Setting the Points Engine Timing

I read a post this morning about point setting and timing which was somewhat misleading, so thought I'd pass along these thoughts:

As you undoubtedly already know, each degree of dwell angle change at the points will make a direct and corresponding change to engine timing at a rate of roughly 3 degrees engine timing to 1 degree of dwell (depending on the engine design).

Conversely however, engine timing cannot change dwell angle. This is why the method of ‘wiggling it ‘till it sounds better’ timing setting seems to work to your ear, but is also very seldom correct in it’s relationship to the actual stroke of the engine.

Therefore, it is not a bad idea to just 'take a peek' at the timing (preferably just “after” setting the points) to make sure the last guy who timed the engine had his dwell angle set correctly when he timed the engine.

Also, it is a good idea to set the dwell on the low side of the spec (wider gap). This is because as the fiber on the point arm wears, the points are always moving (wearing) closer together (increasing the dwell angle).

The practice of setting the dwell angle low to start with, will cause the wear effect of the points’ fiber rubbing surface to move the points themselves ever closer or "towards" the "correct" setting, then past that correct setting and into the high side of the spec, as the wearing proceeds. Bottom line: a longer period of time in which the points are in correct adjustment.

Another neat trick is to time the engine using a timing light hooked to the coil wire instead of the #1 plug wire. Try it; you’ll like it.

Just some ideas,

Allan

This is not a high performance Chevy engine turning 3500 rpm. Rather most of them turn in the 1400 to 1800 range.

Oh sure. I understand that.

But the statement was made that point setting does not affect base timing. This is incorrect.

Just hollarin' to hear myself hollar, I guess. :>)

Have a good one,

Allan

Dwell is the period of time, measured in degrees of rotation of that distributor shaft, in which the points are closed, thus allowing the field windings in the coil to charge to a sufficient amount to give a good spark at the next collapse cycle.

In other words, it is a "fine-tuning" of the points and is measured with a meter called a dwell meter. The specs are usually given in the tune-up charts and are usually given in a range such as: 27 to 32 degrees, for example.

Remember the little metal “window” on the GM distributor caps back in the days of their engines using points? This was to allow the points to be set with the engine running using a dwell meter and an allen-wrench.

Downside: At the time that our old tractors were born, analogue and digital dwell meters were mostly unheard of; and most of the specs were just given in “thousandths of an inch” gap measurements.

However, given a good distributor with a good set of bushings, these “gap” measurements will correlate very close with proper dwell angles.

The point I was trying to make was that the final point setting does indeed affect engine timing; and more aggressively than what a guy would guess.

This is why it is important to set the points first prior to adjusting the engine timing, because doing it the other way around, allows the process of setting the points to again change that engine timing. Hope I’m making sense here.

Later,

Allan

Hey! Stop with the rock throwin'! :>)

That is not what I said.

I said that the points should be set prior to setting the timing because this setting does indeed affect the timing. I did not say to go back and set 'em again; that doesn't even make sense.

As far as my having read too many manuals, I'm just going to let that one pass.

Geeeeze!

Allan