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Voltage at my coil is 13.4?

Sonny

It’s all fun til the rabbit gets the gun.
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I am installing a new MSD distributor ready to run in my 70 Belvedere with a 440. I have removed the electronic ignition, ballast, etc. and just have a standard points wiring set up (as pictured). However I am getting 13.4 V at the coil when the engine is running, and 11.8 when the engine is off but in the run position. Doesn’t that mean the voltage regulator is bad? The engine has never ran better, but I want to confirm that voltage before driving it.
 
The voltage the alternator puts out can go up to 14.5 volts or thereabouts.
It depends on what is drawing current and the state of charge in the battery.
 
The voltage the alternator puts out can go up to 14.5 volts or thereabouts.
It depends on what is drawing current and the state of charge in the battery.
So any voltage under 14 or so won’t hurt the coil?
 
Correct the coil will not be worried by an extra volt or 2.
If the regulator is faulty and over charges the battery that can be no good but from info in your post I believe you are ok.
 
All mine have hit in the 13’s while running. I’d say your good
 
View attachment 725830 I am installing a new MSD distributor ready to run in my 70 Belvedere with a 440. I have removed the electronic ignition, ballast, etc. and just have a standard points wiring set up (as pictured). However I am getting 13.4 V at the coil when the engine is running, and 11.8 when the engine is off but in the run position. Doesn’t that mean the voltage regulator is bad? The engine has never ran better, but I want to confirm that voltage before driving it.

I run an MSD "ready to run" model on the Mopar big block in my drag boat. When you remove the factory setup, you no longer have a resistance circuit. MSD prefers to see at least 12.5 vdc. The higher voltage is not an issue. It will vary between 13-14.5 vdc. I like the Mopar electronic ignition and run that in my car. But do a spark test on your MSD with an HP coil.
hehehe ;)
 
I run an MSD "ready to run" model on the Mopar big block in my drag boat. When you remove the factory setup, you no longer have a resistance circuit. MSD prefers to see at least 12.5 vdc. The higher voltage is not an issue. It will vary between 13-14.5 vdc. I like the Mopar electronic ignition and run that in my car. But do a spark test on your MSD with an HP coil.
hehehe ;)
That's down right shocking...
 
13.5 volts it should be the nominal voltage but can change between 13 and 14.5 as mentioned according to the battery charge/discharge status and terminals conditions where you check it
 
I also use a MSD RTR distributor, c.w. a MSD Blaster SS coil.
I ran a wire direct from battery, through a relais that powers up through the ignition switch and feeds battery direct (and charge direct from alternator) to the coil + and gives same voltages you describe.
Specially after you just started the car the alternator will give a good amount of juice to charge that battery, once that is around full the voltage will drop a bit.
Normal 12v charging can go up to 14.5 volt, the coil will be able to handle that as it is common voltage for automotive industrie.
 
Having 13+ volts at the coil is fine because the coil just steps up the input volts to about 20 to 40 thousand output volts. The coil really doesn't care if you have 7 volts or 14 volts. However, you care because lower volts means it takes longer to get fully charged and it also means more watts/amps must be pushed to met the demand over lower volts and that burns up undersized wiring.

The ballast resistor was there to protect old point style distributor because 7v made less of a spark than 12v. The design starts to have issues over 5k RPMs because the coil can't fully charge before the next spark request.

Funny story, last years I had my ballast resistor backward which meant I was getting just 5 volts to the coil. The resulted in my engine was falling on it face over 4,500 rpms. Fun times!
 
Do the same test to the battery with engine off then on.Should be about the same.
These HO ignition system also won't fire if the voltage falls below 9/10 volts.Don't ask me how I know:rolleyes:
Lastly always make sure your cap and rotor are in good shape.My heap died while driving down the pike last year.Everything looked good,,,,,,spark to the cap and nothing to the wires.

9.30.184 (2).jpg 9.30.185 (2).jpg 9.30.186 (2).jpg
 
Having 13+ volts at the coil is fine because the coil just steps up the input volts to about 20 to 40 thousand output volts. The coil really doesn't care if you have 7 volts or 14 volts. However, you care because lower volts means it takes longer to get fully charged and it also means more watts/amps must be pushed to met the demand over lower volts and that burns up undersized wiring.

The ballast resistor was there to protect old point style distributor because 7v made less of a spark than 12v. The design starts to have issues over 5k RPMs because the coil can't fully charge before the next spark request.

Funny story, last years I had my ballast resistor backward which meant I was getting just 5 volts to the coil. The resulted in my engine was falling on it face over 4,500 rpms. Fun times!
 
Can someone tell me just what is the correct voltage to the coil running and just with the switch on. using the mopar ignition on a 73 dodge charger. I checked the coil with switch on and I got 5. some volts, with the car running I saw 7 .25 alternator charging 14.85 volts.
 
I run an MSD "ready to run" model on the Mopar big block in my drag boat. When you remove the factory setup, you no longer have a resistance circuit. MSD prefers to see at least 12.5 vdc. The higher voltage is not an issue. It will vary between 13-14.5 vdc. I like the Mopar electronic ignition and run that in my car. But do a spark test on your MSD with an HP coil.
hehehe ;)
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:D
 
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