Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....
That's the trouble -- correct information is almost impossible to find on the DuraSpark II.
I "lived" through the 70's troubleshooting/diagnosing the Fords -- and taught at the Ford training center sometimes.
Ford realized that dwell variation between cylinders was driving emissions higher than they could live with - caused by points - too much dwell variations, which cause timing variation and higher emissions.
They came out with the DuraSpark electronic ignition - seems like it was about '73 but not sure. It was the first version (same as Jeeps used later after they got tired of the Prestolite trash.)
Now the original is referred to as the DuraSpark I - but when there wasn't any other version, the (I) wasn't used. (You don't name your kid John the first. John gets that title AFTER John II or John III exists.)
I've seen the reference to 2 different resistor Ohm values before, but cannot verify it - never noticed. It's possible the Calif version was the lower value - IF there were two types. The lower resistance probably gave the coil a little more "poop" but would increase the current, making it even more unreliable than the higher resistance ones. It would be "pushing it."
Then later on, partly because of California, partly because of the smaller V8's - 302 etc, Ford still had an emissions problem - Ford had to do something quick.
GM had come out with their HEI in '75 - it had a much hotter spark, higher available output - about 40 KV, much longer duration time, about 2.75 ms as opposed to ALL the others of about .75 ms, and a faster rise time. And it was reliable to boot! The weak part was the rotor flashing through to ground. It was a great system!!! (Believe it or not, Pontiac built 500 cars way back in '67 with it - wasn't reliable enough, almost all were recalled. I had one till someone swiped it in one of my classes.)
Ford developed the DuraSpark II (the 2nd generation of Ford electronic ignitions) - it had to get around GM's patents, but the result was nearly identical to the GM. It was used in many California cars and the smaller V8's. It did not use an ignition resistor, had a variable dwell, a current limiter, 40 KV output, higher current, longer duration, and had similar, but different connectors than the (I)-- slightly more squared looking. The II's module looked to be identical to the (I), square aluminum box. You almost have to have them side by side to see the difference in the connectors, but they will not interchange (if they did, it would let the smoke out!)
Both I & II had a few minor problems -- one being intermittant, another being too sensitive -- it would pick up CB signals and radio interference too easy - even from mobile telephones - no cell phones then. Notice on the Dura II cars there's LOTS more ground straps to help kill the RFI - even on the lower control arms and exhaust pipes to ground the static!
And the rise time wasn't quite as fast as the GM. Fast rise time helps blow off deposits on the plugs.
The connector colors originally did signify what module was what, but so many "rebuilders" and "aftermarket" units distorted that. I think originally there was blue - Calif DuraSpark (I) that had a built in retard for starting ease - (Calif timed initial timing different and had a different advance than the 49 states.) It needed that retard to get started without bucking.
Red was the 49 state version of the DuraSpark (I) - same thing only no crank retard.
Then when the DuraSpark II came out it was black as I recall.
Then "aftermarkets" came along -- they used yellow, red, blue, black, green, pink, even clear grommets. No way to tell what you had anymore. Ford started sueing them - nearly an impossible task. Many were coming in from China.
The aftermarket folks switched tactics to dodge the lawsuits. -- they started saying "rebuilt" modules - supposedly the guts were removed, new electronics put in. They used the original aluminum boxes -- mixing up the numbers! It was a fiasco -- still is!
(I bought several (50?) blue connector modules with the California Dura I numbers on them and BLUE grommets from a defunct Ford dealer's stock -- all in Motorcraft boxes. Turns out NONE of them were Calif types with the retard circuit.
You have to go by the connectors - squared = II, rounder - (I).
As far as I know, there never was a DuraSpark III - the generation that followed the DuraSpark II was an entirely different system - TFI - Thick Film Ignition. It too had the same characteristics - output - as the GM HEI. It has a Hall effect pick-up instead of the magnetic pick-up coil. The module is mounted on the side of the distributor itself. It got rid of most of the bugs the Dura I and II had -- and had a faster rise time. (The square coil had much less iron core so the rise time got faster. It really was a great ignition, and reliable. But it still occasionally would trigger to a radio signal - tear open the stock wiring harness next to the distributor and you'll see shielded wires in the harness!
And the TFI had EST -- Electronic Spark advance -- the computer decided what the advance should be. All you could do was set initial - and that was critical to within 2 degrees.
On a scope the pattern on a Dura II, a TFI, and a GM HEI are look the same. You can't tell the difference.
The scope pattern on the DuraSpark (I) or points system look identical to each other. -- As well as most other "electronic ignitions" out there.
As far as the GM "learning" the current limiter -- that's a new one on me -- wonder if you just didn't see it or there was a connection problem - either the scope, scope's ground, or even the power wire to the coil? If there is anything that limits the +12 voltage to the coil (or he module's not grounded good - the screw through it, the current limiter shuts off, no "blip." Otherwise I don't know, I doubt it's that smart!
The EEC systems, I, II, and III were mainly fuel control, but they did have -- Electronic Spark Advance -- EST. (EEC I was a nightmare!!!!!!!!!)
The large cap and rotors on Fords were used on both the DuraSpark II and the TFI systems. The old (I) used the small caps -- as a rule -- but there were exceptions!!!
BUT-- the cap size does not always indicate I or II - I've seen the small cap distributrs used with the II -- stock original!
GO BY THE CONNECTORS OR THE SCOPE PATTERN.
The data available on websites is all over the place as far as accuracy goes.
One thing that I know for sure -- combining the best of all the ignitions makes a great system for Jeeps.
The big cap and rotor for increased insulation, with the 8MM wires.
The Ford magnetic pick-up coil inside the distributor - for simplicity.
The TFI square coil - for power.
The elimination of the ignition resistor and 10 ga wires to it - to get lots of energy to the coil.
The use of a remote heat sink mounted GM HEI module for the switching of the high power.
And -- something I haven't heard any comments on -- the use of an adjustable vacuum advance diaphram to tailer the timing advance curve to the carburetor.
Most folks when the do the ignition swap have also done a carb swap. The distributor curve has to be set properly to get the best results.
You'd never believe how much of a difference it makes to get everthing working together properly.
It's not difficult or expensive, just takes a little fiddling.
Get the ignition powerful (HEI/Ford hybrid, use the right plugs, not aftermarket trash, get the timing curve correct, and get the jetting correct.
See my previous posts on "propane trick" to get the mixture correct and see my posts on timing advance for the advance curve.
Your 258 will "come alive!!!!"
Sorry for putting everyone to sleep with the world's longest post.