How to wire a 60s 3 wire tach to an HEI distributor

Mello334

Newbie
I recently purchased the tachometer for my 67 riviera... The tach I purchased only has 3 wires red one for ignition (I'm assuming), black for ground and blue one for illum... All the newer tach I've seen has a green wire that goes to the HEI... Any help or feedback will be greatly appreciated... I also attached a couple pictures
 

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You can try hooking it into the yellow/brown wire, but I am not sure it is going to work. I only tried it once and was barely able to get the tach to react to the signal:(
 
You can try hooking it into the yellow/brown wire, but I am not sure it is going to work. I only tried it once and was barely able to get the tach to react to the signal:(

Which yellow/brown wire? It's an aftermarket hei distributor, if that helps... I'm lost right now... I don't want to install it wrong and fry my tach (from what I've read on other forums)
 
I may be wrong, but I don't think an HEI distributor is going to trigger a tach designed for a point system. You will have to find out the make of the distributor and where the tach should be connected. I believe it is the grounding wire from the coil. If that tach is important to you, you will probably have to convert back to a point system to use it. Personally, I run points in all the appropriate places, they are much better than the reputation people give them.
 
First, when you say HEI, do you mean the GM Big Cap HEI? Reason I ask is because guys commonly refer to anything that isn't points, ie, electronic ignition as HEI. If it is the GM big cap HEI, the cap has a tach terminal, and there is a really good chance that it will work just fine, maybe not be the most accurate, but it will work.

Aftermarket tachs commonly have a power, ground, signal and lighting connection. That isn't true of the OEM tachometers. They were commonly grounded to the dash, had one signal wire, and a plug in lighting connection.

If it was me, I would not worry one bit about burning anything out. If you are, just use a small inline fuse when you hook things up to any power. Looking at the back of the tach, that blue wire looks like the plug in light bulb. That, I would tee into the illumination circuit off the headlight switch. You could even tee it to something like an ash tray light or radio illumination circuit.

One of the other wires is a signal wire. What I would do is ground the case, then try hooking one of the other wires up to the tachometer terminal and look for function of the tachometer.

Here is the tachometer section of the 1966 Chassis manual, not much help, but it looks like that red wire to the center terminal is the signal wire.

 
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