The Stovebolt Site Forums The Shop Area The Electrical Bay Pertronix flamethrower coil

I have a 40,000 volt flamethrower coil on order to go with an existing pertronix ignitor in the dizzy. Do I wire this coil with or without the ballast resistor. Their website gives diagrams for both, but I don't know which way to go. It's a 12v system on a 58 235 in a 54 1/2 ton

The ballast resistor is to save the points from burning up on 12 volt sys. you have a pertronix so you would not need it.

Pete

maybe that's been my problem all along. When I get my waterpump back from the rebuild shop I'll put it back together and try bypassing the resistor . Thanks

Like Pete said, the Pertronix unit requires 12v, just remove the resistor from the truck, put it on your work bench, and wire that unit with 12v.

Dan

wes,

I have been using 12v 235/261 Pertronix ignition and Flamethrower coil for over 10 years with no ballast resistor. I had called the Pertronix Technical Support about this and, after a long conversation with two people, they concluded that no ballast resistor would be necessary.

However, since that time, more than a few people have reported that Pertronix Technical Support has informed them that a ballast resistor was necessary in a 12v 216/235/261 application (with or without their Flamethrower coil).

Just to add to your (and our) confusion, look at page two of these installation instructions. It seems to indicate that if you had a ballast resistor with your points, you would keep the ballast resistor when using the Ignitor.

Well you're right about the confusing part. The red wire is 12v,because it's prior to the resistor. Then the black wire would be reduced voltage,using a ballast resistor or coil with internal resistance.
It's been 5 years since I hooked mine up and at time I also ordered their coil. I didn't make note of weather or not that coil had internal resistance, just hooked it up using no ballast resistor.
From what I see, it would be necessary to use a coil with resistance or a ballast resistor.
Neswes, to answer your question, Don't use the ballast resistor if the coil has internal resistance.
Now, does that flame thrower have internal resistance, don't know, but my guess would be yes, but you will need to determine that.
Tim, thanks for pointing that out.

Dan

Since your truck has a 12 volt electrical system, I would stay with a ballast resistor for your electronic ignition system unless the coil has internal ballast resistance. The original contact ignition system and front-end wire harness was designed to operate with a steady-state (static) primary current of 4-5 amps with a ballast resistor and about 1.5 ohms of coil primary resistance. Static current is the steady-state current flow that results from the system voltage and system resistance, but does not consider the brief opposition to current caused by inductive reactance in the coil as primary current rises after turn-on. The importance of this point is that the ignition system reaches the static current level when the coil primary winding has reached magnetic saturation, which occurs near the end of the dwell period, but occurs earlier at low engine speed- below about 1500 RPM. Now, if you leave out the ballast resistor, you will increase the primary static current, approximately double, to steady-state of 8-9 amps. The wire harness will probably handle that for short-trip driving, but prolonged engine operation (several hours) may result in the front-end wire harness overheating. This heating condition would be aggravated if the Pertronix system increases the dwell angle from the original 30 or so degrees. Increasing the dwell angle increases the time interval during which primary current flows, which in turn increases the power (heat) dissipated by wire resistance. So I guess the short version of this is that if the coil primary resistance is around 1.5 ohms (or less), I would advise using the external ballast resistor. Coil primary resistance of about 3 ohms indicates internal ballast resistance, and you could do without the external resistor.

All this leads to some points, mostly of academic interest:

First, the only ways to raise coil secondary output voltage are to increase the primary magnetic field strength, increase the number of windings in the coil, or both. Increasing the primary field strength is typically accomplished by reducing the primary resistance, which increases primary steady-state current (and heat dissipated by wire resistance). Increasing the secondary windings in the coil then will get you a higher secondary voltage available and higher spark current (and more erosion on the spark plug electrodes). Usually, but not always, high-output coils use the combination of lower primary resistance (1 ohm or less) and higher secondary resistance- usually more than about 20 K ohms.

Secondly, and more of academic interest, is that the Pertronix system appears to be a “hot-coil” design, which is the same as a standard contact ignition system. “Hot coil” means that the coil is connected directly to power, and ignition current switching takes place on the ground side (as with a contact system). Hot-coil systems are the most common electronic ignition systems, but in the early days of electronic ignition systems, there were “cold-coil” systems, in which the current switching took place on the power side of the coil, and the ground side of the coil was connected directly to ground. There was an early Delco-Remy system of that type, and I believe there was an early Ford system also of that type- not sure about the second one.

I realize all this goes beyond the original question, but maybe this helps explain why things are the way they are.

Harvester

Any Petronics I have installed shows the resistance being used in the intruction sheet. I have always wired it that way.

