Okay i hooked up a msd 6a ignition box the other day car ran fine,sounded alright but i just noticed my tach isn't working now...what did i do wrong and how do i fix it

Strait from MSD's site:

<b>"Tachometer Operation
If your tachometer doesn't read correctly after installing an MSD, you may need a Tach Adapter. On GM vehicles, first remove the tach filter. There are two MSD Tach Adapters. Contact MSD Tech with the manufacturer of your tach and what you have installed on it to determine which Tach Adapter you will need."</b>

Happens now and again.

i read that to but don't know what they are calling the tach filter, guess i'll have to call them

Some cars have 'tach filters', you can trace this down in your harness which will be one of the white wires that went to the coil originally and remove it. This will be with in 1-1 1/2 feet of the coil, unplug the filter reconnect the wire. It should be a small cube shaped black piece that has a white wire going in and white coming out. HTH.

Nevermind.............i was messing around today and saw the tach wire's pigtail slid out since the clip is broken, plugged it back in and tacho.