I recently installed a 300 into a 1962 4WD. The distributor on it has a 12v Pertronix igniter, and I just bought a Pertronix 12v 3.0 ohm coil to replace the old coil. . I do not know if this set up requires a ballast resistor in line or if a 12v 3.0 ohm coil has an internal resistor wtin the windings...Therefore do I need an external resistor. ? Can someone clue me in? Tom

 

These should have been in the box with the coil.

 

Have you tried calling Pertronix? They have an excellent 1-800 tech line, and lots of data on their website.

Which Pertronix Ignitor? They have at least three that I know of. The basic Ignitor 1 module wants at least 1.5 ohms in the primary ignition circuit itself. What this means is the ultra-high output low ohm coils like their 0.6 ohm FlameThrower, will burn up the simple basic Ignitor 1 module.

Ohms Law is your friend here. Pencil it out no matter what you're using and see what the current flow is.

The Ignitor 1 is limited in the amount of current or amperes it can tolerate to around 8 amps. The contact points of yore averaged around 3 amperes while the engine was running, right at the edge. If you left the key on without the engine running, it was closer to 4 or 5 amps, and if the points just happened to be closed - they would burn up. They used a divider network at the switch and starter relay to bypass the ballast resistor during engine START, for a bit hotter spark with full battery voltage. A few seconds was OK.

Anyhoo, a 3 ohm coil will work OK with the Ignitor 1 but the spark output may be attenuated. I've ran a nice heavy direct wire (ballast wire deleted) to a 1.5 ohm Flamethrower coil and the Ignitor 1 w/factory generator charging system for about 20 years now and it works great with full battery (charging system really) voltage.

What you'd be doing here is sort of simulating the ballast resistor full time, even though it isn't really necessary or desirable. Call them and ask, and see what they say.

I have a spare 3 ohm Bosch blue coil stashed in case the Ignitor dies on the road, and a spare distributor setup with points. Converting back to points on the side of the road isn't quite as simple as it might sound on paper. I'd lose the extra juice supplied at START but it should be OK otherwise and would be a quick swap.

 

Yeah, I wish there was some paper in the coil package... but nope. I bought this engine on CL and the PO just said it has a Pertronix ignitor. I’ll probably pull the cap and see if there is a part number on it. He said it was about 10-12 years old. That’s all I know.
About 20 years ago I installed one in my 1957 Ford 800 tractor. I was having difficulty getting the motor to time after installing it and it was giving me fits. I posted my trials on a tractor website. Guess what? The owner of Pertronix called and was upset that I posted my issues online for everyone to see. He was not a nice guy about it. I was reasonable in my posting and not on a rant. Never wanted to call em back after that...and didn’t want to do business with them too. But this engine has one and felt a compatible coil would be best.

 

A V8 wants at least 1.5 ohm coil. A Six cylinder wants a 3.0 ohm coil with Ignitor 1, I expect that's what is installed, but .. ya never know.

The module itself should have a sticker with a part # on it, try to sniff out what flavor Ignitor is installed. The Pertronix website has a pretty extensive FAQ and troubleshooting section. Use that to your advatage.

Make sure the engine ground cables and connections are clean, and tight, Pertronix further advises to measure the resistance between the negative battery post and the distributor breaker plate, to not exceed 0.2 ohms.

The distributor needs to "see" a good solid low resistance ground reference. This same test is performed when using breaker points as well. Paint (for example) on the engine block where the distributor housing mates might interfere with a good electrical connection between the ignition distributor and engine block.

Sometimes, people might even leave out that non-insulated bare copper stranded ground wire inside the distributor. This is what grounds the breaker plate (and the points, or the electronic module) to the distributor housing, it is important that this wire is present and it isn't corroded, frayed etc.

Subtract the ohmeter lead resistance from your measurement to arrive at the distributor breaker plate to battery post resistance figure.

 

I think the odds of whoever taking the call on the Tech line will somehow realize you're the guy the boss was pizzed off at (20 years ago) are pretty dang slim. Call them with the part # and they will explain it to you all over again.

Figure out what Ignitor module is installed or it's just a guess and by golly, or go back to points maybe?