Ijust bought a vintage tach from ebay, no name on front, has chrome bezel and a hammertone metal case, very neat and in mint condition. But how to wire it? There are six wires, black, red, yellow, blue, green and white. What goes where? I had a wiring diagram for an newer Autometer tach, but its gone missing, so I have no clue. Any and all advice appreciated!

Check this guy's webpage. He's got a lot of info on there about old tachs. You might even be able to identify yours.

http://www.musclecartachs.com/index.html

Thanks! Its an RAC GT model. Some wiring info is given, but I'll be having some wires left over. I'll post again after trying it.

I had an old Sun tach laying around. If I remember right you connected (or tied together) a different wire for 8 cyl's, another for 6, and the last for 4. This may explain the "extra" wires.

John, makes sense. I wired it as the webpage above described, and it works but the rpms are low compared to a known acurate dwell tach that I have. I'll try the other wire one at a time and then start mixing to see what happens. I know that some older tach have resistors to clip for 4-6-8 cyl, but nothing like that on this one. Anyone with any other ideas?