View Full Version : Ignition: dwell time in degrees on Pertronix ignition.

07-23-2017, 09:16 PM
I use a Pertronix Ignitor on my Studebaker 259 V-8. I converted it over a couple of years ago when I had the distributor out. Set the gap and installed distributor. I did not check the dwell angle until today because there is no adjustment to be made. At 650 rpm I only have 7 degrees of dwell. When the speed is increased it will increase to about 20 but drops back to 18 as RPM climbs over 2500. I think my dwell meter is functioning properly. I have had it for years and it has always done a good job verifying point gap. Am I missing something? Can I, or should I be using my old meter to measure dwell angle on an electronic unit? I am wondering if at high speed my coil is going to get enough energy to function properly with only 7 degrees of dwell. My dwell meter is set for 8 cylinder by the way. I know the electronic unit switches on and off much faster then the standard set of points can but according to what the manual states I should be reading about 28 degrees.

Joshua Skinner
07-24-2017, 12:15 AM
You don't need full dwell at idle. Ideally you'd have the dwell continue to increase with RPM to give the same coil on time, but there is a limit. It's been a long time since I looked at an ignition scope so I don't have a good idea of the practical limit. Does the dwell continue to drop after 2500 RPM?

07-24-2017, 12:47 AM
Does the engine have full power at all RPM and is it running cool?

07-24-2017, 01:54 AM
Dwell angle is kind of meaningless with electronic ignition. In points ignition "dwell" was a measure of long the points remained closed, allowing a magnetic field to build in the coil. Dwell to small; strength of magnetic field suffers, spark gets weak.

An electronic ignitor is basically just a trigger, and coil charge time is as large as it can be. I wouldn't expect the dwell meter reading to be accurate.

07-24-2017, 07:15 AM
Gordr has the answer,drive the car and enjoy it, don't" dwell" on the dist. operation. the only Pertronics drawback i can see is the hiding of the rotor shank. you cant see a split rotor and you go nuts trying to figure out why the project wont start, just sounds like a brand X thats jumped time. Dont ask me how i know this please! Luck Doofus

07-24-2017, 08:43 AM
The last time I checked the dwell on a Pertronix equipped V8 distributor, it showed 24 deg at idle and didn't change as the engine rpm was increased. The newer Pertronix 2 and 3 supposedly have a variable dwell time built into them, but I haven't checked to see if that claim is true. Bud

07-26-2017, 05:05 PM
Evidently I have enough dwell over 2500 rpm. The engine does not seem to lose power. I have never drove the car with standard ignition so I was just wondering if there was more power that could be made.

07-26-2017, 05:42 PM
If the engine is running well, don't worry about it. I doubt that you will see a difference in power between the Pertronix ignition and a standard points ignition if the points are in good shape and the dwell is set correctly. The big advantage to the Pertronix ignition is greatly reduced maintenance on the distributor. Bud