75 Corvette tack

[Jim T.]

Anyone converted a mechanical 68-74 tack to the electronic tack like which is in the 75 Corvette?
The electronic board and a filter are available from Corvette parts suppliers.
Would only these parts be enough to change a mechanical tack to a functioning electronic tack?

[Lynn H.]

Re: 75 Corvette tack

Wouldn't you also have to change the Tachometer itself???
Lynn

[Joe L.]

Re: 75 Corvette tack

Anyone converted a mechanical 68-74 tack to the electronic tack like which is in the 75 Corvette?
The electronic board and a filter are available from Corvette parts suppliers.
Would only these parts be enough to change a mechanical tack to a functioning electronic tack?

Jim-----


I've never done it, but I don't think it would be any more difficult than changing the instrument and installing the circuit board and filter. In other words, just changing the whole thing to the 1975+ configuration. The 75-76 instrument should install in the dash with little, if any, problem.

By the way, if one is so-inclined, one can also convert a 68-72 mechanical oil pressure gauge to the 73+ electronic gauge simply by installing an appropriate oil pressure sender, connecting wire, and 73-76 gauge.

[William C.]

Re: 75 Corvette tack

I'd be a little more careful with the tach setup as the pulse put out by the magnetic sensor in the HEI system used in '75 is much different than the signal given off by the points in a distributor. I'm not an EE, but I'd be very cautious about how the signal was obtained so as not to blow out your new circuit board.

[Joe L.]

Re: 75 Corvette tack

I'd be a little more careful with the tach setup as the pulse put out by the magnetic sensor in the HEI system used in '75 is much different than the signal given off by the points in a distributor. I'm not an EE, but I'd be very cautious about how the signal was obtained so as not to blow out your new circuit board.

Bill------


Yes, that's a very good point. I had not considered that.

[Michael W.]

Re: 75 Corvette tack

By the way, if one is so-inclined, one can also convert a 68-72 mechanical oil pressure gauge to the 73+ electronic gauge simply by installing an appropriate oil pressure sender, connecting wire, and 73-76 gauge.

Joe,

73's still had a mechanical oil pressure gauge. I think '74 was the first year for electronic.

[Jim T.]

Re: 75 Corvette tack

I'd be a little more careful with the tach setup as the pulse put out by the magnetic sensor in the HEI system used in '75 is much different than the signal given off by the points in a distributor. I'm not an EE, but I'd be very cautious about how the signal was obtained so as not to blow out your new circuit board.

William reference my prvious post, I installed a ZZ1 350 crate engine in my original owner 70 in 1991 and the engine came with a HEI and have had no problems with it. I am wanting to see the tack needle operate and just considering my options. A used 75 tach, installing my 70's original tack drive distributor in the ZZ1, or modifing my original tack to function as a electronic unit.

[Paul D.]

Re: 75 Corvette tack

Jim,
If your existing tach and cable are in good working order, my choice would be to replace the distributor. Don't feel obligated to use the original points type distributor unless you want to. Lots of options exist including breakerless conversions for the original distributor and complete new units from MSD,etc. I would rather change out a distributor than a tach plus additional wiring that will be harder to change back later if you decide to restore the car. Chip.

[Joe L.]

Re: 75 Corvette tack

William reference my prvious post, I installed a ZZ1 350 crate engine in my original owner 70 in 1991 and the engine came with a HEI and have had no problems with it. I am wanting to see the tack needle operate and just considering my options. A used 75 tach, installing my 70's original tack drive distributor in the ZZ1, or modifing my original tack to function as a electronic unit.

Jim------


There's another option. You can purchase a GM HEI distributor which has been converted to tach drive. These are not cheap at about 500+ bucks, but it is an option for you.