This is the first time that I have posted a question. I have a 71 Nova SS with a 396 4 speed. Here goes my question. My nova originally had an hei distributor in it. I had problems getting the dash cluster tach working. I was told to put a tach adaptor in, and that didn’t work. I found that I needed to jump the tach wire to get it working. I left the tach adaptor hooked up, because things were working. I was having problems with the distributor, so I went to a regular distributor with an external msd blaster coil. It made a big difference to how the car runs now. My problem is that I took the tach wire that was hooked into tach on the hei, and hooked it to the negative of the coil. The tach now bounces up and down. It’s fine when I am idling, and it works as I am stepping on the gas, but it gets to a point where it just bounces up and down. Like it is losing the current. Any suggestions.