Dave Plummer

I'd like to retain my '69 Camaro factory tach (it's probably a repro). The eRod ECM, since it's waste spark I think, fires twice as often.

They tell you to set the tach to 4-cyl mode, but I don't think I can do that with a factory style tach (there were no 4-cyl Camaros, and if there were, they'd have had their own tach part number anyway).

Is there a "box" or converter that's reasonably easy to set up that will massage the tach signal? It'd be nice if it also prevented me from needing to run a pullup resistor and all of that too!

Crf450r420

iTrader: (1)

4cyl have two sparks and signal the tach twice per revolution. 8cyl have 4 sparks and and signal the tach 4 times per revolution. GM LS gives 2 pulses instead of the 4 and your tach should read half the rpm you are actually spinning. People running Autometer tachs get and adapter from Autometer to hook to the LS, so you can likely use the same adapter to signal your older 4 pulse tach.

Dave Plummer

Thanks - I grabbed a Dakota Digital box that can convert to and from various pulses, so I should be set.