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nivek123:

Dwell is an electrical performance measurement made on an operating distributor by means of an instrument called a Dwell Meter.

Divide 360 degrees of distributor rotation by the # of cylinders your engine has. Of that result, dwell is the number of degrees that the points remain closed, meaning the # of degrees during which the coil is energized. Adjusting to a dwell angle specification is just an alternate way of adjusting the point gap. Dwell should remain essentially constant regardless of engine speed; beyond just a degree or two or three, failure to do so is indicative of mechanical problems with the distributor.

Here are some pictures. The first picture is of a dwell meter. Hook the red lead to the positive post of the coil and the black lead to the negative, start the engine, and read the meter. The rpm switch is there as an aid.

The second picture shows a reading on a meter.

Suppose you took your car to someone you know and he says: " I don't have one of those, but I do have a multi-meter for modern cars." If he hooks his meter up the same way and switches it to Duty Cycle he will get the percentage of time the points are closed - Dwelling. Multiply that percentage by 360 and divide by eight and you have the dwell angle. Of course you need only check that Duty Cycle remains relatively stable when you raise the RPM to determine if the distributor is worn.

I have a KAL 3000 multi-meter which has a dwell setting and can do the Caddy 12 and 16 as well as Packards. They show up on junk bay and are cheap because nobody wants them. KAL equipment was a competitor to SUN.

Attached is a picture of a distributor tester in action. The rebuilder will expect to see the lights remaining in position and not jumping around as RPM is increased. The timing advance mechanisms are checked by reading the position of the lights as RPM is increased. I love those old machines and those big engine analyzers. One time I was working on a car and the owner got pissed off that I sent the distributor for repair. I didn't hear anymore complaining when the motor would start in 1/8 turn when it came back.

Attach file:

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  Dwell Meter.jpg (134.19 KB)


  DwellTachScale.jpg (39.01 KB)


  Distributor machine.jpg (33.07 KB)

Thank you so much . I now have a place to meditate on what you just sent me to get to an understanding of the distributer and the performance of the engine .
are there any books that would describe in detail what you just explained ?

Any vintage Chilton manual or look up the Packard employee training manuals on this site.

A demonstration is probably available somewhere on junktube.

In the literature section on this site is a great ignition training manual - very, very helpful. I've used it several times. Good luck!