Secret of Speed Article about distributor rotors "UPDATE"

[Joop]

.
Update:

I am told that it appeared in the following SOSS magazine
Modification to Distributor Brush issue 2 # 3 page 16

And in Ford Dealer and Service Field magazine in about 1929/30 Robert Roof
===============================================

Many years ago when they started the Secret of Speed Magazine in one of the first ones there was an article about adding pieces to the rotor electrode to have a wider area for the spark.
Can someone let me know in what number of the magazine this was printed and maybe even could scan the article that would be great. The reason for this is that we have moved and I found a rotor in a box and with a broken off side piece and like to fix it and run it but need to know what was written about it.

Thanks Joop

[Joop]

Updated my quest

[Y-Blockhead]

I don't have an answer for you but your picture got me wondering why they would do this. In order to increase the range of advance? Or increase total advance?

I have a clear cap on my distributor so I can see where the spark arcs and I can't see an advantage of this mod.

[62pan]

Can't seem to be able to post photo of article but it states to solder 3/16 piece of metal to each side of rotor.

[Synchro909]

Originally Posted by Y-Blockhead

I don't have an answer for you but your picture got me wondering why they would do this. I order to increase the range of advance? Or increase total advance?

I have a clear cap on my distributor so I can see where the spark arcs and I can't see an advantage of this mod.

From the photo in Joop's OP, I wonder if the purpose is to reduce the gap between the rotor and the contact in the body so there is less voltage lost. I can't see that the area on the rotor available for the spark would make a difference. As for advance range, these motors would have a high compression ratio and modified cam so the range needed would be reduced, not increased.
I also note that whoever modified that rotor doesn't know how to solder!

[updraught]

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Ok. So he's got 3/16 inch metal strips on each side to extend the width and curve of the metal end of the rotor button.

It says Robert Roof found that the spark was jumping entirely from one side of the distributor bush, thus stretching out the spark and causing a weaker spark. This was after a certain modified A failed to develop expected speed.

[Purdy Swoft]

Though I've got several rotors , I wouldn't waste my time .

[Y-Blockhead]

Originally Posted by Synchro909

From the photo in Joop's OP, I wonder if the purpose is to reduce the gap between the rotor and the contact in the body so there is less voltage lost. I can't see that the area on the rotor available for the spark would make a difference. As for advance range, these motors would have a high compression ratio and modified cam so the range needed would be reduced, not increased.
I also note that whoever modified that rotor doesn't know how to solder!

Purdy, I agree with everything your saying, I just could not figure any other reason to make it wider.

As for the soldering job... I can understand why that parts are no longer attached.

[40 Deluxe]

Originally Posted by Synchro909

From the photo in Joop's OP, I wonder if the purpose is to reduce the gap between the rotor and the contact in the body so there is less voltage lost.

Not correct. No voltage is lost! Actually, a wider rotor-to-contact gap will raise the voltage going to the plug. A coil only puts out enough voltage to complete a path to ground for the spark current. Typically an idling engine may take 5,000 volts to fire the plug so that is all the coil will put out. If the rotor gap is huge, it may take say, 6 or 7,000 volts to jump this gap, so that is what the coil will put out and the plug will receive that 6 or 7,000 volts. Because of compression pressure in the cylinder it normally takes more voltage to jump the plug gap than the rotor gap.
In the past I've diagnosed many a miss due to a fouled plug by holding the plug wire 1/2" or so away from each plug. When you do this to the plug that's fouled it will often start firing and RPM will go up. Holding the wire away from the plug makes the coil put out higher voltage which may force the plug to fire.

[old31]

So 40, based on what you are saying the higher the compression the engine the wider the tab on the rotor should be.

Am I correct?

I am just trying to come up with and answer as to how/why SOSS came up with there theory.

[Terry, NJ]

I think they got it wrong. Why would you do this. Closing the rotor gap is easy with out soldering. There are two ways to do this. Since you are merely moving the metal a few thousandiths, just hold the brass on the edge of a plate and tap it lightly. Or straighten out the bend in the brass a little. It doesn't take much. Be careful not to loosen the rivets. Or I suppose you just tin the brass piece. This would add a few thousandeths to the length and close the gap a little and that's all we're talking about. But how does this help? With a High Compression head, the range of advance has been shortened, so again, How does this help?
Terry

Originally Posted by Synchro909

From the photo in Joop's OP, I wonder if the purpose is to reduce the gap between the rotor and the contact in the body so there is less voltage lost. I can't see that the area on the rotor available for the spark would make a difference. As for advance range, these motors would have a high compression ratio and modified cam so the range needed would be reduced, not increased.
I also note that whoever modified that rotor doesn't know how to solder!

