My 312 has a Mallory Dual Point Dizzy with the Mallory coil.  I just bought a new Bosch Tachometer looks like the Sun Pro of the seventies.  Hooked it up to the negative terminal of the Mallory Coil
Seems like the RPMs are reading double.  I am thinking I should switch the tacho's setting to 4 cylinder.
Any thoughts on this.
Thanks,
Richardii

I have a 312 with a Holley Rotovance dual point, a Marchal coil and a 60's era Advanced Instruments tachometer. My tach is set for 8 cylinders and works/read fine. Maybe a difference in distributor lobe design.

My old Mallory Dual Point had a 4 lobe cam and I used a mechanical tach but I would think you need to set it to 4 cyl if it has two sets of points and a 4 lobe cam inside.

  Vic Correnti

My Bad: I opened it up and the switch was set a four not eight. I think when I stuffed it into the cup the wires might have rubbed the switch.
Thanks for the imput