@cgsheen1 made a suggestion, Are you not willing to try it? Takes 2 minutes.

44 minutes ago, Yarb said:

@cgsheen1 made a suggestion, Are you not willing to try it? Takes 2 minutes.

Ill try it! See what happens. Right now we have the pertronix 1.5 coil installed with 1.5 ballast

2 hours ago, 72 Datsun 240z said:

The thing is my mechanic solved the rough idle and misfire after take off from long traffic by installing an msd blaster 2 coil replacing the pertronix 1.5 coil and 1.5 ballast resistor. The problem is the stock tach does not work with the msd coil which i believe is 0.7 ohms. Going back to the pertronix, the tach worls but the car runs bad.

Maybe this is the point where you decide which you want most - working tach or good running engine...

Back when I learned to drive - and for years thereafter - cars didn't come with tachometers. They ran and we drove them all over the place anyway.

(but, from the factory that car ran VERY WELL with a stock coil, a stock ballast resistor, a stock distributor, AND a stock tachometer. Just sayin')

16 minutes ago, cgsheen1 said:

Maybe this is the point where you decide which you want most - working tach or good running engine...

Back when I learned to drive - and for years thereafter - cars didn't come with tachometers. They ran and we drove them all over the place anyway.

(but, from the factory that car ran VERY WELL with a stock coil, a stock ballast resistor, a stock distributor, AND a stock tachometer. Just sayin')

You are right! Mechanic should get this engine running with pertronix ignitor module 1761, 1.5 coil and 1.5 ohm ballast.