Hot Rods Flathead Ignition Experts - Coil Adapter Question?

Need some ignition advice from the experts. My '39 convertible is struggling with what appears to be intermittent ignition issues. I'm still running the flathead (6v pos ground) with a fresh rebuilt/tuned helmet-style distributor, but I replaced the failed stock coil with the typical 2-bolt coil adapter and a Flamethrower 12v coil (no resistor - full 6v).

So here's my question, per pic below - on the adapter, the small black spring contact (#1) is made of some type of plastic-y material that, if I touch two test leads to it, will not make my multimeter signal continuity... it reads some level of resistance short of 'direct continuity'. Does this seem right? If I do the same test on the spring contact on the stock coil (#2), I read direct continuity... same as touching the two test leads to one another. So the spring contact on the stock coil is made of a different, less-insulated material than the one that came in this coil adapter... is that OK? Anybody know how these things are supposed to behave?

 

The tapered coil spring contact is for the breaker points.
The black ones are carbon, that rubs on the rotor. It's not as good a conductor as metal so won't read zero ohms.

What does the bottom of your adapter look like, for the breaker points connection?

 

Thanks! Wasn't sure if it was made of carbon or graphite or something else. It just seemed odd to me that the same test on the same contact piece on the stock coil will read zero ohms (direct continuity). Pic below shows the underside of the adapter with the carbon spring contact re-inserted into the brass barrel leading thru to the coil lead socket. It's worth noting that it's a fairly sloppy fit in there... the carbon contact piece sorta 'rattles around' in that brass sleeve, so it's really the spring that makes contact between the brass and the carbon contact piece. Again, is that how this thing should look/work/act...?

 

Yes that's how it should look. Just like the old coil, basically.
Your carbon brush does look a little loose in there, but it's probably fine.
It only moves lengthwise as the carbon wears down over thousands of miles,
and maybe a tiny bit every time the engine warms up and cools down.

Really perfect contact isn't needed anyway, because it'll just arc across there
without any trouble.

Bill

 

Father-in-law sent his original Ford coil down to Skip Haney in Florida for rebuild and eliminated all the intermittent ignition problems he was having caused poor connections in his coil adapter. He also felt it was due to the carbon brush.

 

I am wondering about the 12 volt coil being used with a 6 volt system. It might not step up the voltage enough to do a good job. The original 6 volt system does not provide 6 volts to the coil. It is reduced through a resistor to around 4 to 4.5 volts. If you upgrade your system to 12 volts, you will fry the 6 volt coil so the reverse is probably true......if you leave the 6 volt system in and use a 12 volt coil, it will reduce the voltage induced to the secondary system.

 

you can go to the pertronix web site and see the flame thrower coil listings for 6 volt systems . I have one fitted to my 46 ford starts easier, idles better. but you have to by pass resistor on ign circuit. it is a 0.6 ohm 6v coil p/n 45001

 

That's helpful - thanks! Obviously, it bothers me that this carbon brush contact behaves differently in a continuity test than the stock one does. If others have seen issues with these adapters, that tells me a lot. At this point, I'd probably adapt to a crab-style distributor if I needed to eliminate this adaptor as a variable... as opposed to going back to a stock coil. Just sucks that I've already gone so deep ($$) into running an all-new/refreshed 3-bolt helmet-style distributor setup with this adapter.

This coil is the one sold by Mac's/Speedway as intended for the coil adapter application. When I started seeing issues, I called the helpful Pertonix guys who confirmed that this coil works with 6v if you bypass the resistor or with 12v if you re-add a resistor.

 

A quick update - I just talked to the Speedway Tech Support line and explained to them how this adapter is behaving... no direct continuity between the contact brush and the coil lead pocket, or even across the contact brush itself. The tech guy didn't hesitate. He says there should be direct continuity (no resistance) when testing across those two points. They are gonna send me another coil adapter kit, and I'll return this one to them.

I'll let you guys know how the replacement unit behaves, but (anticipating that the replacement unit will behave the same way) I pushed the issue a little bit with the tech guy and he was sorta adamant that this one is faulty if I can't measure direct continuity from that carbon contact brush to the coil lead pocket. Maybe it's a known issue... bad batch from supplier...?

