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02-02-2021, 08:24 PM | #1 |
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Dual points for increased dwell??
Irrelevant now
Last edited by 34fordy; 02-07-2021 at 12:21 PM. |
02-02-2021, 08:30 PM | #2 |
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Re: Dual points for increased dwell??
I'm interested in this and would like to increase my limited knowledge!!
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02-02-2021, 09:18 PM | #3 |
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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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02-02-2021, 09:54 PM | #4 |
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Re: Dual points for increased dwell??
Irrelevant now
Last edited by 34fordy; 02-07-2021 at 12:21 PM. |
02-02-2021, 10:19 PM | #5 | |
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Re: Dual points for increased dwell??
Quote:
What DID he say dual points are for? |
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02-02-2021, 10:37 PM | #6 |
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Re: Dual points for increased dwell??
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02-02-2021, 10:49 PM | #7 |
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Re: Dual points for increased dwell??
One reason for dual points is to reduce point "bounce" at high speed/rpm
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02-02-2021, 10:49 PM | #8 |
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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. |
02-03-2021, 08:08 AM | #9 |
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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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02-03-2021, 08:28 AM | #10 |
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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 |
02-03-2021, 08:30 AM | #11 |
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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. |
02-03-2021, 08:47 AM | #12 | |
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Re: Dual points for increased dwell??
Quote:
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02-03-2021, 09:45 AM | #13 |
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Re: Dual points for increased dwell??
Irrelevant now
Last edited by 34fordy; 02-07-2021 at 12:22 PM. |
02-03-2021, 10:03 AM | #14 |
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Re: Dual points for increased dwell??
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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02-03-2021, 10:13 AM | #15 |
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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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02-03-2021, 10:19 AM | #16 |
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Re: Dual points for increased dwell??
Irrelevant now
Last edited by 34fordy; 02-07-2021 at 12:22 PM. |
02-03-2021, 10:22 AM | #17 |
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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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02-03-2021, 10:38 AM | #18 |
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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. Charlie ny |
02-03-2021, 10:44 AM | #19 |
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Re: Dual points for increased dwell??
Interesting stuff. Ramble on.
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02-03-2021, 11:02 AM | #20 |
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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 |
02-03-2021, 11:19 AM | #21 | |
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Re: Dual points for increased dwell??
Quote:
1932. Plastics was in it's infancy. No nylon. The rubbing blocks were cloth/resin/thermoplastic. (Tufnol?). It might be that they were not able to do the long lever type setup because of the wear characteristics of the materials available at the time. If you had one thou wear you would have 2 at the points. Someone must have thought of that setup at some time, I wonder who was the first to adopt it. Edit: It would appear Cadillac used points like the type we have been discussing in 1932. (Maybe earlier). Mart. |
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02-03-2021, 11:26 AM | #22 |
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Re: Dual points for increased dwell??
Good thinking Mart. "Materials Science" has made a difference over the years.
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02-03-2021, 11:52 AM | #23 |
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Re: Dual points for increased dwell??
Irrelevant now
Last edited by 34fordy; 02-07-2021 at 12:23 PM. |
02-03-2021, 04:34 PM | #24 |
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Re: Dual points for increased dwell??
As previously said above, there are two types.
Remember, closed points charge the coil and open points cause the coil to throw the high voltage to the spark plugs. One way to explain it is the distributor turns 360 degrees and there are 8 times the points have to open, that leaves 45 degrees for each time the points have to open and close to fire each cylinder. In that 45 degrees, the points have to swing open and swing closed, leaving a lot less time for them to remain closed (dwell). The mechanical limitations of this action make it hard to get more than 30 degrees of dwell. One way is to have dual points that "hand-off" the dwell time so that the opening is theoretically at the 45 degree mark per cylinder with no time lost from the opening and closing action. When the first set opens, the second is still closed for a couple degrees. The other way is to build two four cylinder distributors in one, then each point set has 90 degrees of space to play in. |
02-03-2021, 05:48 PM | #25 |
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Re: Dual points for increased dwell??
I would like to offer a solution to all the problems but it would be pointless
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02-03-2021, 09:23 PM | #26 |
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Re: Dual points for increased dwell??
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02-03-2021, 09:47 PM | #27 |
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Re: Dual points for increased dwell??
How long do you figure we can dwell on this thread? Maybe if there were more points...
Sry I can't resist a punny joke. 51 MERC-CT started it |
02-03-2021, 10:02 PM | #28 |
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Re: Dual points for increased dwell??
