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Old 02-02-2021, 08:24 PM   #1
34fordy
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Default Dual points for increased dwell??

Irrelevant now

Last edited by 34fordy; 02-07-2021 at 12:21 PM.
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Old 02-02-2021, 08:30 PM   #2
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Default Re: Dual points for increased dwell??

I'm interested in this and would like to increase my limited knowledge!!
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Old 02-02-2021, 09:18 PM   #3
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Default Re: Dual points for increased dwell??

I'm not familiar with the guru you cited as having knowledge contrary to what has always been common knowledge about Ford's dual points, so I'll leave that conversation to others. What i will do is to paint a word picture of the system as I understand it, hopefully sufficient for others also:
The cam lobes within the distributor opens and closes two separate followers, one after the other. The first follower makes the circuit as it drops off a lobe, and while that follower quickly rides up on the next lobe, the second follower has already dropped off an opposing lobe, which continues the contact for a moment longer. This slightly longer maintenance of the magnetic circuit within the coil increases the available spark which occurs when the second follower rides up the next lobe, breaking the circuit, and delivering the spark to the rotor.

Now, in second guessing my own answer, I may have it backwards as to which makes and breaks the circuit, but either way, the effect of two sets of points is that it allows a longer period of time to build the spark than a single set of points could provide.
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Old 02-02-2021, 09:54 PM   #4
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Default Re: Dual points for increased dwell??

Irrelevant now

Last edited by 34fordy; 02-07-2021 at 12:21 PM.
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Old 02-02-2021, 10:19 PM   #5
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Default Re: Dual points for increased dwell??

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Originally Posted by 34fordy View Post
I did some searching and found an article on the internet written by MAGguru.com explaining the Mallory dual point distributor. He explained that the dual points had little or nothing to do with wanting increased dwell time. I will say up front that what he explained made real sense to me.
Googling magguru.com brings up a domain for sale site.

What DID he say dual points are for?
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Old 02-02-2021, 10:37 PM   #6
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Default Re: Dual points for increased dwell??

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I found (I think) the article you read. Notice he is a MGA (British sport car) expert comparing 4 cylinder distributors that already have 60 degrees of dwell (he says). Naturally, dwell isn't a concern to him so he focuses on stability and reliability for the MGA over the Lucas distributor. From what I read about Lucas electrical systems, most anything is better.

http://mgaguru.com/mgtech/ignition/ig200.htm
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Old 02-02-2021, 10:49 PM   #7
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Default Re: Dual points for increased dwell??

One reason for dual points is to reduce point "bounce" at high speed/rpm
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Old 02-02-2021, 10:49 PM   #8
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Default Re: Dual points for increased dwell??

Given the technology of coils in the 1930's and the Distributor cam design, dual points were indeed necessary on 32-48 stock Fords. original Ford coils need a minimum of 30-32 degrees of dwell to charge properly. The Most dwell that can safely be accomplished with one single point on a 32-48 is 30 degrees. That is with .006" breaker gap which would cause issues. Try driving one with less than 30 degrees or .006 gap and you'll see why dual points were needed. Now...... With a different cam or point pivot design it it is possible to get the needed 35-36 degrees.. I have done it using 1964?? Ford points and re-driling the breaker plate (1937-41). Simply stated Ford did indeed do it for increased dwell time, and as years passed they found a way to redesign the cam and entire point design to allow for one set of points.

As for the later 1950's Mallory Dual Point distributors I think is it all hogwash and a marketing scheme as with two sets of points only one set actually releases the charge from the coil.

Just my opinion of the evolution of technology.

Point Bounce is related to the point spring tension and one or two points would not affect that.
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Old 02-03-2021, 08:08 AM   #9
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Default Re: Dual points for increased dwell??

As I understand it, you get spark when both sets open. The coil is charging when either set is closed. It reduces the time it takes for the points to close. Once the burn is established spark is not needed.

Michael gave a great explanation. I do know Ford was putting dual point distributors in their 289 hipo engines and I assume it was for high revs. They even ran a larger alternator pulley to not burn it out. But like Michael said, it was probably more of a gimmick than something that was actually needed.
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Old 02-03-2021, 08:28 AM   #10
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Default Re: Dual points for increased dwell??

For 8 cylinders there's 8lobe cam dual points where one set closes the circuit, other open
Another way Is 4 lobe cam for 8 cylinders ,each set of points operating 4 cylinders alternately
Both are ways to more dwell
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Old 02-03-2021, 08:30 AM   #11
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Default Re: Dual points for increased dwell??

