point gap or dwell degrees

[Thomas]

Originally Posted by BioTex

... I just spent over an hour reading up on anything i could find on how to set dwell on an electronic ignition. I could not find anything that said the air gap sets dwell...

---IIRC it is near the first two paragraphs of the introduction to the Ignition systems. Sorry I can't help you more than that but my manuals are a few towns over.

[Greg R]

dwell on an electronic ignition.

As many have suspected, it (DWELL) is electronically controlled or set. Whether it's in the ECM, or the trigger module in the distributor, it's pretty much locked in an eprom or micro controller. Some of the real early Hall Effect triggers used shutter wheels were the widths of the shutter/windows determined dwell.

There are some folks out there who have claimed to have modified it adjusting the air gap. But if you really read the crap, they adjusted the gap to the point of almost damaging the unit, yes distance and field strength would change a value, and only got maybe a degree or so of change. Not worth it in my book and another beerthirty b.s. legend bites the dust.

The new Pertronix 2 is advertising adaptable dwell, so again the dwell is electronically set. I don't know of any other way, other than computer controllers, you would even want to.

The whole purpose of Dwell was to accurately time mechanically the plug firing with piston position. Point gap got you there roughly, dwell got you there precisely. In a perfect world, (before electronics), it was to be a fixed value that never changed. You only checked it to compensate for point wear. Well now with electronic triggers, it is a value that doesn't change, unless electronically engineered to do so, so why f**k with it.

[Eric VanBuren]

On a flying magnet system like the Pertronix yes the "dwell" is adjustable by changing the gap.

On a Variable Reluctance pickup like used in the Duraspark or Mopar pickup conversion and the GM HEI systems adjusting the gap will not change the dwell.

On the Mopar system when you set the air gap (it is not adjustable on the Duraspark or HEI) you should use a non-magnetic feeler gauge, not because you can damage things but because there are magnets present you won't get an accurate "feel".

On a true Hall effect (non flying magnet) system you can not change the dwell, that sometimes is determined by the size of the shutter wheel, sometimes not.

However IH never used any of those systems in the Light line electronic ignitions systems. The Prestolite ignition system whether marketed as a Prestolite or Holley gold box use a pulse inductance system. It's dwell will not be changed by adjusting the air gap and since there are no magnets present you can measure it's gap with a plain old STEEL feeler gauge. (check the IH FSM there is absolutly no mention of using a non magnetic feeler gauge) It won't hurt anything and since there are no magnets present you can get an accurate "feel".

[Greg R]

Well Eric, I will agree to disagree.

Unless I'm missing something, all my sources show that dwell is electronic when it's electronic trigger or the whole shebang. Be they Automotive Engines educational course books, (with Chry, Ford, GM sources) or after market electronic ignition books with contributions from Crane, Mallory, Jacobs, etc.

I'm not saying it can't be done because one is physically manipulating parameters outside of those specified.

What I am saying is it doesn't make it right; and those who may not know the difference can be lead into thinking that's how it's done when it ain't supposed to.

[BioTex]

I don't have any IH manuals that cover EI, so that is why I'm at a disadvantage. IH borrowed the technology from others anyway, so I guess the internet is as good a source as any.




Oh, and thank you all for muddying up the unclear waters...

[Eric VanBuren]

Originally Posted by Greg R

Well Eric, I will agree to disagree.

Unless I'm missing something, all my sources show that dwell is electronic when it's electronic trigger or the whole shebang. Be they Automotive Engines educational course books, (with Chry, Ford, GM sources) or after market electronic ignition books with contributions from Crane, Mallory, Jacobs, etc.

I'm not saying it can't be done because one is physically manipulating parameters outside of those specified.

What I am saying is it doesn't make it right; and those who may not know the difference can be lead into thinking that's how it's done when it ain't supposed to.

Greg, What are we agreeing to disagree on?

I think we do agree that on most electronic systems "Dwell" is not adjustable.

The only exception is the Pertronix I. The Pertronix I is the oldest most primitive electronic ignition system you can still purchase new. As such it acts much like points with its flying magnet system where the dwell is a "set" by the proximity of N and S poles of the magnet. As one pole gets close to the trigger it starts charging the coil and as the other pole gets close to the trigger it breaks the circuit and triggers the coil to fire. So yes you can adjust the "dwell" on a Pertronix I by adjusting the air gap, on those Pertronix I that are equipped with an adjustable mounting.

[Jay Tabor]

i seem to recall a magnetic pull to the steel feeler gauges I used on the Holly pick up.
didnt feel it when using brass gauges.

[Eric VanBuren]

Originally Posted by Jay Tabor

i seem to recall a magnetic pull to the steel feeler gauges I used on the Holly pick up.
didnt feel it when using brass gauges.

You must have imagined it or are having a selective memory as the Prestolite pulse inductance pickup does not have a magnet in it. Yes the Prestolite pickup is what was used in the Holley system as it was made for Holley by Prestolite. Prestolite earned Holley's supplier of the year award for supplying them with their electronic ignition system.

[Thomas]

Originally Posted by BioTex

... IH borrowed the technology from others anyway...

---If that were the case, then I guess you'd be able to find it anywhere. They have had their own designs long before most even thought of cars.

---As for the muddy waters, they're not cleared until second guessing stops and someone quotes the manuals. Guess opening a book is beneath most. I commend you on your quest for knowledge, just don't let it be short-lived cause when it's stumbled on at a later date, I doubt many will come back and say, "Hey, guess what...".

[Greg R]

I emailed Pertronix, and I got a totally unexpected answer: