Whats involved with converting an early C3 (1970) tach to electric. I am assuming I can pick up a 75-77 tach and put my tach face on it.

Has anyone actually done this?

 

I just bought a used 73 tach off of ebay. I am going to use it to try and retrofit it with an autometer electric tach as the workings behind the face. It that works, I will swap it out.

 

Yes, the early face can be transplanted onto a elec tach, but the 2 small holes that secure the face use slightly diff spacing, so you will have to drill 2 new holes and hide the old ones.

 

I used the 75+ tach stock, didn't bother swapping plates, as it was so close anyway, not worth bother....

 

Gene, was it just a straight swap?

 

That'll work..Swap the face tho..Member 'MikeMercury' does this..

 

AFAIK ... '71 & earlier have greenish cast to numbers & tickmarks ... '72 up are white (like '75-'77 elec).

 

QUOTE=jackson]AFAIK ... '71 & earlier have greenish cast to numbers & tickmarks ... '72 up are white (like '75-'77 elec).[/QUOTE]


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The 75 to 77 have a different font style to the numbers too.. Swap the faceplate....

 

You will need an Hei distributor, Tach filter, and related wiring

 

Is the tach filter external to the tach? Is it different from the circuit board on the back?

 

I have a 74 and put 75 tach in it,but didn't swap the face because there was not much difference.A good vette guy will know the difference when you open the hood anyway.The tach filter is seperate from the board,but i was told by a very good corvette guy not to bother with the filter and i didn't put one and it works fine.After the hei is installed,3 wires one to the dist.,one to ground,one to ign.power.

 

I would hope so.

 

Thanks, sounds pretty straight-forward. What does the filter do?

 

Let me add this ... you may find it $ & time efficient to change to a NEW HEI dist that has a mechnical tach drive to run your OE mechanical tach. Star Performance has em brand new for about $163 ... complete from coil in cap thru tach gear to drive gear ... Star P/N 9200TDR ... Star ph 1-800-625-9454. Same piece that eckler gets about $400 for.

 

What? I don't even have a distributor. My PCM outputs an electric tach signal which is why I am switching to an electric tach.

 

OK ... you must have a late FI motor ... never mind.

 

I shouldn't be so hard on you. Your suggestion is quite valid for anyone else looking at this thread for ideas. Thanks for the tip.

 

i have not done this yet but i am going to. call clocks by Roger. www.corvetteclocks.com .

you send him your old mech tach and he fits it with a new elec tach, uses the same face and all. even repaints the face to freshen it up.

i am also sending him my spedo to rework. he will reset it to 000000 and repaint and touch it up also.

 

The fastest and easiest way to solve your problem is to put your hands on a working 75-77 tach and send it down to someone like Corvette Intruments in Fla. They will re-screen the faceplate to look just like your 70 green number tach. You can even specify the redline. IMHO it is not worth messing with trying to replace the faceplate with your old one and live with the hole mismatch for $50. Now, if the tach doesn't work, that's a little different. You will be getting into more bucks cause those replacement circuit cards aren't cheap (>$90). Total job to replace electronics and re-screen faceplate is north of $165. This of course doesn't include the cost of the original 75-77 tach.

The lowest cost approach would be to buy a defective 75-77 Tach (pay <$20), fix it by replacing the bad electronic parts and proceed as discribed above.

I had to do it both ways when I repaced the tachs on RamJet and the 69 FI vert.

Bullshark