How can I know if my factory tach is accurate? How accurate are they usually?
Also, can the electronics be upgraded to work in conjunction with my MSD 6AL ignition? I have been using an Auto meter for the past 10 years, and I want to get back to a stock look, but make sure the factory tach is accurate.

MSD makes a electronic unit that is a go between the stock wire and the MSD 6L plug. It works fine on my same set up in my 71 B. The unit is small, a coup

To Connect your stock OEM Mopar tach to your MSD ignition box, MSD has a tach adapter that plugs into the Ignition box. (Part no 8910 or 8920) It converts the MSD signal for your stock OEM mopar tach.

A second option, there was a posting from a Moparts member, Mr Heaterbox, who was making new replacement circuit boards for OEM mopar tachs to work with MSD style ignitions. Search on this posting number: 5790084. Seems interesting but not sure how well it works.

sorry---couple inches square and easy to hide.

I'm not sure how accurate it is, it seems OK and maybe I should hook up a "real" tach to see. Keep in mind the original stock ones were probably off as well.

Pic for scale....

And if the unit is going to be out where you can see it mopar performance has MSD's tach adapter unit rebadged for their offering...My rallye dash tach is accurate but the weight of the moving parts gives it a slow sweep....My 500hp 440-6 will rev up much faster{in neutral} than the tach can sweep when bliping the throttle...Definitely not the instant response of a new performance tach

I tried the MSD tach adapter and my factory tach works....some of the time. It reads way higher other times. The cluster is well grounded.
I have since had Redline gauges rebuild my cluster including replacing the tach internals with modern VDO internals. There is no need to use the tach adapter with this setup, which is vastly more accurate. Let me know if you want my slightly used adapter.

Seems like ALL original tachs read way high. While I can't prove it, it seems like this might have been intentional to try to keep people from blowing stuff up under the factory warranty. Just seems very odd that they never seem to read too low, always too high.

MB

The MSD tach adapter works, but it makes a rapid tic-tic-tic sound while operating. I hid mine up under the dash, but I can still hear it if I don't have the radio on and the windows are rolled up. Kind of anoying.

I'd suggest trying one of the other methods.

Tav

Change it over with a NEW kit. Do u clock while ur @ it.I did mine.

DASH WORX FROM RTE

Ditto on factory tach being off. Also, I tried a tach adapter and that too was unreliable.

I have had three rallye tachs upgraded to accomodate for a multple spark ignition system.
If you go this route, depending on who you use, you likely need to specify that you will be using a MSD type ignition. Otherwise, they may rebuild/recalibrate for a factory system.

I tried the tach adapter however, my tach was off so I didn't trust the information that