Can coils be adjusted to run "best" on 6 volts battery power, because a T has a bad magneto?
What I have discovered is that you can get the T coils to run so so on 6V by setting them up to a lower current than 1.3 amps but you give up spark voltage in the process. If you MUST run them on 6V just find somebody with an HCCT (Hand Cranked Coil Tester), and ask them to set them up with the usual 16 sparks around the ring but have them set up for as little as .7-.8 amps. Since the DRAIN of the entire coil box when the engine is running is about .65 amps or so, you can run for literally days on a standard 12V battery thus it is better to just get a 12V battery to run the coils off of. Even a garden tractor battery with 20 Amp-hour rating will run your T for 20/.65 or about 30 hours before that battery is totally dead. Just charge it when you get home and you can get by for a whole season until you pull the motor and fix the mag.
When I switch from Bat to Mag is is like turning on a supercharger on an aircraft engine. The engine runs smother and faster.
Ernie, my mag didn't work right after I rebuilt it (READ: "I" rebuilt it...hence the problem, it just sputtered on MAG)
I ran a 12 V Lawn & Garden tractor battery for several years. Put it under the rear seat of my touring and hooked it to the MAG wire. When I switched to "mag" I was really switching to the 12V riding mower battery. Worked fine for about 3 years.
I finally had the opportunity last spring to have the engine pulled and had the mag / transmission rebuilt.
WOW! What a difference! I was pulling hills in HIGH like I had a TURBO! I couldn't believe the difference! I commented to my wife several times how powerful our T was (self-justifying the money I spent on the rebuild) ! Yep, you can run on the 6 V battery, and even on a 12V DC battery...but there's nothing like 30 V AC Magneto power!
"Once you've gone Mag.... you'll never go back!"
To answer that from someone who has run coils off 6v for the last 6 years, the answer is indeed yes.
There's three criteria: 1) use Champion X plugs, 2)use an Anderson timer, 3)rebuild the coils and set the current to 1.7A as measured on a moving coil ammeter.
This enables me to cruise at 65km/h quite comfortably, and have got up to 75km/h on a flat road, which is quite sufficient for a Model T. This is of course without any misfiring etc.
One other thing before someone else jumps in, the contact wear is not an issue: 11000km and the points are only just pitted.
Part of the reason for the success is that the battery voltage rises to about 7V with the engine running.
I have replaced the mag in two T's in the past 9 months and have my own to do yet before summer. It isn't as bad a job as many make it out to be and you should be able to complete the task in a weekend.
The job is simplified if you have an engine stand with the proper adapter to stand the engine on its nose.
If you don't feel like doing it yourself you can probably find another T'er to do it reasonably. The last one I did I charged the guy $500 labor to pull the engine, charge the magnets and replace the feild coil, install new bands and an outside oiler, and stuff it back in the car. If it were a closed sedan I would add another $100 to it.
Post where your from as there is probably someone near you that would be willing to do it.
Like John Regan said, 12 volts would be better. So also would be throwing away the roller timer and replacing it with either an Anderson if you can afford it or a New Day if you can't. Both of these timers do a far better job of grounding the coils than a roller timer and with lower voltage, better coil grounding is a must.
Since operating at lower voltage results in delay of spark production, make sure that your spark advance linkage is free of play that robs your ability to advance the spark. With your spark lever all the way up, adjust your timing to be more like 5 degrees after instead of the Ford-recommended 15 degrees after.
Do all that and I think you'll be plenty happy with the performance.
I must respectfully disagree that setting the coils to an actual current of 1.7 amps will make them run better on 6V. Just the opposite is true. 1.7A will make the problem even worse since the higher the current setting the longer it takes for the coil to ramp up to that current before firing. I think when you have set them to 1.7A, you probably were using a BUZZ BOX type tester and the chances are good that if the coils were double sparking, you then in fact were setting them to .85A since double sparking will result in a Buzz Box tester being fooled into a reading of twice the actual spark current for each spark.
Your comment on March 3 "3-rebuild the coils and
set the current at 7.5 amps as measured on a moving coil ampmeter" I don't understand. please explain "moving"
Sticking my nose in:
On a moving coil ammeter, the coil is attached to the needle and is not a magnet rotating in a stationary coil.
And...I just remembered last night why I can't measure magneto output with my Craftsman digital multimeter. The thing goes crazy when it gets within two feet of my running engine. I'm guessing longer lead probes would only serve as antennas. I had to dig out my old analog one with the moving coil meter.
Thomas J. Miller
The T ignition coils are a source of large amounts of RFI (Radio Frequency Interference) and just about ALL digital meters give questionable readings when an operating T engine is nearby. It has little or nothing to do with the QUALITY of the digital meter. I have FLUKE labratory grade meters and small portable ones and they all jitter and give strange readings when the engine is running and the coils are sparking away. Turn on an AM radio across the room and tune it off station and listen to the tremendous amount of ignition interference static it picks up. Your digital meter is picking up the same junk.
John, I agree.
"Tom" is sufficient moniker. There is a Thomas A. Miller in the family who is also into Model Ts. There was a third, Thomas R. but he passed away last year. To add to the confusion, there are two Tom Millers here at work that own 31 Slant Window Fordors; I being one of them. Needless to say, this results in some misdirected mail.
My Craftsman meter has served me well for most jobs and I apologize to Sears if it sounded like I was doubting its quality versus some other meter such as a Fluke. The only reason I mentioned Craftsman was to differentiate it from my two dollar Harbor Freight VOMs that I keep laying around my shop in order to throw at my son when he makes clever remarks. I am very familiar with RFI and have been observed in more than one Faraday Cage.
It's just that every once in a while, I get a brainfart and forget why I keep an analog VOM in a lower cabinet drawer. At least the radio and TV in my shop are far enough away where only the flourescent lights pose a problem.
It is as though the Model T being a cheap and simple car wants only to be tested by a cheap and simple analog test meter ha ha.
Agreed, the simplest solutions (and tools) are oft times the best solutions.