Update:
I was installing a Wideband data logger and had to tap into my black/violet wire for tach signal. I removed the female connector at the tach and tinned the two wires together then installed a new female connector. No tach signal! So I went into the trunk and opened the connector pictured in post 33. I used a continuity tester with one lead at the tach connection and one at the black/violet in the 3 pin connector. I got continuity with the test lead pressed all the way into the female 3 pin but no continuity on the female pin itself unless I wiggled the test lead. I removed the black/violet pin in the 3 wire connector and found a bad connection so I tinned the wire and installed a new female pin connector. All is well and I now get continuity at the pin without wiggling it.

Good, now that its past 12, got to post # 35

Hi all, I kinda highjacked this thread last year, don't know if the OP ever got his tacho working. I still have a non-working Tach and itching to get it going.

I'm running a Permatune 3-pin without any MSD tach adapter. Not sure whether this was stock on a '76911S 2.7L, but it worked fine before I did my engine drop.

I did a continuity check on the black/purple wire off the back of the Tach back to the spade connector on the side of the distributor which I believe is where the Tach should get it's signal. Continuity check was Positive (i.e. good connection).

I'm thinking either a) I am not getting a signal to the Tach; or b) Tach is fried.

How do I check whether the distributor is giving a good signal to the Tach?

Update
I broke down and bought a nice tach-dwell meter. I'm getting a good signal at the tach. So my problem is the tach. I can certainly remove and send to our host or one of the other reputable gauge experts for repair, but before I do so should I open it up and se if it's a simple repair like replacing a burnt resistor?