Join Date: Mar 2002
Location: Austin, TX, USA
Re: Tach trouble
I suspect the tach is toast. What I *think* happens to them is that a rectifier diode on the input breaks down and eventually fails. You might try the tach filter and see if that helps. The good news is the filter is cheap and easy to make.
IMHO, it's bettery to try the tach filter instead of suffering the fate of a failed tach. The filter dampens the energy from the coil, so if it works at all, it's better for the tach. Trouble is, the OEM and OER tachs are not precision instruments and are essentially tuned to the type of ignition they're built for (typically breaker points).
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI