Posted 08-29-2021 at 16:09:24 [URL] [DELETE]
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Re: Rebuilding Front Mount Distributor 8N - Point Sets
This is from a YT post of 3 years ago:
The cold weekend gave me the time to try and find out why folks are having problems getting new points to open to the required gap of .015. With a lot of help from JMOR, I?m sorry to report that neither one of us can definitively say what the cause is. But, I think we can say with some degree of certainty what is NOT causing the problem.
Please note that both JMOR and I are operating at a distinct handicap of never having personally experienced the problem of not being able to get a new set of points to open to .015.
Our conclusion as of today: it?s not likely the points. It?s the sum total of worn parts in the distributor.
So, please prove us wrong! If you can not get a set of new points to open to .015, pull the distributor apart and start measuring. And then share w/ us what you find.
Now for the detail.
I used new in the box Airtex, NAPA and Bluestreak points. I stacked them one on top of the other on a 3/16? drill bit to replicate the .185 pivot post. There was no discernable, visible difference in the three sets of points.
I could not replicate JMOR?s measurement of the wear block dimensions. Measuring the thickness of the wear block doesn?t tell us anything as JMOR has already noted. The wear block dimension that counts is the distance from the center of the pivot pin to the leading edge of the block. JMOR estimated that at .075 on his set of NAPA points. (below)
From my measurements, I got the Airtex points open to .035, the NAPA points to .026 and the Bluestreaks to slightly more then .035 (biggest feeler gauge blade I have is .035) .
I can offer no explanation for the smaller gap w/ the NAPA points. It must be the adjusting slot in the points base which is measurably different than the Airtex and Bluestreak points. But, I can?t see the difference between .319/.321 and .313 on the NAPA points as accounting for the difference between a max gap of .035 and .026.
My conclusions, based upon some guess work: the critical measurements in the distributor start with the adjusting screw and its free travel. I got a measurement of .244 on the head of the screw and free travel of .032. (I lifted the plate up and measured the distance between the top bushing tower and the screw). Those measurements, plus wear on the cam lobes, bushings and shaft could easily, in my opinion, result in enough slop in the distributor to not allow a gap of .015.
Lastly, as Jock (OR) suggested, I checked the vintage V-8 Ford board (Ford Barn) That's because the dual point Ford V-8 distributor from 1936 to 1948 uses the same design points as does our frontmount. One of the 2 sets is in fact identical to our CS35. While they complain about points quality, no one reported a gap issue. And one regular on that board rebuilds old V-8 Ford distributors and says the NAPA points are the best on the market. Others buy NOS points off of eBay.