Fitting a Judson Supercharger to a 1600 MGA

From the outset, let me say that it was not an easy fit, made all the more difficult by having a MGB Mk1 overdrive gearbox fitted to my 1961 MGA, named RIP!

Preparation of fitting the Judson Supercharger

After visiting Dominic Clancy in Switzerland and driving his MGA with Judson Supercharger fitted, I sort and bought a Judson supercharger from an Australian chap in 2005 for RIP. Not knowing exactly what the kit should entail, I arrived home with the original Judson Supercharger cardboard box full of parts. Searching the internet, I found the Judson web site and soon realized that I was missing the tappet cover with integral oiler – buggar – but also had an extra Judson Supercharger for a 1200cc VW Beetle and a glass Mystery Oiler bottle – RIPper!

A few years later, I bought another Judson Supercharger – this time on eBay – which was complete, so RIP was prepared for the operation. Out came the MGB 5 bearing motor and in went the original 1600cc motor, married to the already-installed MGB Mk1 overdrive gearbox. So far, so good.

Fitting the Judson Supercharger

The first problem I encountered was there was insufficient room between the double crank pulley and the steering rack to change a belt if one should fail, so I devised a spacer that had the effect of moving the steering rack forward 10mm.  Unfortunately, this did not allow enough room for a spanner to fit over the securing nuts so another set of spacers were made to give 12mm clearance for the belts, which now also allows a spanner to fit over the fixing nuts.

The next problem I encountered was one of the twin supercharger belts was fouling the bottom radiator hose.  I sourced another hose with a suitable tight bend in it and the problem was solved. QED.

Having an alternator fitted, aligning the belts was not straight forward but was accomplished with the help of various spacers which had to be made up.

With the radiator fan spacer in place, the fan blades just cleared the supercharger tensioner pulley. I then fitted the supplied radiator spacers to move the radiator away from the fan blades. I felt the fan was too close to the radiator fins so I made another set of spacers and doubled up the gap. Whalla! No problem. I now had a 10mm gap between the radiator fins and steel blades. Unfortunately, the motor started first try and the steel radiator blade was too tall and struck the lip of the top tank; bent; and chopped through 4 cores… Ouch!  I had checked the gap but not the height!

I removed the radiator and fan and sealed the four cores but reinstalled the radiator without the mechanical fan – I did not want to cut the radiator duck plate to move it forward another 10mm – and fitted an electric fan.

The motor with Judson Supercharger would now start and run, but the Holley carburetor needed attention beyond my capabilities, so it was down with the bonnet to visit the local Carby Specialist.  Sh1t! the bonnet would not open!  After a frustrating hour, the bonnet was released and the oiler was found to be fouling the bonnet angle strap.  It took another few days to work out the reason!  The MGB Mk1 overdrive gearbox centre mount was 25mm above the original gearbox mount, raising the rear of the motor by approximately 20mm… By this stage, I was getting desperate and simply chopped off a length of the support – easily solved! Poor RIP.

On the road with my MGA, known as RIP

I bought a vacuum/pressure gauge from the Judson web site in the hope that I would achieve most of the promised 6psi in the literature.  Unfortunately, nothing I could do would show a positive pressure beyond 2psi!  RIP still motors along quite well, but I would have liked to see at least 4psi on the gauge to feel that all the work was worth it.

A side effect of the missing mechanical radiator fan and the four blocked cores is RIP overheats under load. This means actions such as driving at speed or up long hills have to be planned well in advance to ensure the radiator temperature does not go above 230F!  Not much fun!

Obtaining a constant idle has proved near impossible. The explanation given is that with a touch of the throttle, the Holley deposits a charge of fuel into the super charger and this volume of mixture takes a while to be sucked through the motor and hence the idle stays high for an extended period before settling back to 1000rpm. Anything less than this will cause the motor to run roughly.

Would I do it again?  Probably not. The 5 bearing MGB motor with overdrive gearbox suits my kind of driving perfectly. I love driving long distances – serious distances – and the MGB motor has enough power to do everything I ask of it and more – I chose to tow a friend in a MGA when in Africa in 2008 and RIP performed splendidly!

Having said that, I am sad that I have come to this conclusion as for many years, I was really looking forward to larking around with a Judson Supercharger under the bonnet. My good friend Dan Casey explained that in the era of the MGA, the MGB option was not available and with a little more work, he is convinced the Judson would have proved its performance.  I am sure Dan is correct, but, unfortunately I have to prepare RIP for our Cape Town to Cairo and Beyond Trip to Abingdon later in 2012 so time has run out for me to pursue this option.

Dave Godwin


January 2012

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