Stock tach on 70 Cuda, how to make work with MSD?

[TonyBolton]

Trying to get the stock tach to function. How do I do this? Can I plug into the port on the MSD box?

Thanks!

[hotrdblder]

go to negative side of the coil

[TonyBolton]

Thank you for the help, thats what my Dad was thinking but just wanted to make sure(my luck i'd fry something).

Can you tell me what color wires are what? I hate to lead you down a blind road with this diagnosis, but any help is appreciated.

I've got a lime green wire that I "think" is the one I need, but i'm really outta my league on this part.

[hotrdblder]

not sure most tachs are 3 wire, one for tach,one for ground,one for light.
pics?

[TonyBolton]

Well, i've been searching and scouring the net for something, and the best i've been able to come up with is the below image.

If I need to, I'll snap some pictures but my Dad has the car at his house and i'm at mine.

Again, I appreciate your help!

https://www.pro-touring.com/forum/attachment.php?attachmentid=19350&d=1191098063

[hotrdblder]

i guess, but uaully they have another wire for a dimmer light for at night, but you shouldn't hurt anything so do it up, goodluck

[TonyBolton]

Ok! Will do! Bein' the son, I don't wanna start trying wires with my Dad there, something go wrong, then I hafta hear the I TOLD YOU SO speach. ;)

Thanks for your advice, i'm gonna try it tomorrow.

[MrQuick]

There should be a tach lead coming off of the harness...I believe it is a brown wire with a black connector.

[TonyBolton]

Well, we tried the wire we THOUGHT was the one, but it didn't work. When I have some more time, i'll get under there and start hunting around.

THanks for the info guys, I printed this thread off for future reference.

[MonzaRacer]

which unit do you have? If its a CD (ie other than an MSD 5 ) ignition do not go to the coil negative.
On my GM Heavy Duty ignition which is a MSD6T it says to use the white wire to feed a tach but some units need a signal filter as the tach is seeing a opening and closing signal nad the MSD doesnt produce that signal.
MSD has a forum you can ask specific questions and they can verifiy and give you p[art numbers.
Lee