This is all lots of good info but right now I'm only interested in getting my new motor to start right. Justs starts and dies mostly. I was only thinking along the lines of the starting circut because I'm not yet convinced that the issue is carb related. tomorrow I will have the water pump back on the motor and I can try my little test of starting it without the resistor. If I fry the coil " oh Well" I've got a new one on the way and I will have learned a lot.Thanks for all the input. I'll let you know what happens.

The page of questions and answers 3rd one low voltage problem ,bypass the resistor ,no need for resistor with electronic ign. sys.Lower voltage into the coil lower voltage out to the plugs.Thats why alot of people bypass the resistor for start up and switch to resistor on run to get easier start and not burn the points up on the road.

Pete

Hey Harvester, All that being said, can you shed some light on why one way was used over another or v/v ?
Mopars were big on a ballast resisters and didn't GM use a primary resistance wire and that would be with a coil with no internal resistance, right ?
What I'm wondering is why the different approach or the pro and con of either.
Correct me if I'm wrong, but you use 2 different ways to accomplish the same thing, right ?
1- Ballast resister, no internal coil resistance.
2- No ballast resister, coil with internal resistance.

GM using a resistance wire in place of a ballast resister.

These are not facts, only what I think or currently believe.
Dan

Dan,

Your understanding of the resistor/no resistor is correct. The harness/loom resistor that GM settled on in later years replaced the external ceramic block type of the early 12 volt days. I never heard it said by anyone at GM, but I think harness resistor wire was cheaper, and maybe more durable than the ceramic block. Otherwise the voltage-dropping function is the same. I seem to remember that early Ford 12 volt systems had an external ballast resistor that used fairly fine wire for the resistive element, and was contained in metal housing. It was attached to the ignition coil, or close to it. I remember that type being prone to failure (but now we're in the realm of foggy memory and ancient history). The ceramic block that GM and Chrysler used was an improvement over the Ford type, but they were still more prone to failure than the harness type.

Some Chrysler products, and I think a few Delco-Remy ignition systems for non-GM appications, used a coil with internal ballast resistance, but those had a tendency toward hard starting in severe weather/low battery conditions. I think that was what led Chrysler (Electric Autolite/Prestolite) to switch to an external ballast resistor and a non-resistor ignition coil. The later Chrysler external ballast resistors had two resistor elements side-by-side, one for the ignition circuit and the other for their electronic voltage regulator (I think). The two elements had different resistance values, and it was a common mistake to connect the wires incorrectly when replacing the dual resistor part.

It was also a common mistake to replace a coil with the wrong type- non-resistor coil with a resistor coil, or vice-versa. Sometimes it took a while to sort out why the car was hard starting, seemed to have short spark plug life, or point life was only a couple of thousand miles.

Hope this helps.

Dean

Coils with built in resistance have more windings then ones built for external resistance. They are for tractors & other low rpm engines. There is no coil with a built in resister.

I have installed the Pertronix Ignitor II along with the flame thrower to my 1955.1 3100 truck. I checked the coil and it shows 3.4 ohms and all the connections have been double checked.
Do I need to change the plug wires from stock or are they OK. The engine will not start. I set the gap on my plugs but have not been able to time it as I can't get it started. I checked the timing mark and it is right on the pointer at the number one plug.
Frustrated

Have you removed and re-installed the distributor since the engine last was running?

My instruction with ignitor II with flamethrower coil was to remove the resistance wire and use regular wire on my GMC 270. Runs great. Good luck. Jim

flyn55: When you set the timing mark at the pointer, pull the valve cover and make sure that both rocker arms are free om #1. If you have a valve compressed then you need to turn the engine one more complete revolution to get to top dead center. The cam turns 1/2 the crankshaft and the mark on the flywheel will line up at both T.D.C. and, when the exhaust valve is open. Just the nature of the beast. We have all done it and it is easy to fix. When you are certain that you have #1 at T.D.C. and on compression then it should start. It will run just fine with the valve cover off. If you are om level ground you will not have a big mess unless there is something wrong. If you have oil spray then something is wrong and you need to fix it any way. As a bonus, you can see that oil is at the rockers and if any push rods are bent. When it starts run at a fast idle for a while and keep an eye on the oil pressure. Let it warm up and then set the timing and final adjust the valves. If you still have trouble starting then look for spark, fuel, and compression, as always. Have fun and some luck won't hurt ya any ways.

Sorry about the m and n thing, I gotta edit the thing before I post,

Thanks for the help. After sleeping on it I found that the timing was so far off that it wouldn't start. I took the distributor cap off and after lining up the timing mark I found the rotor was not aligned with the number one plug. After realigning it started. I had to time it by ear as the mark was out of the window. It seems that the setting for the timing is such that I can't see the mark with my old timing light.
The old coil had an internal resistor so I just put the new Flame Thrower on and all is well so far.
Thanks again