did anybody who responded to my voltage question with TI actually read this link? It clearly states the TI coil has a higher ratio of secondary windings resulting in higher voltage.
http://www.tispecialty.com/articles/article4.htm

 

I did, but 69427 is correct-lier in his post above. I'm always amazed by the importance that people (and vendors) put on coil voltage. Much like male apparati, bigger is always presumed to be better.

A coil stores energy (voltage) until there is enough potential for the gap to ionize. If conditions are ideal and that only takes 2kv to accomplish, having a glossy red 40kv zoomy bling coil is irrelevant.

 

The windings ratio defines the maximum spark voltage 'potential'. The actual voltage required to jump the plug gap is a function of the gap width and a myriad of other factors related to the fuel mixture and its temperature. If the plug gap is set to the value recommended by the coil manufacturer (and the other ignition components are appropriate and in good condition), a plug will support a spark up to the maximum voltage of the coil. But, as mentioned above, it almost always takes a lot less voltage than the specified coil maximum to jump those plug gaps.

 

Higher cyl pressures will require higher voltage to jump the gap. May have been one reason for TI on the high performance gm's. That along with the high rpm and coil saturation time at those high rpms. TI was more efficient at that.

But the implementation of the hei on everything else had more to do with emissions. It had to do with both the wide plug gaps (.060) needed to fire the lean fuel mixtures they were forced to run and the need for consistency in the ignition. High gaps needed higher voltage, that's pretty straight forward. The consistency thing had to do with the fact that as soon as you start driving the point equiped car the ignition parameters start to change. The contacts burn and the rubbing block wears. So even though you were only tuning your car every 12,000 miles (that was the standard back then) at 5000 miles there was a significant change to timing from the points wear. Emissions requirements wanted a longer maintenance interval. Electronic ignition will fire exactly the same at 12,000 miles at it will at mile 1.

HEI is a good system, but it's not the holy grail of ignitions either. I worked in the field in the 70's and 80's and we had lots of gm's towed in with the lead wires broken at the pickup coil from the flexing the advance caused, dead modules, and when you had a plug wire go south instead of limping home on 7 it burned a hole through the rotor and shorted the secondary so you walked.

I run my stuff as they came. They see so few miles maintenance is really not an issue. And being a purist, I hate the sight of a big ugly old HEI cap under the hood of a non hei era car.

Steve g

Steve g

 

Okay, let's try this again. I take it you disagree with the technical accuracy of my earlier post. I don't care. I have blisters on my two typing fingers (I'm a engineer, not a typist) correcting ignition myths that keep getting propogated on this forum. I'm trying to correct your misunderstanding of how an ignition system works. It's your choice as to whether you want to learn. If so, here's Lesson #2:

A higher turns ratio DOES NOT increase the secondary voltage. The secondary voltage is, as I said before, determined by the spark plug arcover voltage. Period. Exclamation point. What a higher turns ratio does is take this plug voltage/secondary voltage and divides it down by a larger amount so that the Germanium switching transistor in the old TI boxes won't blow up. (Truth is, they still did.) The Germanium transistors in the old boxes weren't as durable or robust as the silicon transistors are in the HEI and later ignitions. Coils for points, HEI, and most other igntions have lower winding ratios because a high flyback voltage in the primary circuit isn't a big deal durability-wise.
Lesson 2.1: Coil voltage is marketing BS. Coil energy is what the ignition engineers are focused on.

 

They're OK if you do not turn many rpm's. They're crap if you peg your 7 grand tach often...spark scatter is the result.

Some folks seem to think the only alternative is to go to the HEI type distributor. But there are simple points/condensor replacement kits made that fit under a pre-HEI cap. I installed one bought from Montgomery-Ward over 35 years ago. Not a bit of trouble in 3 decades of use on multiple engines, both mouse and rat motors. And I used to shift my solid lifter 396 at 7200 rpms.

I once bought a rotten pear at the supermarket. I swore off pears ever since. Some might call that irrational behavior.

 

Hey, I'd be interested in some more details on that setup (engineering curiosity). I converted my '69 to electronic ignition in 1974 (about the same time as you were converting your distributor ). It was a Hayes setup that consisted of a reluctor wheel, pickup coil, and a remote switching box. The box lasted about 10 years before I replaced it (I wired up an HEI four terminal module in its place). Contrary to the common wives' tale repeated over and over on this forum, this box did not "suddenly die". It got progessively worse (misfire) under load. I suspect the power switching transistor was degrading/breaking down, but the box was potted up and I couldn't inspect the internals to repair it.

Love the pear story.

 

I like my points but only when coupled to a MSD or something.
this takes all the load off the points and they last much longer.

 

My OEM '69 mechanical tach dizzy. A simple reluctor wheel mounted underneath the rotor...don't mind the MSD cap-adapt in the pic...and if I remember correctly, a Hall effect sensor. It is now wired into a MSD 6A but wouldn't need to be to operate. If I had the OEM cap in place, no one could tell it didn't have points/condensor within. No external box is needed.

I don't recall the original manufacturer after all these years, but I believe Pertronix makes a similar unit available from Summit, Jeg's, etc.