[jhowes]

I don't think this is as question of closing the rotor gap but is a way to change the dwell. If at high speed, the time it takes for the coil field to collapse may be longer than the time that the rotor is opposite the contact to the plug wire. For example, suppose that the rotor contact was ground down to near a point , it would fly by the distributor contacts so fast that the coil field would not have time to collapse when running at high speed. If my reasoning is correct then the wider rotor contact gives the needed time to allow the coil field to fully collapse when running at a high RPM. Jack

[Joop]

This is the article I was looking for.
Thanks Ken (62Pan) for sending it.

..

[40 Deluxe]

Originally Posted by old31

So 40, based on what you are saying the higher the compression the engine the wider the tab on the rotor should be.

Am I correct?

I am just trying to come up with and answer as to how/why SOSS came up with there theory.

No, higher compression requires higher voltage to jump the plug gap so coil output is automatically higher. Rotor gap is irrelevant. No voltage is lost when the spark jumps the rotor gap.

[40 Deluxe]

Originally Posted by jhowes

I don't think this is as question of closing the rotor gap but is a way to change the dwell. If at high speed, the time it takes for the coil field to collapse may be longer than the time that the rotor is opposite the contact to the plug wire. For example, suppose that the rotor contact was ground down to near a point , it would fly by the distributor contacts so fast that the coil field would not have time to collapse when running at high speed. If my reasoning is correct then the wider rotor contact gives the needed time to allow the coil field to fully collapse when running at a high RPM. Jack

Well, no. Dwell is determined by how long the points stay closed. What you're referring to is 'spark duration', measured in milliseconds, much, much quicker than rotor movement. Modifying the rotor tip is an exercise in futility; no useful purpose is served.

[40 Deluxe]

Originally Posted by Joop

This is the article I was looking for.
Thanks Ken (62Pan) for sending it.

..

This looks like a patch job to compensate for improper assembly of ignition components. Maybe done at a race just to get back into competition. Or perhaps to compensate for a weak coil.

[30 Closed Cab PU]

Originally Posted by Synchro909

From the photo in Joop's OP, I wonder if the purpose is to reduce the gap between the rotor and the contact in the body so there is less voltage lost. I can't see that the area on the rotor available for the spark would make a difference. As for advance range, these motors would have a high compression ratio and modified cam so the range needed would be reduced, not increased.
I also note that whoever modified that rotor doesn't know how to solder!

Could be that the rotor contact material has poor soldering characteristics,
or a larger soldering iron wattage/tip was needed. Additionally you would have to watch the amount of heat applied - could start damaging the rotor Bakelite/plastic, might also loosen the rivet holding the contact rivet.

[Synchro909]

Originally Posted by 40 Deluxe

No, higher compression requires higher voltage to jump the plug gap so coil output is automatically higher. Rotor gap is irrelevant. No voltage is lost when the spark jumps the rotor gap.

IMO, Counter intuitive, to say the least. I'm not saying you are wrong - these automobile thingies are fullof surprises.
There has been plenty of discussion here on the importance of setting that gap so it is uniform on all contacts. Why bother if it makes no difference to the voltage at the plugs? Likewise the plug gap.

[30 Closed Cab PU]

I thought one of the reasons all rotor gaps to each other should match and all Plug gaps should match each other is for best idling. If not consistent between cylinders, the amount of time for spark to occur when referenced to the points opening would vary causing even idlibng to suffer.


Please correct me if this is wrong.

[CHARLIE YAPP]

I don't know who Delux 40 is but I would listen to him (her?).
He (her) is correct. Why most people's identities hidden in this site/thing??
You want HP and stability?
There are better ways to spend your time than playing with your rotor.
Joop asked me about this. . .guess I wasn't clear enough. Was in the throughs of publishing deadlines for "Secrets" . . . 29 years and still going!! Send your questions into Secrets Magazine and let a few thousand more people from around the world take a crack at the answer. Four-Titude to you and yours.