Smiths Rev counter wiring? Positive or negative earth?

[rolesyboy]

Hi. I have an old Smiths 80mm rev counter (think it came off a Lotus) and ithas the code RVI 1003/00.
Questions:
1)How can I tell if it is meant for a positive or negative earth car? I think positive as it has a plastic block on the reverse with a wire looped through it..
2) How do i wire it up. It has a bank of 3 terminals, one of which is a red plastic twirly thing (technical term) and the other two habe brass nuts on them. In addition there is the plastic block with loop of wire I mentioned.
Many thanks. Mark

[rolesyboy]

Also can I use this set up with \Metro electronic ignition? Cheers

[1071bob]

Have a look here:-
http://mk1-performance-conversions.co.u ... trical.htm

[rolesyboy]

Thanks Bob. I had already looked at this but I don't understand the bit about Impulse lead and where to put it. Which coil terminal does the black marker side go to (+ve or -ve?)and where does the other end attach to? Cheers. Mark

[1071bob]

Not sure if you looked in the 'care of instruments' section as there is a better wiring diagram there. From memory these tachos don't like electronic ignition.

[mk1]

If you connect your tacho to electronic ignition it will

blow up.

[greyghost]

i've got an impulse tach hooked up to the petrozix points replacement and it's working fine.
it is how-ever just an "hall-effect" switch, which means that it is "fancy" points.

i wouldn't connect it to any other electronic ignition system, cause you will Kill it.