Thread: What coil to use with an early V8 electronic distributor?

Hi
I was a bit concerned for a while about my electronic ignition too because I imported it from the states and didnt want to kill it. Since then I worked a few things out and i'm reasonably happy about it now.

Anyhow what I belive to be correct is you need a coil that matches the voltage of your ignition unit and your V8, (I have a Rangie). If you can find documentation for your ignition unit it should tell you what voltage range it's happy to run at. I was lucky to find out mine runs 9-18v.

The coil is the thing that confused the hell out of me.
My V8, (while running) should run at 9v. An un-unballasted coil (mine is un-ballasted) usually runs at 12v so it needs a ballast resistor to reduce the voltage down to 9v. If your coil is the original coil it might be "ballasted" ie have a ballast resistor built in or have a ballast resistor "in-line" to the positive terminal. If it ballasted it might say on the coil.
I bought the wrong coil originally so I fitted a resistor.

To try and summarise or even just not to confuse myself:

• Your ignition unit needs to be happy running at 9v, (although at start up I think it jumps to about 12v).
• To replace your coil get a ballasted coil OR an un-ballasted coil and fit a ballast resistor inline to the + terminal getting a ballasted coil is easier, less connections, cheaper.

Here's something you can do, once you fit your coil, with your engine running put the negative tip of a voltage meter to ground then the positive terminal to the + terminal on your coil if it's about 9v you are OK. If it's much more fit a resistor if it's less hmmm well that's another problem I guess. Mine runs about 10v which I think is acceptable.

If you are getting a weak spark you can check your HT leads with a voltage meter I think they should read 5ohms but I can't remember for sure. I'm sure someone will put me right. It could equally be timing, poor rotor arm/button, distributor cap etc

Good luck with the coil though...

Steve

I'm not sure there is such a thing as a ballasted coil - my understanding is that there are coils which are designed to be used with a ballast resistor and those which arent. There are also coils which are designed solely for electronic ignition systems.
The purpose of the ballast resistor is to reduce voltage across the points and thereby prolong their life. 12v is supplied direct to the coil to boost spark during cranking only and make starting easier when the engine is running, the coil runs on about 9v. However that is relevant to a points system only. Some points systems use a ballast resistor, some dont, depending on the vehicle.
With an electronic system, there are no points to protect and using a ballast resistor should be unneccessary. I'm not sure that I've seen a ballast resistor used with an electronic system.........
After fitting the electronic distributor, I've done away with the ballast resistor and the wire that used to supply 12v only when cranking is now obsolete.

Hi
Ahhh sorry i skimmed your post and must have been sleepy I though u swapped out to electronic points/ignition not your whole distributor.
My electronic ignition is a add-on unit that gets rid of the points but keeps the old distributor, cap and rotor arm. That's why mine still need a resistor.

Yes you can get a ballasted coil. I just loaned one out to a bloke who blew his coil on a run and it has "Ballasted" printed one it. Maybe it's just an old time thing??

As for a coil for your system you might be better off asking those with a newer rangie after they changed to all electronic.
Maybe a thread title of Coil for electronic ignition, which one? might work better?

Im going to try your suggestion of a new thread title.

I think the question and replies above show some confusion.
The issue of ballasted vs non ballasted is not DIRECTLY relevant to the ignition sytem. It is related to whether the car maker decides to have a boost to the coil for starting to counteract the voltage drop of the starter.
Most if not all cars with ballast resistors wil have 2 wires to the coil, one for starting ( which bypasses the resistor with 12 volts), one for running with 7-8 volts.
All Rangies AFAIk have a ballast resistor coil, and most old ones do not have a big resistor( rectangular pottery thingo, but have a resistor wire from the IGN switch.

The issue of the type of coil to use with an electronic ignition depends on the ignition type.
The simple aftermarket transistor switch like a Luminition needs a points type coil, as the current demand of a points coil is less than a "high Energy" electronic coil.
A High Energy ignition as fitted to 3.9 can run a transistor ignition coil , which drags far more current, and produces more volts.
However The coil must be matched to the ignition.
For example , I was told by Bosch technical assistance that a 727 coil should not be used with the 3.9 amp. I now have aBosch/Mitsubishi amp which I got with my Unichip, and thiscan run a 727 Transformer coil.
however someone on this forum has been running a Disco for years with a 727 so go figgure.
It does not matter whether the coil is aballast resisitor type or not as long as it is matched firstly to the circuitry in the car, and secondly the coil is the correct type( points vs high energy)
PS I have a Bosch electronic coil from a 3.9 .I can give you the number, but they are obsolete from Bosch anyway. I do not know 100% whether the 3.5 and 3.9 ones are the same but I think they are. If you are in Sydney and can pick it up from Avoca Beach , you can have it.
Regards Philip A

it's a bit odd this coil resistor thing. I ran mine with replacement electronic points and a rotor arm but with a high "hight energy" non ballasted coil for over a year. It ran fine and started great. I added the resistor and it's made no difference what so ever. It's just one of those peace of mind things and with luck my dizzy cap & rotor arm will last a bit longer.

edit ***
hmmm now I come to think of it that dizzy cap & rotor arm have been fitted for about two years now. So it's not doing too bad.

It MAY be OK , but you are running something that is meant to run on 8volts on 12volts.
This usually causes a lot of heat and a short life.
If you have a Luminition or similar you are very lucky that your coil has not blown the output transistors.
After asking the distributor, who said "well its not really recommended", I fitted a Bosch 727 to my Luminition equipped car. It lasted about 30 seconds before the Luminition was toast.
Inside the box of the new Luminition was the warning "WARNING < DO NOT USE HIGH ENERGY COIL"
Live and learn.
Regards Philip A

Originally Posted by PhilipA

with ballast resistors wil have 2 wires to the coil, one for starting ( which bypasses the resistor with 12 volts), one for running with 7-8 volts.

my Rangie only has one wire to the coil and if i remember right it runs 12v all the time, (Hence fitment of a resistor).

Am I missing a wire?