 

What does he mean by "direct continuity"? Very close to zero ohms?
Stuff like this has to be discussed with quantitative measurements to really get anywhere in debugging.

Resistance in the high tension side of the ignition is intentionally added to all modern engines.
Resistance wires, resistor spark plugs, some rotors have built-in resistance. Some resistance
in there, a few 1000s of ohms, is not in itself a problem.

Also small gaps in the high tension circuit (outside the combustion chamber at atmospheric pressure),
such as the gaps between the rotor and distributor cap towers, actually result in higher voltage to the
spark plugs. This is because the voltage ramps up at the coil as the magnetic field collapses
before it can jump those gaps. (also puts a higher stress on the ignition coil internal insulation.

Bill

 

Per my original post, 'direct continuity' would be the same reading as touching the two test leads together... so on a multimeter it's either a 0-ohm reading in resistance mode or the audible alert signal in continuity mode. Using continuity mode of my multimeter, touching two places on the carbon contact brush of the stock coil gives the audible alert signal... direct continuity... just like touching the test leads to one another... 0-ohms resistance. The same check on the carbon contact brush of the adapter does not audibly signal continuity... so then I switch over to resistance mode on the multimeter, and I read anywhere from 200 to 2000 ohms resistance between the carbon contact brush and the coil wire pocket as the spring-loaded brush moves around in the adapter.

THIS was my original question... should the two carbon contact brushes behave so differently when tested with a multimeter...? The brush in the stock coil reads direct continuity with 0-ohms resistance, but the one in the coil adapter is made of a material that has built-in resistance instead of direct continuity - is that by design?

Per the Speedway tech support guy, the answer is NO. When I explained the situation to him, he was immediately confident that I should read direct continuity/0-ohms/audible continuity alert by testing across the carbon contact brush to the coil wire pocket of the adapter. They are sending me a replacement, so it'll be interesting to see how it behaves.

 

As a data point I just measured the carbon brush on an original coil from a diving helmet distributor.
I pulled it out of the coil enough to get to both ends. Measures about 5 ohms if you scratch around enough to get a really clean spot.

So your question, is it by design... As I mentioned earlier, resistance in the secondary ckt is not unusual. It is by design in many modern ignitions. Is it by design in the adapter? I have no way of knowing that. But 2000 ohms by itself is not a problem. BUT, wiggling/moving it around in the adapter causing the resistance to change by a factor of 10, to me is a sign of cheap construction. Which you can see visibly in the picture you posted.

Not to further stir up the can of worms I created, what symptom(s) are you trying to solve?

 

No worm stirring at all. The car runs perfectly until it doesn't. Here's how I describe 'fail mode' - if I'm driving it, it might suddenly stumble and act as if it's not getting fuel... it'll idle roughly but will not respond to throttle, then eventually it dies. Upon restart, it may run perfectly fine, or it may still be in 'fail mode'... starts but will idle roughly, not respond to throttle, etc. It might be on the next restart, or 30 mins later, but eventually it'll fire up and run good enough to get it back home to the garage where I can usually fire it up and let it idle for anywhere from 5 to 20 mins before the cycle repeats.

Fuel is no issue. When it's in fail mode the carb squirts fine, glass bowl is full, switching between mechanical and electric pumps doesn't affect it, carb cleaner shot down the carb doesn't affect it, and the brand-new carb has been torn down, cleaned and checked twice.

When I install an inline spark checker in the coil lead, I can visibly see the spark when it's running fine and then see the spark missing when it's in fail mode and idling rough before it dies. I installed a brand-new distributor which now has only test miles on it - no change. The symptoms are the same with both the Pertronix Flamethrower II coil (45011) and an MSD coil of the same spec (8202) which is 12v, .6-ohm resistance, running straight 6v from ignition switch. Bypassing the ignition switch and dash wiring with a 6v jumper wire from the battery to the coil does not change anything when it's in that rough idle 'fail mode'. It just runs great until it doesn't... completely intermittent, and I cannot force it into fail mode.

That's where I am now... so obviously looking to at least eliminate that adapter as a variable. Any other ideas?

