Tach wiring question, MSD ready to run, auto meter, and oem tach

[4mulas]

Hi there, have a MSD ready to run with four wires. Black, red, orange, and Gray for the tach.

Question is:

Can the Gray wire be used to supply to the necessary signal to both the Auto Meter tach and the oem style in-dash tach (1969 roadrunner), or do I need to take the signal for the oem in-dash dash tach from negative side of he coil? Seems like a silly question I know, but I think each system runs on a different voltage and a, not sure if there’s any special requirements for this.

If the gray wire can be used to supply both my intention is to run just one wire from the interior of the car to the msd distributor and just splice it inside the car.

The ballast is bypassed for the msd.

Thanks in advance for your help. PS. Making the wiring harness in the next hour or two so speedy answers are appreciated!

 

[dvw]

The MSD requires a tach adapter between the grey wire for the factory tachy on the tach outlet at the MSD.
Holley › ... › Tach Adapters
Web results
MSD 8920 Tach/Fuel Adapter - Holley
Doug

 

[4mulas]

The MSD requires a tach adapter between the grey wire for the factory tachy on the tach outlet at the MSD.
Holley › ... › Tach Adapters
Web results
MSD 8920 Tach/Fuel Adapter - Holley
Doug

Thanks, but that adapter is if you’re running a MSD Box with the green/violet wires for magnetic pick up etc....

I’m running the MSD Ready to Run distributor, no separate msd ignition. The gray wire off the distributor is for tach feed with no adapter required... was just wondering essentially, if it can be split to feed two different tach’s. One oem. And one auto meter aftermarket.

 

[BLK 68 R/T]

I have the msd 6al tach wire going to the 8920 tach adapter, the tach output wire from there is split to the tach and the computer module input for the efi. Works fine for me.

 

[BlackDogHemi]

I have the RTR and the tic-toc-tac won't work, although the clock does. Hoping the tach adapter will solve it. Good luck.

 

[Wietse]

I also use a RTR MSD distributor (8387) and a Blaster SS coil, and can confirm that the OEM tach will not work.
I had to use the 8920 tach adapter to get the tach to work.
https://www.holley.com/products/accessories/gauges_and_gauge_accessories/tach_adapters/parts/8920

I believe i hooked up the gray wire from the distributor to the tach adapter input and from there on to the oem tach.

 

[BlackDogHemi]

That's good to know that with the adapter the tic-toc-tac will work. I just mounted a Sun Tach in the tach window.

 

[Billccm]

I like the rt-eng.com tach solution. It accepts MSD and other electronic ignition tach signals without a adapter. Accuracy is good if you get the built in calibrator version. Some videos below:

http://www.average-guys-car-restora...ing-tach-for-68-road-runner-project-beepbeep/

http://www.average-guys-car-restora...-for-68-road-runner-project-beepbeep-part-ii/

http://www.average-guys-car-restora...for-68-road-runner-project-beepbeep-part-iii/

http://www.average-guys-car-restora...-for-68-road-runner-project-beepbeep-part-iv/