Got a 89 F350 w/351W. Prior owner gutted all factory bs and installed a carb and a 6AL MSD ignition a MSD dist. and coil. Looking at the MSD web site it looks like I can connect the tach wire right to the 6al box. Has anyone done this? And what color wire is the tach wire? All sensors are gutted also. the wire harness is a little hacked up, all wires are visable. Got the Haynes book but a little confusing. Thanks alot I'll try to get some pics up soon.

 

Just tap into the neg wire of the coil, that will give your signal. Dont know if there is a specific wire on the box but my msd 6a is on the neg of the coil, for the tach.

 

DO NOT tap into the negative wire of the coil! MSD is multible spark discharge, the coil gets as many as 3 strikes per ignition cycle and the msd boosts the voltage to the coil. This will really mess up your tach.

This is why there is a tach out put on the box. It's a single spade plug on the oposite end of the box from the wiring next to the rpm limiter pill. Attach all tack signals there it provides a clean safe tack signal.

With most stock distributors and "some" MSD dist. you can use the signal wire that goes from the dist to the spark box it's usually green (green has become the standard tach signal color among aftermarket ign companies) I can't remimber what color it is on a stock dist. But I'm sure somone can chim in and tell us. However many high end MSD dist and probably yours don't provide a tack signal from the distributor that is apropriate for a tack, or even running a coil without the spark box.

 

I found the spade connector on the side of the 6AL box. I wasn't sure because it's a multi spark if i need an adapter for the tach to reg. the signal. So tach right it to the side, Does anyone know the color of the tach wire?

 

If this is true that the tack it attached at the coil and your tach is working then your 6A box isn't.

 

With every aftermarket tach I've ever seen (and that's alot) it's green. I don't know the factory wire.

 

Thanks Opossum, factory tach. still trying to clean up the hack job and get all instruments gauges working. One at a time, thought that would be the easy.

 

It apears in the wiring diagram I found that the factory signal wire from the tach is dark green with a yellow stripe. You should be able to find this wire in the harness from the firewall that originaly went to the coil and distributor. It's probably bundled with the red with lt green stripe wire that powerd the coil and if it helps is pin #4 on the ECM plug.