In addition to providing an increase in horsepower and better performance a supercharger can also produce a smoother running engine eliminating loss of power at high altitudes and high temperature. Also due to the increased atomisation of the fuel the car is easier to start particularly in the cold.
Adding a Judson to an old over tired engine in poor condition would be detrimental to performance. Judson always advised that the stock engine must be in good condition, well run in and properly tuned. Judson also insisted that their superchargers should only be used on the engines that they were designed for and not be adapted to fit a different vehicle. Included in a Judson kit was a carburettor jet to furnish the correct mixture required and notes regarding exact ignition settings alongside the relevant pulley belts and brackets required for installation.
To Purchase a Judson today would cost upwards of £500 for a second hand kit to between £1000-£1500 for a complete boxed item. If you are looking to buy a fully restored item from a Judson restoration expert then you will expect to pay between $1500 - $1800 dollars for a VW kit. If buying a fully restored kit is too rich for your blood then what do you need to know to purchase a kit second hand. Firstly if buying over the internet you need good quality photos of all of the components and a full listing of all items included in the sale to ensure that there are no components missing or replaced with non genuine parts. One of the major considerations when purchasing a supercharger is the internal condition of the body. The profile of the four slots that house the vanes in the rotor is most important - they should be parallel when viewed from the ends with a minimum of flaring due to age related wear. If the vanes are damaged you will be looking around $80 to replace and the rotor itself would be around $400. For a VW Beetle the supercharger kit included the following items : Supercharger body, double crankshaft pulley, alloy air cleaner assembly, generator flange, supercharger support, 2 drive belts, oiler including 2 support brackets 4 screws and oil line, 3 main gaskets for the blower to inlet manifold, throttle rod, carburettor control arm, 2 carburettor studs, 2 supercharger studs, no. 140 carburettor jet, fuel pump spring, choke wire, windshield decal and instruction leaflet.
So there you have it the Judson supercharger. This is a fantastic period accessory which will give you that added horsepower often needed when driving your vintage VW on the modern motorways. This accessory is becoming very popular again on the vintage show circuit but bear in mind that like your 30bhp engine you will need to give it love and attention. The Judson supercharger is a vintage piece in itself and you can not walk into your local VW spares business and pick up parts off of the shelf. For further information on installation and running a Judson supercharger check out the Judson register on the Internet at
http://vwjudsonregister.tripod.com/. The old website is now closed as of late 2015, the link supplied here will lead you to the new sources of information on the Judson supercharger.