Hyper_pak
Old School Chrysler Fan
I was going to mention the Mallory Double Life and Dual Point subject, but it looks like you guys caught that while I was asleep last night.
Slant 6 Dual Point Distributor Conversion.
- Thread starter RustyRatRod
- Start date
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Rob they both have to be open at some time to build up the dwell time. Good example is a stock DP. Both set at 30 degree dwell and when they are read combined usually about 42 dwell. If one closes completely it stops the added dwell and would read 30 ish. Hope that made sense.
Stole this
With two contact sets mechanically offset by 9 degrees, the closed period for the two sets overlaps by 23 degrees but extends the total dwell angle from 32 degrees to 41 degrees. ... When the 8-cylinder Mallory Dual Points makes 33 degrees dwell it is down to only 12 degrees open. You might see where this trend is going.
The points act at nearly but not exactly the same time. There is overlap or a "handoff", meaning that the contact made between the power supply and the coil stays longer, leading to a higher saturation or "charge" in the coil, leading to a higher voltage spark. (by the way, there's no such thing as a "longer" spark, if "longer" means time, but a higher voltage spark can travel a longer distance over a bigger gap).
Think of it like this, you have Points A and Points B, as the cam turns, Points A reach the low spot first (they Close) and get charged while on the low spot. B follows and continues the circuit. Turn more and Points A reach the high spot and open, but B isn't there yet so the circuit is still closed. When B reaches the high spot the circuit is opened and the coil fires.
Stole this
With two contact sets mechanically offset by 9 degrees, the closed period for the two sets overlaps by 23 degrees but extends the total dwell angle from 32 degrees to 41 degrees. ... When the 8-cylinder Mallory Dual Points makes 33 degrees dwell it is down to only 12 degrees open. You might see where this trend is going.
The points act at nearly but not exactly the same time. There is overlap or a "handoff", meaning that the contact made between the power supply and the coil stays longer, leading to a higher saturation or "charge" in the coil, leading to a higher voltage spark. (by the way, there's no such thing as a "longer" spark, if "longer" means time, but a higher voltage spark can travel a longer distance over a bigger gap).
Think of it like this, you have Points A and Points B, as the cam turns, Points A reach the low spot first (they Close) and get charged while on the low spot. B follows and continues the circuit. Turn more and Points A reach the high spot and open, but B isn't there yet so the circuit is still closed. When B reaches the high spot the circuit is opened and the coil fires.
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67Dart273
Well-Known Member
Easy, rob. Set the points put an ohmeter/ continuity check on it and see if it makes and breaks. You can rig a drill, etc to check dwell out of the car, might even do so spinning it by hand You can also check rotor phasing. Open up an old cap so you can see one or two towers and then with a continuity checker on the points, slowly and carefully turn dist so points break. You should be able to easily see rotor relationship. I would pump down vacuum can, if you are using it, to make sure rotor stays within "range" as the vacuum moves it's range.
By the way I have a new in box "dual" electronic distributor like used on the late 70's, what you called it!!? You know,the electronic setup that was prone to fail!!! (New and cheap $30). Or trade for donuts. Would such have any application for you distributor hot rodders??
Lean burn. Only trouble is, they don't have a mechanical advance mechanism. I would be willing to bet you could Frankenstein one in it.
Yeah, I thought about the meter after I went to bed this mornin. I'll break that out in a little bit.
I don't think there's really any way to make this work without moving something. Both points are only open for a very, very short time, so I don't see how the coil could get saturated. I'm sure they're open less than 10 degrees. Maybe less than 5.
Yes Lean Burn!!!! I had a brain fart!
Anyway, something for a hotrodder to think on!? lol
Being only 6 lobes I'd think you could get more dwell time out of each set of points vs a V8.
My question would be with equal centrifugal and vacuum advance what would you gain vs a good electronic ignition setup? Especially in an A body you'd have 2x the PITA setting up a points distributor, not a real abundance of space down there anyway on that side of the engine to fart with 1 set of points let alone 2 sets.
My question would be with equal centrifugal and vacuum advance what would you gain vs a good electronic ignition setup? Especially in an A body you'd have 2x the PITA setting up a points distributor, not a real abundance of space down there anyway on that side of the engine to fart with 1 set of points let alone 2 sets.
Well, it's more about the era I am aiming my car to be built towards. A dual point fits that agenda. I ain't skeered of points. IF I can get it to work, I will. I might move one of the point sets locating pins. I just need to figure out "where". Then again, I may just leave it single points. "Whatever" I do, the points stay. lol
Halifax has the right idea. One byproduct of the Prestolite dual point design is that if one point set fails completely, it still runs with reduced dwell. In fact, that's how you are supposed to check the individual dwell – by blocking one set open with an insulating block (like a wooden matchstick) and reading the dwell running on the other set.
