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Old 07-11-2019, 12:56 PM   #21
30 Closed Cab PU
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Default Re: Flamethrower 6v coil too much power ?

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Originally Posted by M2M View Post
So if you put a larger gap in the plugs the coil will produce more volts?


Just a guess, that might be hard on the rotor/points/dist. body contacts/ and plugs, I imagine they are not designed for the increased voltage/current/power of larger gaps. Might heat them up and or decrease life of those components.

Last edited by 30 Closed Cab PU; 07-11-2019 at 01:06 PM.
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Old 07-11-2019, 04:02 PM   #22
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Default Re: Flamethrower 6v coil too much power ?

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Originally Posted by M2M View Post
So if you put a larger gap in the plugs the coil will produce more volts?
That is absolutely correct. An ignition coil is really an induction coil. The primary windings are not physically connected to the secondary windings. While points are closed, current flows through the primary windings, setting up a magnetic field. When the points open, this magnetic field collapses. This induces a current in the secondary windings. The current, however, cannot jump the plug gap immediately. It builds up voltage until the voltage is high enough to jump the plug gap. The spark occurs as soon as sufficient voltage is reached. Thus, coil voltage never rises above what is needed to jump the gap. As Mr. Brierly stated, if 20,000 volts is all that is needed, that is all the coil will produce. Actually, an oscilloscope will show an idling engine using about 5,000 volts. Snap the throttle open and you may see voltage briefly rise to 15,000 or so. That super Double Whammy "45,000 Volt Flamethrower" coil will NEVER put out close to 45,000 volts on a street engine, especially a Model A!
If you have bad plug wires, excessive plug gaps, burned off rotor or distributor cap contacts (excessive gap) you may need more of that 45,000 volt potential. Plus, a high output coil needs more amperage, which shortens point life.
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Old 07-11-2019, 04:22 PM   #23
jb-ob
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Default Re: Flamethrower 6v coil too much power ?

'New from Bratton's'....but would it hurt to try another distributor body ?


I'm told in the days of racing when their engines used old fashioned plugs, points & condensers, they always started the race with 'used' proven reliable pieces, not questionable, fresh out to the box.


I had the exact same problem you are having, number 3 spark connector shorting under the strap into the distributor body. Very close inspection revealed the smallest crack in the body, opened when hot to allow number three to short out.


Changed the distributor body & been driving ever since....
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Old 07-11-2019, 04:28 PM   #24
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Default Re: Flamethrower 6v coil too much power ?

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Originally Posted by jb-ob View Post
'New from Bratton's'....but would it hurt to try another distributor body ?


I'm told in the days of racing when their engines used old fashioned plugs, points & condensers, they always started the race with 'used' proven reliable pieces, not questionable, fresh out to the box.


I had the exact same problem you are having, number 3 spark connector shorting under the strap into the distributor body. Very close inspection revealed the smallest crack in the body, opened when hot to allow number three to short out.






Changed the distributor body & been driving ever since....





I actually think that what his problem is, cracked or carbon tracked cap.
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Old 07-11-2019, 06:27 PM   #25
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Default Re: Flamethrower 6v coil too much power ?

I had that #3/#4 cross fire once and I took too long to diagnose it. By the time I did, I could see a black dot where the spark had been tracking through the body. I was miles (I mean many hundreds of miles) from home and although I had a spare distributor, I took the easy way out. It was the end of a big day's driving and it had been "pinging most of the day. We were setting up camp when I found it. I used a drill in my fingers to make a hole in the body where it had been arcing till I could see the internal "wire" going out to #4 post. I then filled it with silicone and left it slightly "mounded" on the top of the body. Once it set (overnight), I drove on. The silicone is black and no one has noticed it yet. It was after that happened and I wanted to make sure it didn't happen on another car that I started lengthening the leads and putting the tube over #3 lead.
A bit of enginuity can keep these cars going when modern cars stop.
There's an idea for what should be an interesting thread!
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Old 07-11-2019, 08:42 PM   #26
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Default Re: Flamethrower 6v coil too much power ?

I read somewhere that a lot of black RTVs have graphite in them, so may be slightly conductive - not sure if this is true.
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Old 07-13-2019, 12:12 PM   #27
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Default Re: Flamethrower 6v coil too much power ?

If the spark plug wire-strip is contacting the distributor cap body, the spark from the number four cylinder will eventually jump through the thin insulation of the cap body and short . In most cases the spark will melt the distributor cap body under where the plug wire lays over the edge of the cap and contacts the thin insulation of the distributor cap . I have had this problem with stock replacement six volt coils . The problem isn't the FORTY thousand volt flame thrower coils that I now use on some of my model A's . The problem is TOO short plug wires or spark plugs that are too short . I use model B spark plug wires that are longer and Champion W-18 spark plugs that stand taller plugs .
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