Question for Bubba...
 

In some of your posts, you mention coil resistances, ballast resistor values and condenser values for various voltages, etc. Is there a place to find all that data? Could you spill it all here, maybe even with some explanations? Thanks!!

Re: Question for Bubba...
 

Limit the current to less then 8 amps. Put acurrent limiting circuit in series withe coil. Most modern electronic ignition have this builtin. 36fordguy

Re: Question for Bubba...
 

The factory systems have always listed the primary resistance specs but are hard to find some times . I will dig up some of these factory values and we can all discuss from there .........

Re: Question for Bubba...
 

Ok some monday morning discussion:

As this is the flathead forum lets use a 1939 Ford V8 and helmet distributor with dome coil and a dash mounted resistor. (contact points)

Both the coil and the resistor are approx .6-.7 ohms resisitance each for a total of 1.2 ohms ( cold) to 1.4 hot . Current flow will cause the resistance to increase somewhat.

The battery is 6 volts and 7.2 volts running at full charge down the road.

Using ohms law total resistance of 1.2 ohms divided into the 6 volt battery voltage would give us 5 amps of primary current.

Actually this would be the maximum current, as flow will cause the current to drop off ( 1.5 ohms hot would = 4.28 amps flow thru the circuit) .

Using these numbers i would say that the 6 volt system should never exceed 5 amps of primary current .

Change any number in this circuit and the numbers and current change......:eek:

Re: Question for Bubba...
 

To carry Bubba's comments a little further... when the engine is running, the current is 'pulsed', meaning that it is 'on', then 'off', 'on', etc. So, when we try and measure it, our 'dampened' meters give a sort of 'max-average'. And, some meters freak out, and won't give anything meaningful, at all. When I've experimented with these systems, using a varity of coils, and on 12 volts, too, I'm looking for a measured current of less than 5 amps, and also less than 4 amps. I've seen numbers in the 2.5 amp range at idle, increasing to almost 4 at higher rpm. This is all 'subjective', and includes the 'averaging', and 'damping' of my meter. (Simpson 260)
I've experimented with coils that range from a late model F-series electronic ignition coil, to a HEI coil, and several old-style-can-coils from the 50's, 60's, and 70's, and also the original flathead coils. I used readings from original flathead coils as a basis for selecting resistors to give similar readings with the other coils. At one point, with this info in hand, I mounted the F-series 'electronic' coil, somewhat permanently, and ran it on my 47 for several months. This was primarily just to prove to myself that it could work ok, and also for the 'what-the?' factor when other people saw it.
IMO, the way the points wear, and how the coil temp feels to the hand, are a couple of good indicators of good primary current.
JMO

Re: Question for Bubba...
 

So, there should be a "standard" resistance for a 6 Volt system and a different value for 12 Volt? Same with ballast resistors?
How about capacitance? Years ago, I put together an early SBC distributor with dual points on a Dyna Flyte plate. My boss gave me a big condenser to mount on the outside because there wasn't any room for one inside. Is it possible to "over condenser," or, "under condenser" a system. Wikipedia ( http://en.wikipedia.org/wiki/Ignition_system ) says that the coil and condenser form a resonant circuit. I remember taking a course dealing with resonant circuits and it didn't register very well with me. Not at all well....

Re: Question for Bubba...
 

I guess i would say "designed" rather than standard. Each vehicle is designed with desired results as far as current and voltage levels go.
These parameters are based on circuit resistance, coil inductance, rpm and overall ignition needs.
Condensors fit into this discussion as well with each coil and distributor needing different capacitance. Not enough ( low mfds) causes metal transfer on the contacts and too much ( high mfds) does the same...