW kit) were actually produced. I was told 600, someone corrected me down to half of that. Some people I asked believe that there were only a few dozens produced.  

Rare Shorrock trunnions:  their mission is to make the seal between vanes and inner drum

These pages about VW Shorrock superchargers will expand in the coming months, as I will put on-line the information I have on the subject (mounting instructions, leaflets, pictures, etc.). I will also be taking pictures of my Shorrock kits to show special features in detail. As a preview, in the following gallery I show some pictures of my kits when they were mounted on the cars of their previous owners and a couple pictures showing the inside of a Shorrock C75Bv.

See the gallery