 

Following up... the replacement coil adapter from Speedway arrived yesterday, so I immediately hit it with the multitester. Resistance across two points on the carbon brush on this one is not zero (as Speedway tech suggested and as is the case on the stock coil), but it is a little lower - steady 150 ohms vs. 200-2000 ohms seen on the other one. I installed it and the car fired right up and idled for a good 20 mins without missing a beat. That's promising, but a proper test drive will be needed to see if it made a real difference.

 

Condensor, condensor, condensor !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

HA! Sure was hoping you'd respond here. I agree... and I replaced the condenser that came with the Dennis Carpenter-via-Speedway coil adapter, and nothing changed... behaved exactly the same. I'm now running condenser #3 that arrived with the replacement coil adapter yesterday.

It's probably worth mentioning that I've only put maybe 150 miles on this car since I bought it, and only 100 of that has been with the coil adapter and canister coil. If I'm blowing condensers in under 100 miles, surely I've got another problem... yes? The only feedback I've received which suggests an issue with my current setup questions running full 6v (no resistor) to this 12v Pertronix coil and stock points... but Pertronix says this should be fine with this coil (#45011). I thought about buying a cheap 6v coil at OReilly, wired back thru the stock resistor, just to see what happens.

 

yep,

I thought about buying a cheap 6v coil at OReilly, wired back thru the stock resistor, just to see what happens.

good choice...........try that ...........

 

It just keeps getting better. I also took this opportunity to replace the plug wires and inner terminal caps, gaskets, boots, o-rings, etc. One side's all done, but on the other side I found there's no continuity on the new Mac's inner terminal cap on #6... basically, the pocket for the #6 plug wire and the #6 terminal contact facing the rotor are not connected. Not having good luck with plastic pieces with molded-in brass electrical contacts.

 

Any update?

 

Sorry... yes. The replacement inner terminal cap arrived from Mac's Saturday, and I installed it and an internally-resisted 6v coil that afternoon (full 6v to the coil - no external resistor). So now I have all new wires, caps, coil adapter, condenser, and 6v coil on there... it fired right up and idled just fine for a good 15 mins with not even a hint of a stumble. The spark across my spark tester is now a steady blue spark where previously it was a more erratic white spark. I plan to take it out for a test drive tomorrow and can report back how that goes.... fingers crossed.

 

Is your spark tester completely inline in series, or does it have a ground lead?

 

It's just a little device placed inline at the coil or at a specific plug to allow you to see the spark (or not) to ensure that it's making fire. With the car running, you can see the spark and how it behaves... so I could see that the intermittent issues of stumbling and dying were being caused by an interruption in the spark at the coil lead.

 

Just completed a good 30-min test drive, and I think I got it licked!! She runs like a champ! Thanks for all the suggestions and input.

 

Also, for anybody interested, this is the subject of all this hoo-ha... I plan to do some cruising this week and then do the 12v conversion next week.

 

Nice!

 

I still find it hard to believe a small gap in that carbon brush causes your problem.
A normal umph ignition can easily jump 1/4" or more in free air and still make it to the spark plugs.

But I'm glad it's fixed!

Bill

 

Thanks, and I appreciate all the input. You're probably right, and I'm willing to bet that the 12v coil was the key contributor to my problem... but it's worth noting how differently the two coil adapters behaved and the fact that the Speedway flathead tech support fella was adamant that there should be no resistance measured on that coil adapter from carbon brush to coil lead pocket. It's also worth noting that Pertronix Tech twice confirmed (via phone) that using their 45011 coil in a stock 6v positive ground application is just fine as long as one bypasses the ballast resistor. Lots of conflicting guidance!! Thanks again!

 

Is there any chance it was the breaker point contact in the adapter plate that was flaky?

 

Curious why the change to 12V if everything is now good? My 36 is still 6V and with the only issue being dimmer headlights/taillights, everything else appears fine....Nice car!

 

It was always the plan to convert to 12v just for ease of maintenance, but I wasn't gonna do the conversion until the ignition issue was resolved. I'm only out the $14 cost of the 6v coil, so no harm done... everything else is 12v-ready.

Thanks!!