Dwell should be 30-34 degrees depending on how you set the points. I usually pull em' in at around 30-32 on the 504 machine after I rebuild our customer's Distributors. A .020 point gap usually dwells out around 29-30.  HTH.  I might add that a good set of points will hold solid around 2200 rpm.  I use SMP's Blue Streak points in all my Distributors unless I'm building a Distributor for a customer that wants an E.I. installed. (the better way to fly)

Steve@B&B

ACinSC wrote: ... Could a worn out distributer cause the timing mark to drift when checking it with a timing light? Thanks again

Yes.

Also wear in the gear train driving the distributor.

I prefer setting the points/dwell toward the max because the rubbing block wear will tend to decrease it.

If it runs well enough to satisfy you then don't sweat the petty stuff.

ARRGGHH!

Brain cramp!

That's confusing 

Set the points toward the max opening, which will be minimum dwell; as the rubbing block wears, the gap will decrease, thus increasing the dwell.

Sorry about that.

ACinSC wrote: Think book calls for.022 point gap, so as it wears gap gets smaller and dwell increases? That is confusing. Thanks Les

Correct.

Dwell is the amount of degrees of rotation that the points are closed; the longer the points are closed the more time available for the coil to saturate (not really a problem on low-speed engines like our tractors).

If the points are barely opening, like say 0.005" the dwell would be quite high, if the ponts were opening really wide like 0.060" they may not even close at all, and if they did the dwell would be very low.

Dwell is really just a means of checking the gap without needing to open the distributor cap.

You can also check the condition of the points with a good multimeter.