Coil Mounting Query

If you change from a stock type coil to a SUPER DUTY flame thrower, the spark voltage will be very similar in voltage . A 40,000 volt flame thrower is just a rating not its output . Spark out is effected by plug gap, rotor gap, point gap , point cam design , these things effect spark voltage !
 
German guy said:
I feel a need to disagree with "Alexiskai" regarding the Model A coil environment. It is indeed a "high vibration" environment unless modified with special engine mounts. Model A engine compartments are much higher vibration areas than modern engine compartments. For a minimal price difference in an already low cost item..why save a few cents on the coil?
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I appreciate that epoxy defenders want to feel like the Model A is a special car that needs a special coil, but it really is not. You are wasting money and you're investing in a product that's not designed for your application.

If you don't believe me, maybe you'll listen to automotive professionals:
"Oil filled coils offer great heat control for street driven vehicles, while epoxy filled coils provide superior winding support for high vibration environments in off-road vehicles and boats." -- Pertronix

"In applications such as off-road, marine, or other harsh conditions, the MSD Blaster High Vibration Coil is the best choice. [Epoxy] protects the coil's internal components from high and low-frequency vibrations that are commonly experienced in racing." -- MSD Ignition

"There are serious issues with epoxy filled coils." -- Dave's Small-Body HEIs

Mainly I think people who swear by epoxy coils are mistaken in thinking that it's all upside and no downside. The downside of epoxy coils is that they are worse at heat dissipation than oil coils. This is a known fact in the automotive industry.

When choosing a coil, you have to decide whether vibration or heat is a bigger risk in your particular application. The Model A coil is not mounted on the engine, so this attitude that an epoxy coil is required because of engine vibrations is baffling. If your engine shakes so much that you consider your car the equivalent of an off-road environment... I gotta say, there might be something wrong with your engine. A well-maintained Model A is a smooth ride.

Instead, for this application, heat is clearly the biggest problem. The coil is mounted at the top of the engine bay, where it absorbs radiant heat from the engine and from the car itself if it's a hot summer day. The Model A also has dwell times well in excess of what it needs, so the coil spends a lot of time "idling," which means more heat buildup. The most important thing for coil longevity is getting rid of heat. That means oil-filled coils are the best product for this application.
 
Coils don't generally get all that hot in service since the magnet is only charged for a nano second before the points open again. What really heats them up is when a person shuts the engine off and for one reason or another, they turn the ignition back on while the points happen to be closed. If they forget to turn the ignition off or leave it on too long then the coil will overheat. It wasn't designed to be a long term electromagnet.
 
alexiskai said:
Epoxy coils are good in high vibration and high temperature environments. Sadly, the Model A is not a high vibration or temperature environment. That's why I say it has no advantages.

Epoxy is an insulator. Heat doesn't move through it quickly. While that means it can protect the coil wiring against high ambient temperatures, it also means that heat generated inside the coil stays in the coil.

In contrast, oil is a heat conductor. It rapidly moves heat away from the wiring to the coil case, where it convects away via air currents. This extends the service life of the coil's internal insulation.

There are a bunch of guys in this hobby who appear to be dedicated to the superiority of epoxy coils, but – with the exception of "correct" positioning – epoxy's benefits only apply to situations that Model A engines aren't found in, while its drawbacks apply very much to Model A situations. The bottom line for me is that I've tested dozens of vintage Model A coils, and epoxy coils are by far the type most likely to fail testing. The data don't lie.

I agree that modern coils are manufactured to low standards, but that's not a function of whether they use oil as a medium. They're just cheap. If you want a high quality coil, you can go on eBay and buy a vintage NOS Delco-Remy oil-filled coil for $40. Get a 12V external resistor coil; without a resistor, they work exactly like 6V coils. Still cheaper than a modern epoxy coil.
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I don't know what you classify as a high heat environment, but my A sees extremely high engine compartment temperatures. Vibrations are probably low, but higher than most as it's a solid mounted four cylinder with inherent vibrations. Not a high vibration environment though. High heat, and often extreme temps, even as defined by current manufacturers.

I'm not dying on the epoxy coil hill. Just had fantastic and long life from them. Four cylinder coils don't generate any heat, so that's not a concern of mine. Some of the info you reference is well after the A era and isn't applicable as they were never designed for an A, and you honestly don't see them on an A. I've never seen an MSD system on a street driven A. VW's, yeah; a common sight.

I don't really care that much. I'll take and NOS Bosch German Blue Coil over anything else out there, epoxy or oil filled. My A's run them, my VW's run them. I have more than enough as backup to outlast me.
 
Hitman said:
I'll take and NOS Bosch German Blue Coil over anything else out there, epoxy or oil filled. My A's run them, my VW's run them. I have more than enough as backup to outlast me.
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They have a street value of $200+, so if you have more than you can possibly use, consider selling them to fund your retirement.
 
I m running the FSI Flamethrower coil (with the logo painted black to make it look original) on my 30 A. I have owned several classics over the years and never had a coil fail. Is this a common problem with the A? At about $30 is it an issue?
 
I’ve been very happy with the Pertronix flamethrower epoxy-filled coil as others have mentioned. It’s mounted with wires pointing down, and I’ve had no issue with points not lasting.
 
I've running a Pertronix Flamethrower 6 V. coil for several years with no problems anywhere in my spark circuit. If money were no object, I would like to hacksaw an epoxy coil open to see if the epoxy is a solid rock or softer material adhered to the windings. If the epoxy cracks away from the windings at some point, I have no heat dissipation to speak of, results: burned up coil. If I hear sloshing around with an oil filled coil, that would mean an air space at some areas of the windings, with heat not dissipating from some windings. So... I drive around smiling and carry a spare coil under the seat.
 
mass A man said:
If I hear sloshing around with an oil filled coil, that would mean an air space at some areas of the windings, with heat not dissipating from some windings.
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A little bit of sloshing is OK. Oil expands as it heats up, so you don't want the case to be 100% full at ambient temperature. I have one of the reproduction script coils that somebody was making for a while, which are high-quality oil-filled coils, and you can definitely hear the slosh when you shake it. Still works great though.
 
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