I have a smiths 4 cyl neg earth
number PVI 2413/00
i think it was out of an early ford Cortina

does anyone know which wire goes where, I have included a photo

I'm using a standard coil, not an electronic one

[Edited on 16/5/08 by peterparsons]
Rescued attachment tacho.JPG

If its out of an early Tina, there is an inductive loop missing in your pic. it goes where the knurled nut is on the right. This loop-just two coils- is what picks up the low tension pulses on the + side of the coil. The spade connector is ign + and the threaded post is ground.

[Edited on 16/5/08 by Fatgadget]

Note that the early inductive tacho's generaly won't work with electronic ignition.

Alternatively...

Isnt the interweb wonderful?

[Edited on 16/5/08 by Fatgadget]