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By Nat Santamaria - 4 Years Ago
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I know this has been done to death. But I don’t understand why Flamethrower coil fails. Their tech support say DO NOT USE EXTERNAL resistor.
I have a 57 Tbird 312 running all stock. I do run an alternator. Output is about 14.28 volts. Holley 4160 4 barrel carb. I have pertronix ignitor 1 Module. The car runs well.
A few years I installed a Flamethrower coil without external ballast as per instructions and tech support. The Flamethrower has an internal resistor. The engine performance was much better. Better throttle response from a stop, hardly any exhaust fumes and clean plugs indicating a much better burn. The problem is the coil without the resistor gets very hot and fails. If I run it with ballast resistor it will last but defeats the purpose. Is there a voltage loss to the plugs when using a ballast resistor? If so how much.
I am currently using a MSD 45,000 V Blaster II with external resistor - again runs good but would probably get better performance without resistor.
The Brillman Company makes a coil EB30SS with 55,000 V that must be used with an external resistor maybe this is an option
Any suggestions or help appreciated.
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By Ted - 4 Years Ago
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What ohm rating is the coil? The Pertronix I modules do require using a 1.5 ohm coil while the Pertronix II modules require a 0.6 ohm coil. Using a 0.6 ohm coil with the Pertonix I module does have coil heating issues.
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By Nat Santamaria - 4 Years Ago
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I used 1.5 ohm Flamethrower as suggested by Pertronix
My current MSD coil is .7 ohm Primary Resistance 4.5 Secondary Resistance
Im not sure the stock Ford coil ohm rating
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By Nat Santamaria - 4 Years Ago
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Hey Ted
Could this coil work?
https://brillman.com/product/eb30ss-12-volt-super-stinger-external-resisted-ignition-coil/
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By Gene Purser - 4 Years Ago
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I have had several conversations with the Pertronix tech. Too low resistance (combination of coil and ballast resistance) to the Pertronix will burn the Ignitor up. He said more resistance is OK, but performance "might" suffer at higher RPM. Also, voltage rises in the coil until the spark can jump to a ground. If you have good wires and other ignition parts, reasonable (not super high) compression, and a normal gap on the plugs, the spark will never rise to the advertised voltages on the high voltage coil, usually around 15,000-20,000 volts. The OP didn't say how many Flamethrower coils have failed. If only one, maybe it was a faulty part.
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By Florida_Phil - 4 Years Ago
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My 292 has a stock 1957 Ford distributor with a Pertronix I unit. My coil is a 1.5 Ohm Pertronix Flame Thrower coil. My coil does not run hot. It has been in my car for over a year without any issues. I did have an intermittent problem with the overdrive kick down switch. I removed the wire from the switch to the coil and it has worked fine since then.
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By Nat Santamaria - 4 Years Ago
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Florida Phil are you using the Flame Thrower with External resistor?
The Flamethrower I had originally lasted about 1 year without external resistor. Great performance.
I then replaced with 2 more and they failed quickly.
If I use flamethrower with external resistor its fine but defeats purpose -
The MSD Blaster II I am currently using has been in there for 2 years using external resistor performance is good.
In short I would like to use a coil without resistor for better performance.
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By FORD DEARBORN - 4 Years Ago
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As stated above, a 1.5 ohm coil may be what you need with Pertronix 1. Even if you were to install Pertronix 2, the 1.5 ohm coil will run cooler with out an external resistor. It is very advantageous to NOT use an external resistor in favor of a hotter spark. I did some crude testing with a distributor machine years ago with ignition components wired as would be in the vehicle. The difference is quite noticeable with out the resistor. Like, could draw about twice as long of an arc, the arc is much more intense, makes more noise, and ozone becomes very noticeable. Also, because the rise time is quicker, a longer spark duration can be measured on an oscilloscope. So, yes, it's very beneficial to eliminate the resistor. Do you know if your coil is oil filled are epoxy filled? There is the possibility that an oil filled coil operated horizontally can leave part of the internal coil core not covered with heat conducting oil. For sure, there will be an air space along the length of the horizontal surface inside the canister. Just some food for thought. For that reason, I always use an epoxy filled coil just to error on the cautious side. For several years I ran Pertronix2 with no resistor and 1.5 ohm coil with no issues. Hope this helps, JEFF...........