Michael (35fordtn) summed it up and his description fits in with my understanding.

1932 technology.

You need 30+ degrees dwell to charge the coil. To do that with the single points of the day the points gap would be too small.

Dual points allow 30 degrees + but allow each pair of points to open to an acceptable gap.

If you look at th early ford points, they are more or less a bellcrank where the lift at the heel is not significantly mulitplied into much extra movement at the points.

Many modern designs use the points rubbing heel located half way along a long lever with the points at the tip. so you get (I'm guessing) twice as much points gap generated relative to cam lift.

That is (in my mind at least) how they can use a single set of points in a V8 application and generate both a decent dwell angle and an adequate points gap.

Mart.
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Old 02-03-2021, 08:47 AM   #12
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Default Re: Dual points for increased dwell??

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Originally Posted by Mart View Post
Michael (35fordtn) summed it up and his description fits in with my understanding.

1932 technology.

You need 30+ degrees dwell to charge the coil. To do that with the single points of the day the points gap would be too small.

Dual points allow 30 degrees + but allow each pair of points to open to an acceptable gap.

If you look at th early ford points, they are more or less a bellcrank where the lift at the heel is not significantly mulitplied into much extra movement at the points.

Many modern designs use the points rubbing heel located half way along a long lever with the points at the tip. so you get (I'm guessing) twice as much points gap generated relative to cam lift.

That is (in my mind at least) how they can use a single set of points in a V8 application and generate both a decent dwell angle and an adequate points gap.

Mart.
Exactly Mart. If Ford had thought of the more modern design with the rubbing block closer to the pivot point single points would have been all that was needed on the V-8's.
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Old 02-03-2021, 09:45 AM   #13
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Default Re: Dual points for increased dwell??

Irrelevant now

Last edited by 34fordy; 02-07-2021 at 12:22 PM.
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Old 02-03-2021, 10:03 AM   #14
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Default Re: Dual points for increased dwell??

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Now this is interesting. How could the Ford engineers have missed such a simple principle like that?
That I sure couldn’t tell ya. The dual point design does work quite well on these distributors and was certainly thought out well by engineers, so I can agree I don’t understand the reasoning they didn’t go ahead and design a cam and set of points to use a single point set up. A old Ford guru once told me it was because if one set burned up the other set would get you to a garage. I find that not to be true as the timing would be WAY off and the old coils wouldn’t fire a plug at 22.5 degrees of dwell.
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Old 02-03-2021, 10:13 AM   #15
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Default Re: Dual points for increased dwell??

I think what your trying to say is you’ll have a longer spark !,cleaner and more efficient fuel burn !
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Old 02-03-2021, 10:19 AM   #16
34fordy
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Default Re: Dual points for increased dwell??

Irrelevant now

Last edited by 34fordy; 02-07-2021 at 12:22 PM.
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Old 02-03-2021, 10:22 AM   #17
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Default Re: Dual points for increased dwell??

I was under the impression (and I can't remember where I got that impression) that one set of points does the closeing and then the other set does the opening and that the corresponding wear is different on both sets. This was intended for the points to last way longer. Please correct me if I'm way off base here. Thanks!
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Old 02-03-2021, 10:38 AM   #18
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Default Re: Dual points for increased dwell??

Anybody here remember Blackie Gold from Utah or Texas. When we conversed over
the ph or snail mail it was always re: flatheads. This topic came up at some point and
Blackie's take was that Henry was so happy with Emil Zoerlin's distributor design that he
he told Sorenson ( cast iron Charlie ) to concentrate on core shift and poor oil mileage.
Blackie claimed he taught Barney Navarro everything Barney knew and further more,
he, Blackie, built more full race flatheads than anyone he knew of at the time.
Mr. Gold was a dry lakes guy and never missed an event...I guess at B'ville.
I still have one of his letters to me describing building the 2 flatheads for the Sanchez Cagle '53 Studebaker B'ville car.
I'm 80 let me ramble.
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Old 02-03-2021, 10:44 AM   #19
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Default Re: Dual points for increased dwell??

Interesting stuff. Ramble on.
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Old 02-03-2021, 11:02 AM   #20
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Default Re: Dual points for increased dwell??

Here's tons more info. on advantages of dual points.
https://www.google.com/search?q=adva...hrome&ie=UTF-8
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