Tachometer/Electronic Ignition

[Pelham West <pelhamwest@domain.elided>]

Although my tachometer has always been a bit 'shakey', after fitting the
Piranha electronic ignition it has gone completely haywire. At any
reasonable speed the needle just sits sulking at the top of the dial and
refuses to give any sort of reading. I wrote to Newtronic, who manufacture
the device, to ask for their advice but they never responded to my letter.
(yes, you have to go a long way to match the unique style of British
customer service). I looked at the Lumenition web site which is very
informative. It seems that pre-'74 cars like mine with a current (or  RVI)
tachometer can expect trouble with electronic ignition. They recommend that
the later internal electronic tachometer is fitted or the existing RVI one
converted. I have found someone who is willing to convert mine but that is
not the end of the story. Lumenition  say that a minor wiring change is
also required to the normal ignition circuit and recommend a company in
London for this work. I would prefer to have this done locally. Can anyone
who has gone down this path tell me what this minor wiring change is?

Pelham