Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part JUNE's Ride of the Month Challenge!
  • May's Ride of the Month contest ended with a tie! Go to this thread to vote on the winner! VOTE HERE
1 - 12 of 12 Posts

·
Registered
Joined
·
1,181 Posts
Discussion Starter · #1 ·
I havr a msd 6a box, is the msd 8910 the correct adapter to use with the factory tachometer?

Thanks
 

·
Registered
Joined
·
10,553 Posts
I havr a msd 6a box, is the msd 8910 the correct adapter to use with the factory tachometer?

Thanks
I've never used the 8910. Both of my cars use their 8920. It will handle a "current" triggered tach (one that is wired through
the coil, like a factory Ford Mustang tach..... like the diagram below)
That same MSD part number will also work with a voltage triggered tach (one that has the tach trigger wire connected to the coil negative terminal,
like most aftermarket tachs)


758833
 

·
Dimples
Joined
·
5,963 Posts
I don’t know why, but my 6AL didn’t need an adapter. I wired it directly to the tach and it worked. Anybody have more experience with this?
 

·
Premium Member
Joined
·
14,213 Posts
I used the 8920 on several 289 HiPo cars; two ‘66 Shelby GT350’s and a ‘65 K code. The Shelbys had the original dash mounted tach and the K code had the Ford rally pac.
the MSD system used was the Digital 6+ box, MSD distributor, and MSD Blaster HVC-2 coil.

I was never able to get the factory tachs to work correctly without the 8920 adaptor

Z
 

·
Premium Member
Joined
·
7,590 Posts
Thanks guys.
One more baby step
What year mustang? There were current sensing and voltage sensing tachs depending on the year.
Another baby step question.....
 

·
Premium Member
Joined
·
7,590 Posts
Ok, that's a current sensing Tach. They didn't go to Voltage sensing until the early 70s, or so. Voltage sensing Tachs are what we all see today, in that, you can grab a signal off the "-" or trigger side of the coil.
 

·
Premium Member
Joined
·
14,213 Posts
More trivia, a la MSD and vintage Mustangs: if you want to leave the pink resistance wire (that goes from the ignition switch) in place, you can. Merely run the other end of it in the engine bay (that used to go to the coil) to the MSD box red wire. The MSD red wire is just a trigger wire, most ANY voltage going to it will turn on the box. It doesn’t have to be 12 v.
The box gets it power for all the ignition system needs directly from the battery.

I left the pink wire in place on all of my MSD cars thusly, because I could see into the future and knew sooner or later (uhh, ..... 15 years....) , I’d come to my senses and go back to a 100% stock (points) ignition system.

Z
 

·
Registered
Joined
·
10,553 Posts
So.... the red wire goes to the tach adapter and the black goes to 12v key'd?


Thanks
I don't have a factory setup but from the tach, whatever wire that went originally to the positive terminal of the coil, is wired to the red wire on the 8920.
And whatever wire coming from the tach that originally went to the ignition switch..... still goes to the ignition switch.
 

·
Premium Member
Joined
·
7,590 Posts
Based on my 65 Rally PaK (current sensing too), the black goes to IGN and the Red to the adapter. Where are your lighting leads? Maybe a blue and black?
 
1 - 12 of 12 Posts
Top