Pertronix 3 wiring?

[Royce Peterson]

If the tach is reading low with an aftermarket coil it (the D'Arsenval movement in the tachometer) likely has lost some magnetism over the years. The stock coil has a higher resistance than most aftermarket coils that I am aware of. Higher resistance = lower current in the circuit. Lower current means lower RPM reading. The tachometer in 1967 - 68 is in series with the coil, it is in effect an amp meter that reads in RPM. 

Yes indeed. The Pertronics coil is lower resistance than the stock coil. So it gives a higher output to the plugs but ruins the performance of the tachometer.

Personally I prefer using the stock yellow top coils.

I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?

Is that were I goofed....... ?

If I swap back to my stock coil on my Pertronix I conversion, will it correct my low reading tach ?

Thanks All.

[oldcanuck]

Maybe I wasn't clear..... the Pertronix I was installed new July 2020 with a new Pertronix Blaster coil. I have run the car appx. 1000 miles since the installation.

The installation instructions included, were used. The system works well, but my tach seems to be reading 3-400 rpm low.

My question is.... if I put my previous stock coil back in, will this solve my rpm reading ?

[Royce Peterson]

The Pertronix coil is lower resistance than a stock coil so it will read a higher RPM. If your tach is reading low with a Pertronix coil installing the stock coil will cause it to read even lower. Higher resistance = lower RPM indication. Lower resistance = higher RPM indication. No it is not going to have the effect that you desire.

Why not try it for yourself? We are talking about less than 5 minutes work.

Maybe I wasn't clear..... the Pertronix I was installed new July 2020 with a new Pertronix Blaster coil. I have run the car appx. 1000 miles since the installation.

The installation instructions included, were used. The system works well, but my tach seems to be reading 3-400 rpm low.

My question is.... if I put my previous stock coil back in, will this solve my rpm reading ?

[tonys_shelby]

My thoughts are run stock coil, petronix 1. Ran this in several cars with stock tach and never an issue. No problems with enough voltage to run system even with resistor wire or tach operating properly.

[oldcanuck]

Thank you guys.... I will give it a try and report back.

BG