Alan,
Forgive me but I am getting older and cannot remember. Does your
car have the mechanical tach or the electronic one?
If the engine sounds like it is maintaining constant revs, then
it may be that a) if mechanical tach, it could be that the cable
has a kink in it, or the tach itself is binding at those revs, or
b) if electronic it could be either the sending or receiving
unit is acting up. It could also be the pertronix ignition is
causing the problem. (electronic tach)
Basically, unless the engine is missing at that speed, I don't
think that you need to go through and change plugs, etc.
Doug
--
Doug Mitchell
mailto:dbmitch@peoplepc.com
'73 Spitfire 1500
'73 Stag
-----Original Message-----
From: ralemen@cableone.net [mailto:ralemen@cableone.net]
Sent: Monday, January 28, 2002 10:18 AM
To: spitfires@autox.team.net
Subject: rev counter erratic
I have as told in past emails got my new twin SUs etc done. Yesterday on a run
( about 40 miles) I noticed that the rev counter was erratic even although the
engine speed was nice and constant and it felt fine. At about 3000 rpm when
running it jumps around a bit. Fine under 2500 rpm. Worst on deceleration at
that speed. So cruising at 70mph it was really bad taking my foot off the
accelerator pedal. Car really did feal smooth. This has all new electronics
about a year or so ago. Running Pertronix Ignition, Crane PS20 ( 40kv
ballasted) coil, 42 thou gaps, standard Champion copper plugs. It got a now
dizzy cap and rotor at the time. Most is has done is a thousand miles or so
max in the that time. Any ideas apart from stripping it all out, cleaning
contacts etc. Or could it be the dizzy? Vacuum advance mechanism works fine as
far as I can tell from revious checks.
Also is it worth putting in better plugs. I was thinking of platinum again.
Alan
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