In Reply to: Points Dwell For Ford Tractors posted by BeeMO on July 27, 2010 at 11:20:28:
IF you set the dwell as high as 50 to 60 degrees, you then will be running an appreciably smaller point gap than 0.025 inch. My own experiments indicate about 8 to 10 degrees for every 0.006 inch gap delta (change). Therefore an increase from a nominal 36 degrees to say 56 degrees should result in a gap decrease from 0.025 to (0.025 - 0.006 X 20/10)=0.013 inch. I expect that the gap reduction might very well result in shorter point life and reduced spark energy due to greater arcing across the smaller point gap. Sounds like you are happy with your point life and operation of your tractor....if so, keep on keeping on.
I have never seen a dwell spec in an official publication for the 8N side mount, however, the FO-4 does give dwell numbers for the front mount as 35 to 38 degrees and this is in good agreement with the Ford Dealer Service Training Manual which states dwell as a percentage instead of in degrees, as 39 to 42.5%, which equates to 35 to 38.5 degrees.
There is a Jubilee/NAA spec that states 35.5 to 39% (0.025 inch), however, I expect that the % notation is an error since it is so close to the degrees numbers for the 8N-front.
Even if it is correct as 35.5 to 39%, that equates to 32 to 35.1 degrees and is nowhere near the 50 to 60 degree range.
If you like to play, you might try doing an 'as accurate as possible' 0.025 inch point setting on a distributor with excellent bushings, and then read the dwell. Of course, as old as these machines are, there is no telling what wear has done to alter things!
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