Decided to convert my 70 tachometer from cable to electric. One motivator is that cable drive stuff is pretty obsolete today. Had to buy a special order HEI with cable drive for the 68.

I bought an electric drive conversion kit from ZIP and it looks like I'll have to return it. The unit itself looks well made. The instructions that come with it are pretty terrible. There's a discussion in the instructions on how to calibrate it with a signal generator! Surprising that this kit is be marketed assuming customers have a signal generator. There are three wires coming from the unit......no mention as to which wire is what. Also annoying is that no connectors are included for the wires......particularly the wire that will presumably go to the HEI distributor. If I use this kit, I have to look for an HEI connector. Another thing is there is no instructions for removing the needle off of the donor tach. Actually, I know how to do this, but a lot of potential customers would be clueless. It's easy to bugger the thin shaft going to the needle. To remove the needle, use a kitchen fork. Insert the fork under the needle with the shaft between two of the tines and pull up.

Has anyone made this conversion and can recommend a service provider?
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Background: The bracket, that attaches the steering column to the bottom of the windshield birdcage frame, interferes with a tach cable drive. Perhaps the reason is that this bracket is stamped steel from a 82 Corvette. Earlier C3's have a gross cast iron bracket and I decided to save a few pounds and buy an 82 bracket.

Also, I've discovered another repro wire harness manufacturer: American Autoworld. Add this to the list of Lectric Limited, M&H, and Painless.

My existing tach has a 6000 redline for the 454. Decided to keep this for my new engine.

 

perhaps big2bird will chime in. and he's not so distant from Torrance.

 

I do have a Sun tach generator, but I would use an interface between the HEI tach output and tach board. Ask Lionel, or Richard.

 

As for calibration, notwithstanding the installation instructions, the ZIP service rep said I didn't need to calibrate the unit. Apparently it's good to go.

Modificaion of the original tach housing took a long time. There are two tiny bolts to mate the electric unit to the tachometer canister housing. What serves as nuts for these bolts are brass inserts in the unit's circuit board. The main part of the unit is a GM part that has been modified to bolt into tthe C3 tach housing. To the extent that the kit exists of the GM part, it appears to be of great quality. I suspect that the circuit board with the inserts is not part of the original GM part. Unfortunately, when I went to snug up the attaching bolts, the inserts in the circuit board started spinning........I could not tighten the little bolts, nor could I loosen them. After about an hour, was able to retract the attaching bolts, make some modifications, installed the attaching bolts and got the electronic tachometer unit installed in the tach cannister.

Next surprise. When you go to attach the needle, you need to have 12 v DC applied to the electric tach. red wire +12, black wire ground. 12 volts with no tach signal places the tachometer shaft at 0 rpm. When you apply 12 vDC, 0 the tach needle, and then disconnect the voltage supply, the needle will wander! With no voltage, it points straight down and doesn't point at zero rpm. With no voltage, holding the tach horizontal, you can manually place the needle anywhere, and when you apply voltage, it returns to 0. So a disadvamtage of this unit is that with the ignition off, the needle doesn't read 0 rpm, but rather points straight down. I think this feature would give a NCRS guy major problem.......actually, I don't like it but I can live with it as long as the tach works when the ignition is on.

If you install this kit you'll need a connector for an HEI distributor (if that's what you are using). The kit red and green wire are the standard color configurations for the HEI distributor.