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?convert tach: mech to elec?

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
I'm thinking about converting my '71's tach from mechanical cable drive to a factory electronic gage from a '75-'77. In lieu of a deal on the pair, I think I can live with a green-number speedo & white-number tach. I've never looked at a 75-77 tach ... nor do I have a 75-77 wiring diagram ... but I understand they have replaceable circuit board. Is that board INSIDE the tach. If so, is there an additional EXTERNAL board? Other than patience, terminals & wire ... Am I gonna need any components in addition to the encased 75-77 tach? Thanks in advance!
JACK:gap
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
solo board's inside tach

I'm all for originality ... BUT my 71's already a fur piece away from original. Trying to break away from marriage to tachdrive distributors. There's many excellent non-tachdrive alternatives at lower cost. Got at least four tachdrive points distributors right now ... Can't justify the $ of unique MSD or Hyper HEI w/tachdrives & vacuum.

I did find tech article at Zip Products website that helps answer question about tach circuit board ... seems it's inside w/no secondary board.
JACK:gap
 
S

ssvett

Guest
Jack, If you want a "non point" system, why not go with the Pertronix(or similar brand) of conversion. The cost is usually under $100.00 and is very easy to install.....Steve
 
A

Alwyn678

Guest
Yes the Pertronix is the way to go

I Have the Pertronix II ignitor and the Flame thrower coil and it provides as much spark or more than the old msd distributor(nontachdrive) that I took off!!! E mail me and I will find the name of the company I bought it from...the ignitor II and the flame thrower coil delivered to my home next day was like 125 bucks..and it is Chrome
 
6

60w427

Guest
Jack - I had D & M Restoration rebuild my gauges last winter. They did an excellent job. I think they can convert your cable drive tach to electronic. Their number is 800-722-0854.
 

zwede

Well-known member
Joined
Feb 6, 2001
Messages
51
Location
Plano, TX
Corvette
1971 Coupe. 454 EFI, 5-Speed.
I did this conversion on my 71 a few years ago and it turned out great.

You can move your stock faceplate to the 75-77 tach and it will look all stock (and you'll get the correct redline).

Very easy to hook up.
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Thanks guys!!! I have an array of points distributors ... two with vac advance. I also have two MSD 6 boxes & a MSD canister Coil & Spiral core wires. This daily-driver 355 has a mild 224°@.050"---0.460" hydraulic cam w/ about 9.5:1 CR. What I may do is this: Install a non-TD points distributor w/vac advance along with MSD 6 & MSD coil & spiral core wires. Remove 71 mech tach & obtain & replace w/ 75-77 elec tach & swap-out faces. Also, obtain & install Pertronix Ignitor 2 as trigger for MSD.

I'm sure it's easy, but I would like to find how to hook up the elec tach (I don't have the tach yet & don't know how many connections there are)? I've confirmed the Pertronix is compatible w/ MSD 6. The MSD 6 does have a discrete tach output/trigger wire & MSD tech tells me no tach adapter should be required.
JACK:gap
 

zwede

Well-known member
Joined
Feb 6, 2001
Messages
51
Location
Plano, TX
Corvette
1971 Coupe. 454 EFI, 5-Speed.
Tach has 3 terminals: ground, +12V and tach signal. Haynes has the pinout of the connector in the electrical schematic. You can take the 12V from the feed of one of the other gauges.

Why not get a HEI? Large cap is much more resistant to cross firing. Much easier wiring.
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Zwede:
Thanks for connections tip. Large cap of HEI is something I'm considering ... especially w/MSD box's output. Also like the easy $ availability of whole HEI dist & parts.

Anybody got a water pump pulley spacer/shim kit for sale? Need the kind that goes between pump hub and pulley. Moroso #64035, Mr G #6129, Weiand #8230.
JACK:gap
 

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