Yeah, you recollection is correct. The smiths went all wonky and ceased to read or act normal. I read some of that before when I was wanting to reset a 6-cylinder unit.

I changed it out for a 2" Volvo VDO tach (installed in a smiths pod), but it also reads oddly. It seems to be about 1000 rpms off. That is, when I'm idling at what used to be 900 rpms, the tach is flat. It revs as high as 4k, which is probably about 5000 rpms (just do that for tests).

I don't get why the smiths and VDO tachs read wrong - especially since I put in a blue bosch coil from a 140. If it were a coil problem, that should have fixed it, but the problem persists. The VDO will rev normally (if off) while the smiths was stuck between 0 and 2000 rpms.

I feel reasonably confident that I know where 900-1000 is, but a proper gauge would help.

What's a decent price/brand for a tach/dwell meter? I have a cheap inductive timing light and I don't much trust it's high-quality harbor-freight engineering...


My current suspicion about the mileage is the dizzy. The only time I ran a different dizzy my mileage was doing better, but the E-gnition blew out before I could finish a tank. I can't try my vacuum advance unit since I have not vacuum fitting. My only other B18 dizzy was already converted to an electronic ignition... It's the single thing in the system that I've not changed and I've been unable to rule it out as the culprit.