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Pertronix and Factory Tach
#1
Hi All,

Several threads out there on this topic, but didn’t come across one with a clear answer to these questions. When running a Pertronix 1 and a factory tachometer ...

1. Does the tach require use of the red/green wire with resistance from the ignition to the coil for proper function? A 12V source will not work and/or will damage the tach? Or, does the voltage going to the coil not matter for tach function?

2. Does the Flamethrower coil require a full 12V input to function as they suggest, or will it work off the voltage from the red/green wire?

I currently have the P1 running off switched 12V power, and a stock coil using the red/green wire. I’m considering going to a Flamethrower coil, but need to understand how this would need connected for both the coil and the tach to function.

Thanks!
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#2
i'm using a pertronix ign sys. i didn't do anything with the wiring, no changes.. orig coil and just wired in the pertronix to the resistor wire as the points were using.
my tach works and engine runs great even with the reduced voltage. my understanding is if u use 12v to run your new ign sys and don't use the resistor wire the tach is dead. if u don't need the tach then by passing the resistor wire from the ign sw to coil work also.
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#3
I had to run a switched 12V from a pigtail off the fuse block extra slot. Bypassed the resistor wire behind the instrument cluster, and sent my tach out to have it upgraded to modern tach wiring. I want to say RCCInnovations on this sight did the work. Now everything works awesome!! I run the P2 with Mallory coil and all is well!!
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#4
(07-30-2018, 06:01 AM)cheezsnake Wrote: Hi All,

Several threads out there on this topic, but didn’t come across one with a clear answer to these questions. When running a Pertronix 1 and a factory tachometer ...

1. Does the tach require use of the red/green wire with resistance from the ignition to the coil for proper function? A 12V source will not work and/or will damage the tach? Or, does the voltage going to the coil not matter for tach function?

2. Does the Flamethrower coil require a full 12V input to function as they suggest, or will it work off the voltage from the red/green wire?

I currently have the P1 running off switched 12V power, and a stock coil using the red/green wire. I’m considering going to a Flamethrower coil, but need to understand how this would need connected for both the coil and the tach to function.

Thanks!

I originally had the P1 and Flamethrower running through the tach/resistance/red green wire.  It worked fine and the tach functioned properly.  I've since switched to a Duraspark setup.  For this, I bypassed the resistance wire and wired the tach straight to the coil.  I've had it this way for almost 3 years and aside from my tach reading slightly higher RPMs, it hasn't fried it and has run perfectly fine (despite the increased voltage through the tach).

I will say, the Duraspark setup for me was marked improvement over the P1.  The car runs and drives much better.

Good luck!

Jason
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#5
It depends on which Flamethrower coil you are talking about, and what the primary resistance of the coil is. If you're using one with a primary resistance of 1.5 ohms it will be OK. Using one of the low resistance (0.6 ohms or lower) coils will require the full 12 volts.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#6
(07-30-2018, 10:11 AM)YDon C Wrote: It depends on which Flamethrower coil you are talking about, and what the primary resistance of the coil is. If you're using one with a primary resistance of 1.5 ohms it will be OK. Using one of the low resistance (0.6 ohms or lower) coils will require the full 12 volts.

Thanks, Everyone. Yes, I intend to use the 1.5 ohm Flamethrower 1 coil. So, if I understand correctly, I should be able to perform a straight swap with the stock coil, same wiring as I have, and all should be fine? If so, that would be nice and easy.
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#7
Yes, your P1 and F1 coil should be fine with your existing wiring and tachometer.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#8
Awesome! Thanks, Don.
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#9
+1,
p1 works like a charm. Installed one in the mid 90's on my 73, drove more than a decade and its still doing its work.
Its simple design is very durable.
I've already have a new one waiting for my 71.
Another plus, is that may you upgrade to EFI, all works fine with no issues.

73 modified Grandé 351C. Almost done. 
71 429CJ. In progress
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#10
Completed this project today.  Car starts and runs good.  Still needs a road test.  But, for those using a P1 with factory tach and aftermarket carburetor, I thought I’d share what worked for me. I believe the brown wire may have originally connected to the solenoid on the factory carb. I repurposed it to feed the Pertronix relay. On my car, the voltage on this wire varies from 10-12 volts, but the relay works fine. The red wire I connected to the battery post on the starter solenoid. Thanks again for all the input.
[Image: E75_DA215_273_E_43_FD_8519_9417_F524_A2_A5.jpg]
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