Any Advantage of Dual-Point for a Daily Driver?

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dibbons

dibbons

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Would a single-point distributor give up anything with respect to performance to a dual-point distributor for a strictly street/highway application? Thank you.
 
A dual point acts as a Multiple spark ignition if set up correctly with 8 lobes. I like the 4 lobe style by Mallory reduces point float. A single point is only as good as the points you install with good spring tension. But I would use one.

I hate mopar electronic control boxes. Very inconsistent from one to another. I would use a mopar electronic distributor but with a MSD 6AL or better.
 
dibbons said:
Would a single-point distributor give up anything with respect to performance to a dual-point distributor for a strictly street/highway application? Thank you.
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Sure. They are a better distributor, cast iron, and have a ball bearing advance plate. Also the points (in theory) last much longer, because one set closes the (electrical) circuit, and the other opens it. This means the times that the individual points are stressed is half that of single points

The main object of any vintage dual points setup is more dwell angle, which gives more time to magnetically charge the coil. You cannot just increase dwell on single points, because then the opening action would be effectively slowed down, and cause more arcing at the points.

Mopar aluminum single points dist's have a poor history. You used to be able to buy (cheap) bushing kits from Chrysler to replace the dist. bushings. I used to buy them two at a time, as I recall they were less than 7 bucks. But they did require a burnishing tool or reamer to get them properly sized. Also single points are just sloppy, normally. The advance plate is not that stable, dwell changes with vacuum advance. It's been so long I've forgotten some.

The best factory dual points were the tach drive units, which had a ball bearing top bearing. Those things were a HEAVY duty part!!

Back in the 70's when I had the RR (originally a 440-6) I did all kinds of nonsense. Factory dual point, later on had a hemi tach drive dist with a Jones-Motrola tach, and some of the time ran a Tiger or Delta aftermarket CDI--triggered by points. I experimented with the then NAPA Echlin "gold" points, Blue Streak, and Accel I ran the big ol rectangular Mallory coil which was at one time "writ" down on an emissions roadside inspection trap because neither Accel nor Mallory was approved by the CA Air Resources Board. (I was stationed at NAS Miramar, San Diego---"Top Gun", "Fightertown, USA") I also at some point ran an Accel dual point with no vacuum advance.
 
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Put a mopar electronic distributor in it, fire it with a GM HEI 4 pin module and never look back.
 
Oldmanmopar said:
A dual point acts as a Multiple spark ignition if set up correctly with 8 lobes. I like the 4 lobe style by Mallory reduces point float. A single point is only as good as the points you install with good spring tension. But I would use one.

I hate mopar electronic control boxes. Very inconsistent from one to another. I would use a mopar electronic distributor but with a MSD 6AL or better.
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Yes, MP distributor that has the ability to adjust the advance without disassembly, MSD 6AL

Eliminate ballast resistor
Reliability
Fat spark
Rev limiter
Easily adjustable advance
Forget it !
 
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Www.designed2drive.com

Makes this nice little plate to attach a 4 pin HEI module to the underside of a mopar distributor.

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Oldmanmopar I made my own adaptor that uses GM and mopar plugs. I used 3-1 glue type heat shrink to cover it then I bent it 90° before it cooled. On the coil side of the module, I found that a Napa GM SI series alternator repair plug fits perfectly to wire it to the coil. I hollowed out the ballast resistor and put a jumper wire inside so it appears stock and no wiring is butchered in the process. A Pertronix Flame thrower coil has that stock round oil filled coil appearance but is a .3ohm impedance coil with a 50,000V output. This is ideal for this as it looks less "science project" than a GM truck E coil
 
You can run dual point on a street cat my 70 Dart had them stock. Its more maintenance is all you may want to change them every 12 K miles like in the old days...
 
Plus it's hard to get decent points anymore these days unless you luck onto dome old nos blue streak or standard stuff from the 1970s - 1980s that's been sitting on a shelf covered w dust.
 
On a similar subject... Post 8 really got the juices following. Would converting a car that originally had points that has a tachometer have issues with converting to electronic or this GM HEI? If so what would need done to have those tachometers work?
 
I think, as long as it is an electronic tach it would work with either, if it is a factory tach it may be a different setup electronically. I think some of them weren't elctronic also. Most tachs are hooked up to the negative side of the coil and they sense when the field collapses.
 
dibbons said:
Would a single-point distributor give up anything with respect to performance to a dual-point distributor for a strictly street/highway application? Thank you.
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IMO yes, but maybe not for the reason you think.
If you have a good one WITH a vacuum advance, you can install a high current coil and open up the plug gaps to .055 (or more). This will allow you to lean the cruise circuit out, and then give the engine the timing it so desperately wants; bottom line is more cruise torque and more importantly more steady-state MPGs. And probably less oil consumption and longer lasting rings.
The Big Yellow square-top Accell SuperCoil comes to mind. It helped one of my combos achieve over 30 mpgs; allbeit with electronic ignition, and double-overdrive..
 
The only advantage of dual points is at higher rpms. If this is just a street cruiser, then using a DP dist just adds complexity...& something else to fail.
 
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