Dual Points
Points are limited
by their mechanical properties. To get a hotter spark you need to pull more amps. Points
can only handle about 4 amps. Because breaker point systems have a high primary resistance
you need more dwell time to reach 4 amps at higher RPMs. Dual point distributors use two
sets of points slightly offset to increase the dwell. Since they are offset they can also
have larger point gaps. A standard Ford single point distributor has about 28° dwell with
a .014" point gap. A Ford dual point has 33° with a .019" gap. It doesn't sound
like much but it makes a big difference. I could feel a noticeable improvement when I
converted my single point distributor to a dual point. Since a dual point has larger point
gaps it also needs higher breaker spring tension. The factory spec for a Ford dual point
is 27-30 ounces.
Adjusting a dual
point is a little different than single points. You need to isolate one set of points at a
time to make sure they are both set to the same dwell. You also need to make sure the
combined dwell is within spec. My uncle showed me a great way to adjust a dual point
distributor. Hook a remote start switch to the starter solenoid and a dwell meter to the
distributor. Pull the coil lead off the distributor cap and ground it to the motor. Pull
off the distributor cap and rotor so you can get to the points. Place a thin piece of
cardboard or plastic between one set of points so they don't make contact. Turn the motor
over with the remote start switch (make sure the car is out of gear first) and read the
dwell. Then move the cardboard to the other points and measure the dwell again. Adjust the
points as needed until both are the same when isolated and give you the proper total dwell
when combined. I adjust mine to 26° each which gives me a total of 33°.
Dual points used to
be the best low buck ignition but now they are getting harder to find. I bought a used
Accel dual point for $20. It was poorly built, I couldn't get a stable dwell. I shimmed up
the shaft but the breaker plate would move around. I got rid of it and bought a Ford dual
point for $75. It's a '73 Cobrajet distributor with vacuum advance. I removed the breaker
plate and cam and put them in my 289 distributor housing. Can you say sleeper? It
is built much better than the Accel unit, I get a rock solid dwell. Most factory dual
points cost over $100. Not exactly a low buck speed part. These days an electronic ignition can be a cheaper alternative.
For those of you who
are anti-point and feel I'm wasting web space for even mentioning them, please send hate
mail to mrriggs@gofastforless.com. The rest
of you, who don't believe everything you read in car magazines, write me at mrriggs@gofastforless.com and let me know what
you think.