single and dual points

Posted By: moparrookie

single and dual points - 09/07/10 10:26 PM

with a 440 what would be the advantage to dual points? would they be set to open and close at the same time? would it take a special dist or cap?

Just wondering what the advantage would be.

Posted By: Commando1

Re: single and dual points - 09/07/10 10:34 PM

It takes a special distributor.

Dual points are from an era where mechanical electrical systems (i.e. single point distributers) couldn't keep up with the engine's needs
Today, with with the electonic systems available, it's an obsolete idea.
The only reason to go dual points is extra performance and that extra performance won't even come close to what you'd get from an all electronic high performance system.
It would make for a nice nostalgia piece but who cares what it looks like under the distributer cap.
Don't give dual points a moments extra consideration these days.

Posted By: Ply72rr

Re: single and dual points - 09/07/10 10:39 PM

The duel points are set up so they open and close at slightly different time.I think this allows the coil to store a bit more energy due to the longer dwell time.

Posted By: scratchnfotraction

Re: single and dual points - 09/07/10 10:40 PM

I got a duel point dizzy for a 440

old mallory,it has 4 cam lobes on the shaft

one set works 4 cyls and the other set work the other 4 cyls

but they do have them with 8 lobes also

it gives a much hotter spark with duel points is the reason..from what i under stand

what kinda duel point do you have?

mine has a 2 piece cap that holds the wires to the cap inside on the electrode pins

had solid core wires on it also

also its a mech advance not a vac advance

would have a performance advance curve

its all greek to me but will be useing it soon,may throw a pertronix points conversion in it to ease the pain of setting both sets of points but keep the performance mech adv curve

Posted By: moparrookie

Re: single and dual points - 09/07/10 11:58 PM

I have electronic but was curious about the dual points. I had no idea how it worked an why. Thanks for a great explanation guys.

Posted By: scratchnfotraction

Re: single and dual points - 09/08/10 02:34 AM

heres a pic of mine

thats the condencer for both sets of points on the outside

I am into the old stuff myself,upgrade it to pertronix for the duel points and let it rip

I run a points dizzy in all of mine,with and with out the conversion

but i am not trying to squeeze every last drop of performance out of my junk either

on the 440 truck it will be the nostalga look i am after any ways

the solid core non surpression wires will cause havok with the radio

the look at other peoples face at a stop light is priceless

I rev mine up..their radio screams

buzzed a few of the super dooper bumper radio systems just to wtch them

want a pic under the cap showing the 4 cam lobes and duel points?

Attached picture 6183574-duelpointsdist.jpg

Posted By: RapidRobert

Re: single and dual points - 09/08/10 01:32 PM

Quote:

heres a pic of mine

Lookes like one I (my buddy actually) used to have

Posted By: Cudajon

Re: single and dual points - 09/08/10 01:51 PM

Ran one of those mallory's on a Hemi for years loved it.....It's called dwell. the longer the points stayed closed the longer voltage was supplied to the coil building up more energy. Dual points increased the dwell and was the hot setup back in the days. The mallory because it had four lopes and two sets of points allowed each set to remain closed longer. The deal about the mallory was it was stable to 4000 rpm (8000 engine rpm) Put some of these old distributors on a test machine and usually around 2 - 3000 rpm they would get into spark scatter and all kinds of bad stuff. Thats why MSD, Accel, and Mallory had such a good business, stock dizzys couldn't cut it. All stock dizzys have the problem even electronic ones. Thats why it pays to run a "good" aftermarket dizzy.

Posted By: scratchnfotraction

Re: single and dual points - 09/08/10 02:59 PM

yes,it is the one you had

got a good deal on it also

Posted By: 68HemiB

Re: single and dual points - 09/08/10 06:22 PM

As has been said before, it's all about coil saturation. The longer the magnetic field has to build, the stronger the spark when the field collapses. The field is only building when the points are closed (the "dwell"). If it were as simple as just setting the gap smaller (so the points barely open), you'd be done. Unfortunately, the smaller the point gap, the more likely they are to arc - you need a minimum gap to avoid the possibility of this happening. Dual point distributors utilize a "make" and a "break" set of points. If either one is closed, the coil is getting juice (effectively increasing the dwell). Only when BOTH points are open does the coil spark. Each set of points are set to a wide enough gap to discourage arcing, but are staggered as to when they open and close. When the "break" set opens, the "make" set is still open (and the coil fires). Shortly thereafter, the "make" set closes (starting the dwell). The "make" set stays closed until the "break" set closes. Once that happens, the "make" set can open (but the coil continues to saturate, since the "break" set is still closed). Then, the "break" set opens, the coil sparks, and we are back to the start of the cycle.

The dwell runs from the instant the "make" set closes through when the "break" set opens.

Decent electronic ignition renders this all moot.