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By Nat Santamaria - 4 Years Ago
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Ford D
I was using the Flamethrower 1 oil filled for about a year with no issues. Great performance. When it failed I replaced with epoxy filled because I noticed little drops of oil on the Valve cover. The coil sits horizontally.
None of the Epoxy lasted very long with exact same hook-up (no external resistor)
Ideally I want to use a high powered coil without a resistor to get the best performance.
Any advantage to running Pertronix II - can I then use a coil without external resistor?
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By Tedster - 4 Years Ago
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As a technical point, I hear people sometimes say a particular ignition coil "has an internal resistor". I'm not sure this is correct. I've never seen one. Maybe.
The coil winding DOES have a primary winding resistance, and it varies depending on the manufacturer and the intended application. The turns ratio between the primary and secondary windings is what determines the output voltage. It is a transformer, the ignition coil MUST be matched to whatever ignition type you're running, whether points or electronic ignition..
The dwell time is fixed with points, and the Ignitor I module. It is a compromise, because a fixed dwell isn't going to be optimal throughout the RPM range and a coil is going to run relatively hot at idle, is my understanding.
I bought an old Heathkit ignition analyzer after running into some ignition issues. Keep in mind the original OEM points design and materials that went in to distributor, cap, rotor and wiring were designed with 20,000 volt coils and a reduced primary voltage.
Now it is true that the voltage required to initiate a spark across the plug gap is only 10k or less at idle. In that sense "45,000 Volt Coil!!" is marketing hype. But it's also a factor of the input voltage into the primary winding, the turns ratio, and the spark plug gap. If you pull the ballast wire, run a .050" gap, it's going to put a lot of stress on the stock ignition components. It might seem to idle OK, but it may misfire under load or high speed and you'll see excessive voltage spikes on the firing line on the scope display.
What I found observing the ignition traces on a scope was that every piece of the ignition system has to be serviceable or stuff starts arcing to ground or crossfiring and weird stuff. Remember, they weren't designed for full time battery voltage.
If the spark plug gap is opened up - then the ignition coil output voltage will rise higher. This is generally a good thing, it means a hotter, longer, fatter spark. But if taken too far, then stuff starts burning up and misfiring and generally finding an easier path to ground.
There's one more air gap in the secondary ignition system that ALSO affects the output firing voltage and that is the air gap between the rotor tip and the distributor cap terminal. If you compare 1950s and 1960s rotors with later aftermarket or service replacements it is noticeably longer.
I had to sort through a few of them to find the right one, the part # didn't change but the part did. I think it may have been an emissions thing. These wide gap rotors seem to make the ignition coil run a fair bit hotter, because the average output is higher. That's my theory anyway. When I replaced the rotor the firing voltages settled down nicely on the scope, no more fireworks display around the engine bay.
Try to find a pre-emission era distributor rotor, and, keep the spark plug gap stock and the coil should run cooler. I've used the same Ignitor I module and a stock 30 amp generator for 20 years now. It needs a minimum of 1.5 ohms resistance in the primary circuit.
Take the time to pencil out the current flow (amperes) through the primary circuit under RUN conditions it will start to make sense why, and what, ignition coil & resistor combinations and combinations are acceptable for any given Ignition. Points type were limited to about 3 amperes. The Ignitor I will tolerate about 8 amperes. This is while the engine is running - a V8 coil has about a 66% duty cycle as it were. This is also why leaving the key on in RUN without the engine running will start roasting points & ignition coil, the current flow quickly exceeds the normal 3 to 4 amps.
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By DryLakesRacer - 4 Years Ago
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I’ve run a Pertronix ll for 6+ years using their recommended coil. Prior to installing I called their tech line (I’m about 20 miles from them) to ask about using the stock resistor. The tech said either way would be fine other than the use of the resistor would not have the same voltage to the plug. I chose to use the resistor, the engine never misfires, plugs are always clean when I check. I’ll give up a little performance for reliability any time. Good luck
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By ian57tbird - 4 Years Ago
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Just as a side point. An old friend of the family who has long since past, told me in the early days they would put a large button in the lead from the coil to the distributor to up the voltage and get a stronger spark. Possibly talking pre-war times.
