I would appreciate tips on the best way to get a 12 volt current to my coil verses the 9 volts provided through the factory wiring. The source needs to be controlled by the ingnition switch.

Original point system would burn-up with 12 volts but I have converted to pertronic system. I have seen previous posts but could not find with a search.


I appreciate all the great help from the members!

 

Two ways,..

1) You can replace the resistor wire with 12g twisted copper wire (white if available) all the way to the junction box on the firewall (this isn't that easy but it's a cleaner looking method)

2) On your fuse panel you'll see an available port called "Ign" or ignition. You can run a jumper (same wire specs as above) from there to your coil.

Good luck!

 

Be aware the coil is designed to operate on 9V and constant 12V will burn it out. That is if it has an "R" designation which is what came from the factory. The source marked "IGN" is perfect for powering the pertronics unit and that is what I have done. Leave the resistor wire to the coil and run the new wire just to the pertronics. You can even put a kill switch in the cct.

 

Believe it is the points that gets the 12v crank and 9v running wiring, the coil gets a full 12v all the time

 

Thanks for he rsponses, now have more ?'s.

When I turn the key on (not running) my meter reads 6 volts at the coil. I believe this is an original coil.

- Should I buy a new coil and if so do I get the enernal or external resistor?

- By connecting directly to the 12v ignition source will I pick up ignition noise in my audio system.

Thanks for the help.

 

Nope - it is the coil. Points are on the other side of the coil.

 

Another way and an easy one is tap into back up lamp harness.Its 2 wire connector Lt.Green and Pink(68-74) under wiper motor and goes down toward trans.Use the blue tap conn. that usually comes with the Pertronix.Tap into the Pink its hot with key on and fused.If you have the latest Pertronix that uses the points cam for signal be sure to pause in the "ON" position when starting for a second or two.If you go direct to "CRANK" it will take longer to fire.Leave coil wired as is -it will recieve 12 volts on cranking and aprox. 8.5 while running and follow Pertronix instructions black wire to neg.side coil.Red to keyed 12 volts.

 

You will see different readings on the + side of the coil when the points are closed vs. open. If you open the points (stick a piece of paper in them), then measure the + side of the coil, you will then see the "dropped" voltage to them.

The resistor has nothing to do with the radio "noise". Originally, there was a filter capacitor connected to the coil + side (case of the cap. was grounded) - that was to help with the radio noise.

As others have said, if you connect the coil to a 12V source and it is supposed to have a ballast resistor, then you will burn it out.

If you are going to stick with a stock configuration, then you should get the "correct" part and use the ballast resistor (wire). If you go with an aftermarket coil, then do what you want, but follow the directions of the specific coil.

Are you trying to fix a problem?

 

Just go HEI. More reliable, if it breaks down parts can be had anywhere, etc.

 

There's been several things tossed out in this thread. Some make sense, some don't. I don't know the internal specifics of the pertronics unit (I converted my stock tach drive distributor to HEI electronics twenty years ago. It's bulletproof and inexpensive), but there are a few basic rules to remember:

1) Everything runs off 12 volts. You'll only read nine volts if you get a voltage drop from current flowing through a resistance.
2) If the Pertronics unit is halfway intelligent it will control the dwell time and current, so a ballasting resistor is probably not necessary. If it is a simple electronic switch that cannot distinguish if the engine is turning (will it turn on coil primary current and hold it there like a set of points if the engine stops turning?) then a current limiting ballast resistor is most probably advisable to reduce the power dissipation in the coil and module. An HEI type conversion will control actual dwell angle and dwell current, so no resistor is needed or desired. I don't know what the capability of the pertronic unit is.
3) Make sure you have 12 volts not only during run mode (obviously)but also during cranking. This simple concept has caused a lot of no-start confusion with distributor conversions.
4) If you modify the voltage source to the ignition it is advisable to provide some sort of fused protection. I've never had a wiring harness fire, but it doesn't sound like fun. The specific hookups are up to you.
5) Electronic switches will shut off the primary current much faster than points will (a good thing). This may cause additional noise in your stereo system though. A capacitive filter on the coil plus side will help filter out this noise.

Good luck with your conversion. I haven't messed with a set of points since my twenties, and I don't miss them at all (the points, that is. I DO miss my twenties though.)

 

Which is exactly how the coil is hooked up in a stock points system.

 

On converting to HEI, what did you use for ignition shielding? I agree that HEI is the way to go, but I can no longer use stock shielding. Do you just decide to leave yours off?

 

Is this a 77 or a 67 ? Your profile says 77 it should have HEI.

 

And your point would be?????

 

Mine has the original shielding on it. It's a big block, so all I have is the chrome rectangular box. The points (in the original tach drive distributor) were swapped for a variable reluctance pick up coil, and the four terminal HEI module I'm using is mounted to a small heat sink under the shielding. Looks 100% stock, but absolutely bulletproof.

 

That a points coil doesn't run on 12v.

 

Wrong. Your system voltage is 12 volts, set by the battery and alternator. An HEI system has the coil tied directly to a low impedance 12 volt source because the HEI module controls both the dwell time and the coil primary current. The primary current is controlled by a module internal transistor that switches to a current limiting linear mode when about 5.5 amps are sensed passing through an internal sense resistor. Hence, the coil will charge up quickly, but be protected from overcurrent by the internal transistor.
A points system, being simple and crude, must rely on one of two things to survive. It must be incredibly big and finned to survive the high currents that may go through it, or it can have a resistor in line somewhere to limit the primary current to a reasonable amount that won't let the points or coil burn up if you turn the key on with the points closed. There's generally, I said generally, about three ohms in the system somewhere. It may be evenly divided up by a ballast resistor and the coil primary winding resistance, or just the resistor. The points don't care either way. Twelve volts divided by three ohms gives us four amps primary current. (If you know the winding inductance you would also then be able to calculate how much energy you are putting into the coil.) The designers know how much steady state DC current the points and coil can handle at zero RPM and hot conditions, so they specify a series resistance that will protect the components.
As I stated earlier, the GM HEI electronics do not need the ballast resistor to limit the peak current. The elimination of this resistance allows the coil to charge quicker, resulting in increased spark energy at higher RPMs.
I could go on, but I expect that there are a few drowsy readers out there by now.

 

You are correct sir, my bad

 

Are we talking about a points dist. or HEI ?

 

Both.