P5B tacho

[bristolp5b]

Good evening all
Slightly out of my usual bubble , normally my classic vehicle tinkering involves 2 wheels, however here I am under a bonnet.
Hoping someone can shed some light on the coil and tachometer setup used on the P5B… I’ve been helping a friends son to do some work on his car , tidying up wiring etc, car has had luminition electronic ignition fitted, but tachometer seems to have been isolated for some reason, car also has the rather bizarre anti theft ignition supply ( my first thought was why is the coil supply wire poking out of an old speedo cable! ) I can’t see any evidence of ballast resistor so assuming original was just 12v coil and points. Two wires left over , white/grey and white/? got a wiring diagram but does not show tachometer! Any information gratefully received.

[lagain]

From vague memory there is a problem with the tacho and Luminition, it can be solved and hopefully someone else will know how. The correct wiring diagram should show the wiring for the tacho.
That is the anti theft coil, although it sounds as if it has been opened up. There is no seperate ballast resistor

[Sam Bee]

There are two versions of the tachometer, RVI and RVC; this is marked on the face of the dial in very small letters towards the bottom. Normal for P5B is the RVI. This will not work with electronic ignition. The solution is to send the tachometer off to a firm who will convert it, they send it back with instructions of how to re-wire it into circuit. Two I have used and recommend are JDO Instruments of Keithley, Yorks and Smiths Gauges, Edenbridge. The former is by far the quickest. There are of course others.