Author Topic: Pertronix wiring for 67-8 factory tach cars. ( Instructions)  (Read 466 times)

The Going Thing

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The job isn't that difficult if you do basic mechanical work. You'll need about 6' of 14 gauge black wire and a Scotchlok.( used black wire instead of red because it's easier to camouflage when you run it with the three wire engine feed under the three clips that should be on the valve cover bolts on the engine.
 
You'll need to remove the instrument cluster from the dash. ( I can give you the simple way to remove it if you haven't removed it before)
You'll need to make a very tight loop on a metal hanger. Strip about 3" of the end of the wire, pull the stripped end through the loop and twist it on the exposed wire tightly. You'll  then lubricate the hanger with a little bit of dish soap. Insert from the firewall side the hanger into the boot next to the wires that exit from the engine harness and push the metal hanger into the car. ( You are NOT poking a hole into the boot, starting the straightened hanger into the car
and slowly pull the hanger and the wire into the vehicle.  Cut the wire from the hanger and pull it in to the right side of the  dash opening and you'll use the scotch lock to the red tach lead of the main dash loom.  The other end of the lead is attached to the RED lead of the Pertronix.  You have a couple choices here.  You can either solder them together and use a little shrink tube, or you can use a bullet connector. 
The black lead from the Pertronix remains on the black terminal of the coil.

Anyway, the cluster removal is relatively simple.. After you've done it a couple times.
There is a stamped nut that holds the radio to the support bracket under the dash. You can access it without removal of your of your gauge cluster under the dash.  You'll remove the single stamped nut with a 1/4" drive 7/16" socket. There are four screws that hold the radio bezel to the dash. Two black in the black part of the chrome bezel and two stainless screws.  The radio will pull forward. On the left SIDE of the radio there are two plugs. One is for the radio lighting and power, the other to dash speaker. ( I'm assuming you have the stock AM or AM/FM radio.) The radio antenna lead is on the right lower side to the rear of the radio. Unplug them and set the radio on the passenger side foot well out of your way.
On the right lower corner of the instrument cluster there is a 3/8" sheet metal nut. Remove that. Use a 1/4" drive socket to remove the nut. Set it with the screws and nut you'd removed previously.  Now you'll remove the screws in the bezel. There are three black phils above at the top of the cluster, and two below. One under the tach and speedometer.  Remove those. All the way left there is one stainless screw above the temperature controls. Remove it.
Now loosen the two screws on the top of the temperature control. No need to completely remove them.
Now remove the steering wheel and set it aside.  Double up  a towel and lay it over the steering column.
Grab the cluster and wiggle it back and forth until you can get your finger tips under it. Continue to wiggle it until you  have enough room to unscrew the speedometer cable from the back of the speedometer.  Once you've done that you can lean tilt the cluster forward at the top. Unplug the black connector from the windshield wiper switch.  The left side turn signal lamp needs to be unplugged. ( Single bullet lead) Now unplug the white block connector for the cluster to harness. ( Pinch in on the sides and pull and wiggle.)  Now set the cluster loosely back in place. Lean over in the seat to the right and pull the cluster forward from the side. Unplug the tachometer. One red one black bullet lead.
You can now remove the cluster. Be careful. Walk it side to side and it will slide forward. BE SURE THE COLUMN IS COVERED WITH THE TOWEL!
You don't want to scratch the chrome on the cluster or the paint on the top of the steering column. 
Now you can get to the tach lead on the right with the wire and Scotchlok. 
Before you put the dash back together, be sure to test your work. plug the two tach leads in the harness together. It completes the circuit and the car will start. That assures the Scotchlok is correctly installed.
Assemble in reverse order. 
If there is further clarification needed, let me know.
Your tach is now safe and will read correctly.
« Last Edit: May 27, 2020, 12:59:57 AM by The Going Thing »

S7MS427

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #1 on: May 27, 2020, 12:24:57 PM »
Going Thing,

Thanks for posting.  I currently have the dash out of my '67 so I just may do this job this weekend.
Roy Simkins
http://www.S-TechEnt.com/Shelby.htm
1966 G.T.350H SFM6S817
1967 G.T.500 67400F7A03040

JD

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #2 on: May 27, 2020, 02:07:11 PM »
This might help, I can remove/delete if not wanted...

(this is a later unit note bulb sockets are plastic)

'67 Shelby Headlight Bucket Grommets http://www.saacforum.com/index.php?topic=254.0
'67 Shelby Lower Grille Edge Protective Strip http://www.saacforum.com/index.php?topic=1237.0

2112

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #3 on: May 27, 2020, 02:16:49 PM »
Pictures always very helpful.

Shelby_r_b

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #4 on: May 27, 2020, 02:30:23 PM »
Pictures always very helpful.

+1 - Thanks, JD!
Nothing beats a classic!

The Going Thing

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #5 on: May 27, 2020, 08:24:22 PM »
JD-  On the right side as it posted you might want to circle that single bullet connector which is for the LH turn signal indicator.  It is a stand alone item so to speak. I would have taken pictures had I knew so many have had issues.  I have been supplying this in messages for many here and on two other forums. 
It works great and the tach reads correctly.
You're all welcome for the post. I was trying to take the mystery out of doing this job.

rmarble57

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #6 on: May 27, 2020, 09:30:33 PM »
This item has been previously discussed and an alternate way to skin the cat is as follows. 

If you have an ignition system that requires a full 12v to power either the electronic "pickup" or an electronic distributor, you have a few choices, but here is my favorite.  For clarity, the tachometers in the 67's work when they receive a significant drop in voltage as a "counter".  The normal voltage going to the coil is somewhere around 9v as the power wire going from the ignition switch through the engine wiring harness wires contains resistance wire that drops the voltage.  When you put the full 12v to the coil "+", the drop in voltage on each firing cycle isn't enough for the factory tach to read.  I've seen many attempts to circumvent this situation including external tach control boxes etc, but I've been running it this way for quite a while and no issues.

Rather that trying to tap into the tach wire for the drop in voltage from the coil that makes it work, you can also do the following:

Leave the resistance wire from the key switch to the coil intact and just provide a full 12v to the pertronix or other electronic distributor from the key switch.  You can use the "scotch-lok" or as I prefer, a "posi-tap" to take the full 12v from the same "keyed" ignition switch wire before it gets to the resistor wire and just run that same black wire from there to the power input to the distributor.  Just take the ignition switch bezel off and drop the switch and wiring down and you can get to the wire needed.

I ran the wire out through the same grommet as described above and tucked it in with the engine wiring harness and it is very hard to see.  The "+" side of the coil is just a convenient place to get power for any electronic distributor system.  The "-" side is what gives the jolt to the plugs. 


Hope this helps.  Just offering an alternative.

JD

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #7 on: May 27, 2020, 11:07:22 PM »
Added "left-turn" call-out...
« Last Edit: May 27, 2020, 11:09:35 PM by JD »
'67 Shelby Headlight Bucket Grommets http://www.saacforum.com/index.php?topic=254.0
'67 Shelby Lower Grille Edge Protective Strip http://www.saacforum.com/index.php?topic=1237.0

The Going Thing

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Re: Pertronix wiring for 67-8 factory tach cars. ( Instructions)
« Reply #8 on: May 28, 2020, 12:04:59 AM »
Thank you, JD. Hopefully this will be helpful to others who find that the Pertronix II and III cause inaccurate tach readings and need instructions on fixing the issue and being able to hide it from most.
The cars start and run so much better with the Pertronix II units.