Anybody remember the Sanchez Cagle Stude ?...2 flatheads. Belmont Sanchez owned a Stude dealership in Cal and built the car with Blackie's motors in '53....it was a brand new Stude........nobody ?
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02-03-2021, 10:18 PM | #29 | |
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Re: Dual points for increased dwell??
Quote:
Any pics by chance? |
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02-04-2021, 08:10 AM | #30 | |
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Re: Dual points for increased dwell??
Quote:
https://www.hotrod.com/articles/1953-studebaker-coupe/
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02-04-2021, 01:43 PM | #31 | |
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Re: Dual points for increased dwell??
Quote:
Sounds like the engines were Chrysler Hemis, not flatheads. |
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02-04-2021, 01:54 PM | #32 |
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Re: Dual points for increased dwell??
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02-04-2021, 03:07 PM | #33 |
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Re: Dual points for increased dwell??
At least for a part of the time that the coil has current flowing through it, both points are closed. During that time both would have to "bounce" open in order to break the circuit. During the time both sets are closed, I guess you could say the chance of point bounce is cut in half, not doubled.
First, one point closes which allows current to flow. Then the other one closes which does nothing. Then the first point opens, which does nothing because the second set is closed. Then the second set opens which stops the current and as the magnetic field collapses in the coil, a large voltage spike is created for a short time. |
02-04-2021, 03:53 PM | #34 | |
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Re: Dual points for increased dwell??
Quote:
That makes since that I did not think of in terms of the point bounce. Although there is only 10 degrees of overlap so it only helps for 28.5 percent of the cycle. |
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02-04-2021, 04:09 PM | #35 |
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Re: Dual points for increased dwell??
But if the dwell is somewhere around 30 degrees, then the overlap is most of the time.
I think that's right anyway. I'm too old to think hard anyway. It's snowing real bad here in Wisconsin, I'd rather be in Tenn. |
02-04-2021, 06:47 PM | #36 |
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Re: Dual points for increased dwell??
Some of the hot rodders back in the day were also using dual coil set ups which required either dual caps or one cap on top of the other so that the high tension could be delivered. These used two sets of points and two condensers as well as the dual coils.
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02-04-2021, 07:15 PM | #37 | |
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Re: Dual points for increased dwell??
Quote:
There have been a couple threads on the H.A.M.B. about these. It seems that over the last 50 or 60 years, the coils and distributors have become separated and people can't figure out how they work. I once had a 1948 Seagrave fire engine that had the Pierce-Arrow derived V12 engine. The engine had dual ignition and had 24 spark plugs (H10's BTW), two distributors and 4 coils. It was impressive looking, that's for sure. |
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02-04-2021, 07:56 PM | #38 | |
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Re: Dual points for increased dwell??
Quote:
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02-07-2021, 10:23 AM | #39 | |
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Re: Dual points for increased dwell??
Quote:
https://youtu.be/x5qkNlsskCo
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02-07-2021, 11:38 AM | #40 |
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Re: Dual points for increased dwell??
The actual Lycoming BB V12 engines are pretty rare since Auburn only made 14 speedsters with that engine. They only had single spark plug ignition for those. When American LaFrance purchased the rights to the engine and tooling, it was changed to dual spark plug ignition so this is how a person can tell one from the other aside from the engine data plate and various casting markings.
The Seagrave engines were made from a Pierce Arrow design V12. Those old fire trucks were big and heavy so they needed a powerful engine and a lot of gearing to get them going in a hurry. Lincoln V12 distributors were modified to work for flat V8s as well. |
02-07-2021, 02:03 PM | #41 |
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Re: Dual points for increased dwell??
I'll bet ya that if someone asks really nicely, the "tubman" will be happy to reiterate the story about the brakes that WOULDN'T get them Seagraves "stopped in a hurry". DD
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02-07-2021, 06:44 PM | #42 |
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Re: Dual points for increased dwell??
My Seagrave had power brakes that usually worked fine, thank you. However, the gas gauge wasn't very consistent and I ran out of gas going to The Burnsville (MN) Fire Muster one beautiful Saturday morning. It was like there were no brakes at all. I was literally standing on the brake pedal with both feet pulling up as hard as I could on the steering wheel before they became even the least little bit effective. I was able to pull into an empty parking lot and got it stopped. I put some gas in it, got it started and the brakes were as effective as ever. It was one scary experience, and I kept the gas tank full from then on.
This was a nice original truck with 2300 road miles and 17,000 engine (pumping) miles. It could easily exceed 70 MPH on a straight level road. |
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02-07-2021, 07:13 PM | #43 | |
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Re: Dual points for increased dwell??
Quote:
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