dwell

If using a feeler gauge, clean it with electrical contact cleaner, and dry it with a lint-free cloth before inserting it between the points. ANY oil on the feeler gauge, even from your fingers, is BAD for the points!

Mark

You're close, but I'd define it a bit differently.

Dwell angle is the amount of "time", measured in degrees of rotation for one cam lobe, that the points are closed, although in reality, the dwell angle is actually the sum of the closing ramp of one lobe and the opening ramp of the next lobe.

The amount of dwell can indeed be changed by the point air-gap, but in and of itself, dwell is not a "timing" thing, but rather, it is a statistic. A measurement.

However, it's preset value will affect ignition timing at the ratio of 1:3 and this is the reason that the points must be set before the engine timing is adjusted.

Bottom line is that dwell is nothing more than just an amount of time and the measurement of this "time" is a more precise way of reading and/or adjusting the point setting vs the “guessing of the air gap” with a feeler gauge.

'Spose ya think I'm splittin' hairs now, right? :>)

Allan

Since they open at the same time regardless of the gap, the wider the point gap, the farther the dist lobe has to travel before they close...so you get a weaker spark cause the time (fill) is shorter. We're on the same sheet.

Mark

Was eating breakfast while ago and thinking about what Allan said about having to reset the ignition timing after tweaking the points, which I had done countless times, I started thinking about mechanisms:

Why is it that you have to do that? Well I got out a sketch pad and ate with one hand and sketched with the other and what I learned (hadn't thought about) was the fact that the ignition does start earlier with a larger gap....like with a .00000 001" gap, the opening starts and stops on just the top of the cam whereas you can open the gap so far that it never closes.....and the difference between these two extremes is distance....of distributor rotation which translates to time (position of dist....hence timing of spark, vs position of piston and other things) and so you affect ignition timing.

So, mechanisms won out again. Proved myself wrong by understanding the mechanism.

Like I always said, if you can understand how it works (mechanism) it's easy to look till you see where it "doesn't work" and there is your problem.

Sorry for the bad info.

Mark

When I was a kid, we called that "float". Same thing happens to valves. :>)

Allan