Dwell reading question

[miller]

Actually dwell is the time in degrees that the points are closed.

Not questioning your experience, Ron.
Just wondering, then, why dwell has a higher range for dual points? My understanding is, that's the whole purpose of dual points, to 'lengthen' the time the points are open, making the circuit. Primary set opens the circuit, secondary closes it, making a longer 'dwell' period.
Or, am I flat wrong?

 

[miller]

Or, am I flat wrong?

Looks like I've been backwards, all these years. Live and learn!

 

[72RoadrunnerGTX]

Coil saturation occurs when the circuit is closed, the more time the points are closed, the hotter the spark when the circuit opens. With dual points, the two sets are wired in parallel and slightly staggered physically around the rotation of the cam. The circuit is closed by the first set and opened by the second set, extending the dwell angle (and coil saturation).

 

[miller]

As you, and Ron have put it, makes perfect sense to me. All my fault. Had always assumed (dangerous word), I had things figured out. Straightened my act up!
All I've ever used have been dual point, Prestolite, or Mallory.

 

[Cornpatch MO]

So, which is it? current builds in the coil while the points are open or while points are closed? Maybe I have been wrong on this all these years...................................MO

 

[72RoadrunnerGTX]

 

[toolmanmike]

Thank you pops, I tried a few different lobes and got the same results. I loosened the distributer to make sure I had it exactly at the top of the lobes. I will have to bring the point gap down to 10 to get the dwell within 30-35. You think that's what should be done? Usually I set the points at 17 and the dwell is at 30-35. But not this time. Any other suggestions will be appreciated.

Sounds like the distributor cam is worn. Dwell is the degrees the points are closed. Less point gap gets you more dwell but a small gap causes point arcing and rough running. It might be time for a mew distributor.

 

[toolmanmike]

So, which is it? current builds in the coil while the points are open or while points are closed? Maybe I have been wrong on this all these years...................................MO

Current builds in the primary coils when the points are closed. When the points open, the voltage transfers to the secondary coils and the spark occurs. Single points are limited to a little over 30 degrees of dwell. Dual points increase dwell because one set of points makes contact and the other set breaks that contact.

 

[RJRENTON]

To Ron and others....
In the Mopar/ Prestolite dual point distributor, one set of points MAKES thr coil charging circuit followed closely behind with the second set of points closing. As the distributor lobe continues to rotate, the first set of points OPENS but the coil charging circuit (primary current flow) continues to flow, increasing the magnetic energy in the coil. WHEN THE SECOND SET OF POINTS OPENS or breaks the coil's primary charging current, the high voltage spark occurs and the distributor directs this voltage to the appropriate plug via rotor cap and wires.

 

[miller]

Dang electricity! Never have gotten along with it. Believe it's the condenser, that gets re-charged, while the points are closed. It's the condenser that creates the spark, when the points break.
Know if the condenser goes bad, point contacts fry.

 

[toolmanmike]

Dang electricity! Never have gotten along with it. Believe it's the condenser, that gets re-charged, while the points are closed. It's the condenser that creates the spark, when the points break.
Know if the condenser goes bad, point contacts fry.

George.........condensers "absorb" the inductive coil magnetic field induced flow of electrons when the points OPEN. This is a normal natural coil phenomon and is actually what causes "sparkies" that make yer sparkles spark.

Without a condenser, that 0.015" points gap will burn-out. When you really OPEN a switch (and points are a special switch) there is little/NO spark strong enuff to jump a WIDE-GAPP, but that itty-bitty 0.015 points gap ain't wide enuff, so the electrons will JUMP the gap unless they are absorbed by the condenser.

NOTE: condensers are 2-metal foil conductors seperated by an insulative film. When the points close, the points actually short-out the 2-foils and DISCHARGE the condenser so there is a place ready the next time to absorb the extra electrons when the points OPEN. I went to college 4-yrs to learn that simplistic explanation.........quote from a Ignition article

 

[383man]

Coil saturation occurs when the circuit is closed, the more time the points are closed, the hotter the spark when the circuit opens. With dual points, the two sets are wired in parallel and slightly staggered physically around the rotation of the cam. The circuit is closed by the first set and opened by the second set, extending the dwell angle (and coil saturation).

Yes this is correct. The condenser does not create the spark as thats done by the coil primary winding collasping and cutting through the secondary coil windings creating a high voltage in the secondary windings that of course goes out to the dist cap and so on. The condenser sorta absorbs any spark that wants to jump across the point gap when the points open which helps the coil primary winding collaspe. And the condenser will absorb any current trying to jump the point gap as the points open and then it realeases its stored electricity once the points are open out into the primary winding helping the primary winding collasping so it collaspes faster and has a strong spark. Everyone is right as dual points are wired in parallel so they overlap each other keeping the coil primary winding grounded longer to saturate longer and build up a stronger spark. Years ago some racers would run on just one set of points until high gear and then bring in the other set to retard the timing a tad in high gear as some engines liked to retard the timing a tad in high gear for more power. I believe Bill Jenkins did this in some of his Chevys. Ron

 

[miller]

It has been educating!