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Old 04/25/12, 11:20 AM   #1
ObscureMachine
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MSD Coil. Need a ballast resistor?

MSD Blaster 2 coil, with Pertronix ignitor. Instructions say I need a ballast resistor. Do I really need one?

thanks,
-jim

Last edited by ObscureMachine; 04/25/12 at 07:59 PM..

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Old 04/25/12, 11:37 AM   #2
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No - all MSD coils are full 12v I believe. I do not have one.

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Old 04/25/12, 11:42 AM   #3
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This info is direct from MSD. Even though specified when using their ignition system general rules should be followed. See were they reference coil only.

If the coil instructions specify the resistor, you should use one. Available at any automotive store. The coil should also be mounted upright with a short as possible coil wire.

Ballast Resistors.
When using an MSD 5 or Blaster Ignition, if a ballast
resistor was originally used in the coil wiring, it should be bypassed.
If a ballast resistor was not used, it is not necessary
to install one. When an aftermarket coil is used with the
Blaster Ignition or MSD 5, follow the coil recommendation
for a resistor. A factory ballast resistor does not need to be
bypassed with an MSD 6, 7, 8 or 10 Ignition

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Old 04/25/12, 11:48 AM   #4
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Official instructions from MSD at Summit.

WIrIng to a Stock PoIntS IgnItIon
1. Connect the negative wire to the negative terminal (-).
2. Connect a wire from the coil positive terminal to one side of the ballast resistor. Connect 12 volts to the other terminal of the resistor.
3. Install the high voltage coil wire.

But this is for points. I have the Pertronix ignitor.

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Old 04/25/12, 12:27 PM   #5
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Then you don't need the resistor. The ballast is to minimize burning the points. You will be fine without it.
I have the Pertronics II and accell super coil and have had with and without MSD6 box and no resistor. Have never had a problem. When i had dual points, i was changing more often without the resistor.

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Old 04/25/12, 04:06 PM   #6
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Thanks Dave. That's what I needed.

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Old 04/25/12, 06:05 PM   #7
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The resistor is so you dont blow up the coil when the power is on. Doesnt matter points or electronic. Yes points need a little more resistance so there resistor has more ohms. Basically unless you run a MSD setup you need a resistor thats why they say that specifically. MSD setups dont have the coil wired directly from the igintion switch it runs through there ignition box first. There are very few coils that dont require a resistor and most that dont have one built in already. Pertronix setups still need a resistor unless you run there coil (which probably has one built in already) Its just you have to wire the pertronix box to have a full 12 volts so you cant run it off the resistor wire feeding the other brand of coil.
Basically you need to have a ballast resistor on your setup thats why MSD has it in there instructions.

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Old 04/25/12, 06:18 PM   #8
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Quote:
Originally Posted by broncnaz View Post
The resistor is so you dont blow up the coil when the power is on. Doesnt matter points or electronic. Yes points need a little more resistance so there resistor has more ohms. Basically unless you run a MSD setup you need a resistor thats why they say that specifically. MSD setups dont have the coil wired directly from the igintion switch it runs through there ignition box first. There are very few coils that dont require a resistor and most that dont have one built in already. Pertronix setups still need a resistor unless you run there coil (which probably has one built in already) Its just you have to wire the pertronix box to have a full 12 volts so you cant run it off the resistor wire feeding the other brand of coil.
Basically you need to have a ballast resistor on your setup thats why MSD has it in there instructions.
Okay. That helps. Sometimes the simplest things are complicated for me!

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Old 04/25/12, 07:42 PM   #9
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Quote:
Originally Posted by broncnaz View Post
The resistor is so you dont blow up the coil when the power is on. Doesnt matter points or electronic. Yes points need a little more resistance so there resistor has more ohms. Basically unless you run a MSD setup you need a resistor thats why they say that specifically. MSD setups dont have the coil wired directly from the igintion switch it runs through there ignition box first. There are very few coils that dont require a resistor and most that dont have one built in already. Pertronix setups still need a resistor unless you run there coil (which probably has one built in already) Its just you have to wire the pertronix box to have a full 12 volts so you cant run it off the resistor wire feeding the other brand of coil.
Basically you need to have a ballast resistor on your setup thats why MSD has it in there instructions.
Yes. You are correct BUT it will depend on the coil type. with the MSD Blaster II coil that the OP is using it doesn't require one with a breakerless ignition as is with the Pertronics. With points the coil can be damaged but is more evedent with a less inferior OEM coil. Some aftermarket coils have a higher primary resistance specifically designed for use with a points only system without a external ballast.

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Old 04/25/12, 08:14 PM   #10
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Ack! I have researched and everything says either yes or no. I guess I'll call pertronix tomorrow.

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Old 04/25/12, 09:14 PM   #11
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Obscure. You don't need it.

The ballasts only function is to reduce the primary voltage after the vehicle is started (or key "on" position) to minimize excess voltage to the coil and points in a "POINT" system.

Read the last sentence in the description.

http://www.msdignition.com/Products/...rformance.aspx

They also tell you to check with the ignition manuf.

http://www.pertronix.com/support/man...itor12vneg.pdf

Pertronixs gives you wiring examples for both and also states a "points" type coil is required which your MSD blaster meets those requirements.

You can put one in if it makes you feel more comfortable but isin't REQUIRED.

I have run the same setup for over 20k miles with no coil failure.

When you reach the end of your rope, tie a knot in it and hang on.
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Old 04/25/12, 09:37 PM   #12
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Here MSD's words "Most late model vehicles with electronic ignitions do not require a ballast resistor, check your ignition and manufacturers specifications to determine if a ballast is required in your application."
Reason becasue the ballast is built into the factory wiring already. or the aftermarket system powers the coil. Pertronix doesnt do that it only tells the coil when to fire(just like points). hence the power feed straight to the coil from the igintion switch.
The pertronix needs a full 12 volts to power it you dont wire the coil to the pertronix the coil is powered seperately with a ballast yes aftermarket coils tend to be a little better than stock coils and may not blow up as fast but do you really want to take that chance. Few coils can handle a full 12 volts for long especailly if the engine is not running..
As was stated contact manufacturer in this case MSD as its the coil your worried about.
While it may never blow up without a ballast resistor your taking a chance. So its up to you.

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Old 04/25/12, 09:59 PM   #13
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Quote:
Originally Posted by ObscureMachine View Post
Ack! I have researched and everything says either yes or no. I guess I'll call pertronix tomorrow.
Best suggestion possible!

Even if the coil can handle full 12V, the resistance may be too low for the eletronics to cope with. Ask the ignition supplier for there advise.

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Old 04/26/12, 06:33 AM   #14
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Let us know what you find out, strangely I'm kind of running into he same question right now, yesterday I discovered I actually had a working coil wire on the harness, but I made one as well, so now I got 2 and don't know which is better. Your question makes me wonder if I need either.

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Old 04/26/12, 09:32 AM   #15
ObscureMachine
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I bought a ballast resistor with when I got the coil, but then I did something stupid. I started reading and researching, when doesn't seem to clear things up very often.

I'll call soon.

1974 Bronco Sport, 302, Some stuff, Some round things,
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