About Us

.: corvette tachometer


    In the 1970's the Corvette started using an electronic tachometer. I wanted to keep the original tach., so I had to figure out what signal it was receiving from the distributor.  

   This is the back of the tach. - only three connectors: power (p for pink), ground (bk for black), and brown from the distributor.
    I couldn't find the specifications for the signal going into the tach., so I guessed it was a pulse of some shape?

    This is a old Heathkit power supply I bought in the early '70's that I use for supplying simple signals. It has a square pulse output, but only goes down to 200Hz.
    Doing some quick math, 200Hz is equivalent to 12,000 rpm! But, an 8-cylinder engine has 4 ignition pulses per revolution. So, 12,000 rpm divided by 4 = 3000 rpm.

    If my guessing is correct, if I put a 200Hz square pulse at the tach input, I should get 3000 RPM on the tachometer. To be safe I set the voltage low (3 volts).

   And,... it worked.

   Okay, not an exciting ending (and no picture), but it's better than smoke and fire.


    There is more to come as I need to make a triggering device that mimics an 8-cylinder engine - 4 pulses per revolution.
    I already have the parts, and have tested it, I just need to build it and mount it to the motor.