Tach Installation

[flyingdiver41]

I have a 78 CJ7 with the AMC 232 i6 engine using an HEI ignition system. My question is, I'm wanting to install a tach but am unsure of a couple things.
#1 Because I have an HEI ignition system, will that influence the type of tach I purchase?

#2 Does the tach have a mechanical connection or does everything run through the distributor?

One more question I have is, what maintenance manual do you recommend? I 've seen on other posts that its NOT chiltons.

Thanks for the advise.

 

[flyingdiver41]

30 reviews and no one knows anything about Tach's huh??

That surprises me about this group.

 

[IOPort51]

I do know that tachs are not a cut and dry subject and I would have to say check the manufacturers cut sheet. I know it was a challenge to put a tach on an MSD6 CDI system. I don't think anybody is ignoring you , it is just that that is a very good question with a lot of possible answers and only one of them right.

The best you can do is a factory service manual. A reprint will do but the diagrams are twice the size and there is one heck of a lot more information offered. Will run about $75 but worth every cent. Haynes and Chiltons give you just enough information to get into trouble.

 

[flyingdiver41]

Thank you. That's good info on the manual.

 

[Hedgehog]

There doesn't seem to be anything special about installing a tach. I'm assuming that your HEI has two connection plug ins. One is for a nice solid 12+ volts the other is for a tach. As far as a mechanical connection is concerned, well, I'm sure the supplied plug in has a mechanical component to it somewhere. Essentially a tach takes a pulse of electricity from one plug every other revolution. I installed a NOS Autometer Tach. This tach allowed for operation on a 4, 6 and 8 cylinder engines. How? There were several small wires exposed, don't cut any and you were set for an 8 cylinder, for a 6 you cut one of the wires, for a 4 you cut another wire. Simple easy instructions. So since I have an 8 I plugged her into the HEI dist., supplied swithed power for over all power and supplied power from the dash light circuit for the light and the darned thing works. I bet most other tachs are the same or similar. Newer ones probably have DIP switches rather than cutting wires, but are close enough.

As far as manuals are concerned. I hate my Chiltons manual. I have one and it has been handy so they aren't worthless, especially for the clear writing in the wiring diagram. Too many times when doing something complicated it says something like, "to rebuild the carborator, first remove the carborator." WHAT! Exactly how do you correctly do that?" The Haynes manual is better, but you simply can't beat the dealer shop manual. Sometimes you can cheat a little. The 1981 manual will have much the same information as the 1984.

 

[IOPort51]

Jeep 1979 CJ 5 CJ 7 Color Wiring Diagram 11 x 17 | eBay

this is also a terrific investment for less than $20. If you look he more than likely has a 78 I just keep this one bookmarked.