[Healeys] Jumpy Speedo

[BJ8 Healeys]

Hi, Jerry -
Here is a page that gives some good info on conversion of a tach to negative ground, including some testing and repair information plus calibration:
http://www.lotus-cortina.com/electric/convert.htm

There is a plastic adjustment screw inside the tachometer case to accept a flat blade screwdriver, and I assume that it is for making corrections to the calibration.  When I had my tachometer apart for the postive to negative ground modification, I drilled a hole in the tachometer case in line with the adjustment screw.  If I ever need to do the adjustment, I won't have to take the tachometer apart to access the screw, and should be able to make the adjustment while the tach is installed and operating.  I covered the new hole with a piece of electrical tape to keep out dust.
I recently had occasion to purchase a new tachometer/dwellmeter from Sears for checking/adjusting my timing and dwell.  The Sears tach and my dash tach were exactly in agreement at 600, 1000, and 3000 RPM, so I am happy.
You should have a separate tachometer (preferably one you can trust) for comparison if you are going to mess with the calibration of your tach.

Happy Healeying!
Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC  USA

---- Jerry Costanzo <grumpyinloomis at ssctv.net> wrote: 
> Has anybody seen a similar article on tachometers?   Mine is a bit off since 
> I repaired it.  It says I idle at 1500 rpms.