earlyzman

If you are still using the stock tach with a 3 ohm coil and ballast resistor, my experience was that the tach would work up to about 3000 rpm and then cut out. If I bypassed the ballast resistor it would make it to about 4000 rpms and cut out. I thought you had indicated the same symptoms in your post. After putting in the 1.5 ohm coil and leaving the original ballast resistor in the tach worked at least up to red line.

I had the exact same tach problem with the Pertronix conversion on my 72. First of all the tach is driven by current not voltage. The 3 ohm coil that you have will not drive the tach. You need the 1.5 ohm coil (available from Pertrnix) that matches the stock coil. You can leave the stock ballast resistor in the circuit which is about 1.2 ohms. The series resistance of the coil and ballast resistor is what determines the current the tach sees. You could also add one or more loops of the wire that goes through the u shaped clip on the back of the tach, but that would require a little info that I learned 40 years ago when I installed a Heathkit electronic ignition on my first Z.

I'm sure you can get that broken bolt out fairly easily. I got fooled the same way, but mine started to strip. I wasn't too worried since those bolts in combination with the locating dowells are only for the initial cam alignment. Since the head bolts go through the cam towers, they are the ones doing all the work after that. You might be able to drill that bolt and use an easy out with the cam tower in place, otherwise you'll have to pull the cam again. Good luck.

I don't know what year Z you have, but the early ones had tachs that used an inductive pick-up. Basically it is a loop of wire through metal loop on the tach. This wire is basically the conductor between the coil and the points. Now with the conversion to electronic ignition the points, if still used to trigger the ignition, has a fraction of the current flowing through them than they used to. It's not enough current to drive the tach. I did the conversion to '72 just after I bought it new with a heathkit unit. It turned out the points current was now one tenth of what it used to be. I found some small diameter wire and replaced the single loop at the back of the tach with ten loops. It worked just fine then. I'm not sure of how the Pertronix system works, but if it still uses your old points, you could do what I did. If it uses optical or inductve pick-up to trigger the system, I don't know what to suggest. I know others have said to go to a later style tach, but I wouldn't want to do that if I didn't have to. Perhaps Pertronix has some suggestions if you talk to someone with a technical background.