[i82much]

I have an MSD ready to run distributor, and I just had a shop install rally gauges in my car. The tach works fine. The rev limiter on the MSD distributor is set by grounding the tach wire. So, I went in and ran a jumper to the back of the tach (under the assumption that is where the MSD tach output is hooked to). When I picked up the jumper, I got the crap shocked out of me!

I really don't get it. Is that possible somehow if the tach was wired to the coil instead of the distributor tach output? Shouldn't the coil just have 12 volts?