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By Gene Purser - 4 Years Ago
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The gap across the button let the coil voltage rise higher. Usually trying to fire oil-fouled plugs.
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By slumlord444 - 4 Years Ago
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I've run the Pertronix I and recomended coil in my T Bird without the resistor.for many years with no issues. Switched to the Pertronix II and recomended coil with no resistor several years back and no issues. Been running the Pertronix I in my 65 Mustang with no resistor and the recomended coil for a while with no Issues. Been running a Pertronix in my Two Cylinder John Deer with no problems for many years. Maybe I'm just lucky.
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By Florida_Phil - 4 Years Ago
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I am running a Pertronix I with a Pertronix 1.5 Ohm coil with no resistor. The only problem I have had has been with the Electronic Tach. I had to add a 10 Ohm resistor to get the tach to read right. Other than that, no problems.
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By Lord Gaga - 4 Years Ago
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So, remember you old timers, the demonstration of the "Hot Spark Intensifier" at the county fair?
I'll bet the unit was nothing more than a coat button and a few wires inside that box!!!!
AH-HA!
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By BamaBob - 4 Years Ago
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I remember those demonstrations. I have a question though. How was the button installed to create the spark gap? I've tried to picture it in my mind, but it eludes me!
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By Gene Purser - 4 Years Ago
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You cut the wire and strip the insulation so there is about an inch of bare wire exposed on both pieces. Tie the stripped wire into the button holes diagonal to one another so as to create a gap for the spark to jump. I've seen them placed on an individual plug wire to help an oil fouled single plug.
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By KULTULZ - 4 Years Ago
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As a technical point, I hear people sometimes say a particular ignition coil "has an internal resistor". I'm not sure this is correct. I've never seen one. Maybe.
One Example - FORD DURASPARK I
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By BamaBob - 4 Years Ago
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Gene, thanks for the answer! My Daddy told me years ago about creating a spark gap to make Ford A-Models run, but he never told me how it was done. I remember asking him one time why it made them run better and he said he didn't know, it just did. The part about building up the voltage in the coil to create enough power to jump the gap makes perfect sense. I miss my Daddy, he's been gone 33 years now.
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By Tedster - 4 Years Ago
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I'm figuring it simply has a larger number of turns in the primary winding is what I was getting at. Can you cut that one open? Is there actually a ballast inside those coils? I don't think there is. Maybe.
Anyhoo this question about the coil ohms comes up a lot, it seems like voodoo to a lot of folks. They seem to zero in on "whether it has a resistor" or not, when what they need to do is measure it, and make sure it is compatible with the rest of the ignition.
If they would study Ohm's Law a little bit, and understand the circuit better they can use just about whatever combination of mix and match scratch and dent parts they want and it will give good service. The key is to keep the current flow within specs.
There's nothing that says one has to use Flamethrower branded coils with the Ignitors (though I'm sure Pertronix would like that) there may be better choices out there. So long as the primary/secondary resistance is the similar, it should make absolutely no difference in the performance. I replaced the oil filled unit after it started leaking after several years with an epoxy filled unit.
There are currently no domestically produced ignition coils is my understanding, but I'm told that the Bosch Blue is an excellent unit, it is a 3.0 ohm coil made in Brazil or Mexico iirc.
When I mentioned using the same Ignitor I for 20 years with excellent service, maybe Pertronix has long since offshored production for those by now. I don't know.
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By Florida_Phil - 4 Years Ago
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"There's nothing that says one has to use Flamethrower branded coils with the Ignitors (though I'm sure Pertronix would like that) there may be better choices out there." Tedster
My best friend has a 1964 Galaxy convertible. We have been running a Pertronix I module with no external resistor and an Autozone resistor coil for two years,
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By 57RancheroJim - 4 Years Ago
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But after about 1960 they stopped using an external ballast resistor and started using a resistor wire. I've has a Pertronix I in my 66 mustang using the stock resistor wire and stock coil for the past 20 years, it has worked flawlessly. My 57 I have a Pertronix II with an epoxy coil and no ballast resistor with no problems.
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By pegleg - 4 Years Ago
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Pertronix does list the requirements, in Ohms of resistance, for their distributor pickups in the instructions. Any coil that meets the !.5 Ohms of resistance (I think) should be OK
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