Shorrocks - Continued

[James Mumford]

Continuing the thread on Shorrocks superchargers, I have three further questions on which I would like to seek your experiences: 1 I get a slight rumbling sound from my unit at low engine speed. I believe that this is not coming from the supercharger itself but from slight wear in the four pin dog-clutch connecting the supercharger to the drive shaft inside the nose piece. The tension on the drive belts will cause the clutch to slide slightly sideways if it can since the outer bearing by the drive pulley is self-aligning. Has anyone expeience of this problem? Is it significant or merely irritating? What should I do about it? 2 My pressure gauge, fitted to the manifold about 1in from the No4 inlet port, indicates a max pressure between +3.5 and +4lb/in2 above say 3000rpm. The unit is set up to give a boost of 6lb/in2. Is the "lost" 2lb/in2 an expected pressure drop through the carburettor and manifolds or have I got a pressure loss somewhere else? 3 I am not sure about distrubutor settings. Currently, I run with a standard distrubutor with the advance restricted as advised on the website. However, I still get a slight detonation problem and I know that some people, particularly for competition, run with a fixed distributor with the automatic advance disabled. Has anyone experience with fixed distributors for normal road use and normal fuels? If so, what advance setting is used. Any advice on the above will be gratefully received. Regards James Mumford. [Non-text portions of this message have been removed]