tachometer in Gremlin V8

Hello,
i've problems getting my tachometer running in my Gremlin V8.

I've change the ignition to HEI ( http://www.aipelectronics.com/index.php/catalogsearch/result/?q=DJ8-DF&x=0&y=0 - http://www.aipelectronics.com/index.php/catalogsearch/result/?q=DJ8-DF&x=0&y=0).

The tach i've bought is a NOS with part#3678160 and as it's a 6cyl one,  i also bought an adapter (SGI8 form dakotadigital) for converting to 8cyl.

Think, i've connected everything correctly, but needle of tach is moving only a few millimeters (4cyl only minimal, 10cyl about 5-7mm).

I've found out, that there a two different type of tachs around: current and voltage triggered.
As mine has only connectors for 2 cables i think it should be a current triggered on, correct?

...in combination to a current trigger tach i've also read, that there should/will be also a "ballast resistor" in the circuit - actually i've none, can this be the problem?...and if yes, how "large" should it be?

would be great if someone can give me some hints
thanks in advance and best regards

toolmanxiii wrote: AMC tach's run in series between the Ignition on and the coil and use the pulse to activate . HEI Dist's don't pulse enough to give a good signal. I've taken aftermarket tach's , removed the cover and mounted them in place of the factory ones . this way they use the signal from the Tach clip on the dizzy .

Actually a correction to this. AMC used a current measuring meter that measured total current through the ignition and calibrated that to be rpm rather than a current reading. It did not work with a pulse. And it did work in series with the ignition.

And while I used to be able to pull from memories some of the early get arounds that could be used to make one work, it also depended on what igniton option as used on the car.
Lacking that memory, pretty much today, if you are not using an OEM ignition, the tachometer is not going to work.
All AMC Tachometers up until the middle 70's were current measuring tachometers.
The Javelins, if memory serves me correctly, the 8 cylinder tachometer was a pulse triggered tachometer while the 6 cylinder unit remained as a current measuring device.
As to other cars such as the Spirit's.
I think all of the tachometers were current measuring devices and you did not need an adapter to go from 6 to 8 and back again. They were calibrated for 4, 6 or 8 cylinder use by turning a potentiometer on the back of the tachometer and then stamped by the factory as to the application.
The bottom line?
as far as I know you cannot use a Spirit tachometer on anything other than the OEM ignition.
It seems to me a pertronix conversion had one variation that allowed that to happen, but working from memory as I write, I do not remember the particulars.
That may depend on the year and the particular model involved, but as I have had no desire to install a pertronix conversion, once I realized some of the features of the car would be disabled, I lost even that much interest in them.
If I am wrong on any of this than I stand corrected when it happens.
I know this information is covered in the TSM of your car. I have a TSM for every AMC car I have owned, or at least one that covered the important functions. The information as to what and how it worked would be there.

I had an issue keeping the factory tach after going to an MSD system. They have an adapter that allows it to work. Maybe it would work for your HEI. It was number 8212 I think. Give their tech support a call they were helpful for me.