In this thread "SOS" means "Same Old Sh!t". Last winter I refurbished my dash with all new Livorsi gauges. From the beginning the tach has worked fine until it gets to 3200 rpm and then it just craps-out. I've run grounds from the dist. cap and coil bracket to the block. I rerouted the coil and sparkplug wires as far from the tach neg. wire as possible. Also installed a filter supplied by Livorsi with no change. So now it’s time to start replacing stuff. The engine is a ’96 carb’d, gen6 502 and has a thunderbolt ignition.
Question: In what order do I start replacing parts to most likely fix the problem? (plug wires then coil, etc.?) or which parts in what order? My Dad taught me to replace the cheapest parts 1st, but that may not be the order to most likely fix the problem. Thanks for your help.

Have you sent the tach to Livorsi to have it checked???? or tried a different tach??? I would start there.
Just because it was new, does not mean that something is not wrong with it.

Actually not...I guess this winter is a good time to do that while it's just sitting in the shop. It's just that since it works ok to 3200rpm I assumed it wasn't the tach.

If you don't notice a miss or plug fouling, chances are it's just the tach. Something else to try, run a new tach feed wire outside the loom to your tach and see if that helps. I've seen EMI effect signals before, although never in a tach.

Are you sure your tach is set for 8 cylinders,( most tachs are for 4,6,and 8 cylinders) should be a button on the back of tach to change settings

Should not make it act funny, just gives you a wrong rpm reading.

Thunder, I've had a very similar problem. I have a 540 Gen IV with a Thunderbolt ignition system. I had the shop replace all the gauges. The tach would work at low RPM's but would crap out at higher RPM's. An old tach from the shop worked perfectly. The gauge was sent back to Gaffrig 2x. They claimed it works perfect. I got fed up and just ordered a color matching bezel to use on the "shop tach" that was put in temporarily. It's frustrating paying not only for the new equipment, but to have it installed, (and reinstalled) and it still didn't work. I guess sometimes "new" isn't "better", I give Gaffrig an "F".