Tach way off

[mjb765]

I have been e-mailing Instrument specialties and he said that maybe the tach needs to be updated to modern electronics since it may not work properly with modern ignition. Since they calibrated it already and charged me, it would ONLY be $200 to upgrade the tach completely.

[JS29]

 Since they calibrated it already and charged me, it would ONLY be $200 to upgrade the tach completely.
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[blown motor]

Here's a shot in the dark. MSD makes a tach adaptor. Basically it's a signal amplifier. Maybe Pertronix makes one too.  Maybe there is a signal issue here rather that a calibration issue. You might be battling a weak or floating input signal. Other than using an oscilloscope to check amplitudes I dont know any other way to accuratly check the input signal to the tach. Also you can see if it's a clean signal or not ie. amplitude  differentiating or attenuating signal patterns. If the signal is dirty you can back track it with in the circuit to the source. This was one of our trouble shooting techiques we  did in my main frame gate chasing days.

I have an Autogage tach on the column and we powered it by splicing into the wire going to the dash tach. I believe it to be accurate so it would seem that the signal is good. Not?

[mjb765]

Here's a shot in the dark. MSD makes a tach adaptor. Basically it's a signal amplifier. Maybe Pertronix makes one too.  Maybe there is a signal issue here rather that a calibration issue. You might be battling a weak or floating input signal. Other than using an oscilloscope to check amplitudes I dont know any other way to accuratly check the input signal to the tach. Also you can see if it's a clean signal or not ie. amplitude  differentiating or attenuating signal patterns. If the signal is dirty you can back track it with in the circuit to the source. This was one of our trouble shooting techiques we  did in my main frame gate chasing days.

I have an Autogage tach on the column and we powered it by splicing into the wire going to the dash tach. I believe it to be accurate so it would seem that the signal is good. Not?

makes sense to me....

[Chryco Psycho]

you usd to be able to just buy the kit for $70 or so & do it yourself from RTE

[Wedg2Go]

you usd to be able to just buy the kit for $70 or so & do it yourself from RTE

I know this is an "Old Post", but thank you Chryco Psycho for that bit of info. Much appreciated!

[Chryco Psycho]

Glad to help , I have upgraded a number of tachs using the RTE kit