I have a carbed 350 on a 1990 Camaro RS. Put in a crate 350 HO Deluxe about 4 years ago. Last week I replaced the MSD-6A ignition with an MSD-6AL, which is the same damn thing only with a rev limiter. Anyway, after the swap, the tach wasn't working - it was fully pegged. So I took the cluster apart and checked the resistors I wired in there (standard tach fix) and all was fine. When I put it back together and turned the car on, the tach initially moves a little bit when the key is turned to the on position, but after I start it, it just sits there and doesn't move at all no matter that RPM the car is actually running at.

Anyone have a clue what I could have possibly done wrong? Is it possible the tach output on the 6AL is faulty?

Only thing I did differently otherwise was mount the box on the firewall.

 

Have you tried swapping the 6A back in?

 

Not yet.