67Dart273
Well-Known Member
It's the other way around. "Dwell time" is points closed time and that is when the coil saturates---with DC current. But it DOES have to be open long enough for the spark to happen. And open is when the spark happens Only way I'd know how to do that would be to put it on a scope with a working coil and "simulated" plug gaps and see what it looks like. Actually you likely only need one gap........just run the coil wire to a plug and "scope" that. You'd want to check it at simulated idle, and expected max RPM, bearing in mind that's half crank RPM so spinning the dist. 3K is likely all you need
Need something turns that fast? How about an angle head buffer or grinder?
In that case, I'm sure they are open long enough. I haven't put the meter on it yet, but I will shortly. Thanks, Del
That's a little harder to do. The slant distributor has a gear on the bottom of it. I can turn it by hand though.
Both sets are making according to the meter and breaking for a short time according to the meter.
What offset degree did you figure you needed?
Crapped if I know. LOL
67Dart273
Well-Known Member
By the way you don't have to have an igntion scope to see, if you have or know someone has "just about any" oscilloscope, you can wrap a few turns of insulated wire around the coil wire and observe the pattern. Trigger it off the points just like a tach
Bear in mind you need a "good condenser" to make it work right
Bear in mind you need a "good condenser" to make it work right
Act like I'm stupid....."WHAT" am I lookin for?
67Dart273
Well-Known Member
Sorry........any sort of oscilloscope.......ignition scope, electronics bench scope, it does not have to be "much a one." Any electronics hobbyiest/ ham operators in your 'hood?
What this will do is allow you to see if the "open" time is enough to capture the energy that "should be" in the spark
Here's a quickie I searched off the internet
Notice that the plug fires showing as a horizontal line. The plug is "pulling down" the voltage because of conditions in the cylinder. Then they show "coil oscillations." These are the last of the dying energy of the coil AFTER the plug has pulled down and loaded down the coil so much that it just won't "jump" anymore, and not the coil is "petering out. FROM THAT POINT to "points closed" which in this is labled "control module again allows primary current to flow" that is the same as "points closing."
WHAT YOU WOULD WANT is to make certain that there is "some space" in that area as shown in this example........in other words if the points do not stay open long enough, they might close again BEFORE the plug has stopped firing----thus robbing the firing cylinder of possible spark energy. The point to the far right is at the same time as the point at the left whichs says "secondary voltage building." That is the point at "points open"
OK I managed to red-neck doctor the image a bit
Supposted to be a (1)........Points open The large spike is the immediate spark voltage climbing to the roof. At some point the plug gap ionizes, pulling (dragging) the firing voltage down to the "spark line"
(2) Conditions in the cylinder and the coil / capacitor deteriorating energy the plug stops firing. The tiny upswing at the end is the voltage trying to climb, but there just is no more energy. Now the coil oscillations are the coil and capacitor trading energy back and forth, known as "ringing" (like a bell). Points are still open
3....Points re-close, coil starts drawing current and building a magnetic field
(1) Back to points open and we do it all again
What this will do is allow you to see if the "open" time is enough to capture the energy that "should be" in the spark
Here's a quickie I searched off the internet
Notice that the plug fires showing as a horizontal line. The plug is "pulling down" the voltage because of conditions in the cylinder. Then they show "coil oscillations." These are the last of the dying energy of the coil AFTER the plug has pulled down and loaded down the coil so much that it just won't "jump" anymore, and not the coil is "petering out. FROM THAT POINT to "points closed" which in this is labled "control module again allows primary current to flow" that is the same as "points closing."
WHAT YOU WOULD WANT is to make certain that there is "some space" in that area as shown in this example........in other words if the points do not stay open long enough, they might close again BEFORE the plug has stopped firing----thus robbing the firing cylinder of possible spark energy. The point to the far right is at the same time as the point at the left whichs says "secondary voltage building." That is the point at "points open"
OK I managed to red-neck doctor the image a bit
Supposted to be a (1)........Points open The large spike is the immediate spark voltage climbing to the roof. At some point the plug gap ionizes, pulling (dragging) the firing voltage down to the "spark line"
(2) Conditions in the cylinder and the coil / capacitor deteriorating energy the plug stops firing. The tiny upswing at the end is the voltage trying to climb, but there just is no more energy. Now the coil oscillations are the coil and capacitor trading energy back and forth, known as "ringing" (like a bell). Points are still open
3....Points re-close, coil starts drawing current and building a magnetic field
(1) Back to points open and we do it all again
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Yeah, I've seen that before, forever ago in auto shop when out instructor was trying to show us how to use the scope. Needless to say "it didn't stick". LOL
Thanks, Del. It's kinda makin sense now.
pishta
I know I'm right....
I say run the one set of points under that wiz bang cap with the funny connectors and mums the word on how it works. 6 lobe distributor has more than enough time to saturate the coil between events..or just run an adapted Vertex 6. Set you back more than your motors machine work alone.
If I run single points, the one that's in it ain't comin out. It's doin fine. lol
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