I was looking back and found this discussion on setting points so I thought that I would offer this option. When I set points I always use a dwell meter with the distributor cap and rotor off and have someone turn the engine over and I adjust the dwell while it is being cranked over. Works on the stock 8 lobe and my old Mallory 4 lobe distributors.

  Vic Correnti

Switching off one set (to retard) would also ease starting when running extreme initial advance. Great idea!

6 VOLTS/POS. GRD. NW INDIANA

Any variation or inconsistencies ocurring in the point gap will be detrimental to overall performance.  Poor idling characteristics usually come to the top of the list.

 

On a typical dual point setup, the breaker points are staggered which results in only one set of points actually controlling the timing of the spark to the plugs.  The remaining set of points simply allows the dwell time to be longer so that a better spark at higher rpms can be generated.  An old practice when dual point ignitions were the rage was to simply swap the points to be able to use the set that hadn’t been arcing to save a couple of bucks.  For myself and because the points were staggered, I would wire both sets so I could turn one set off upon going into 3^rd gear (427 Fairlane) and allow the ignition timing to retard about 4°.  This allowed me to run an additional 4° advance in the lower gears.  That’s just food for thought for those of you that are looking for that additional edge at the dragstrip and are actually running a dual point distributor.

 

The Mallory Rev-Pol or Double-Life distributors and Grant Flamethrowers are dual point but are not of the staggered design.  On these, the breaker points are phased 180° apart and each do equal work.

 

Converting the distributor to electronic ignition would reduce some of the pain of what you’re going through as the air gap would not be as critical in regards to a bit of variation taking place.  An even better solution although more expensive would be to just purchase one of the new aftermarket electronic distributors for the Y.

Lorena, Texas (South of Waco)

Guess I answered my own question (since no one chimed in to tell me the laws of physics changed this week). Timing variation due to unstable point gap CAN'T be good on a precision engine. I will bite the bullet and change the shaft.

6 VOLTS/POS. GRD. NW INDIANA

Ted,

Finally got around to measuring lobe/gap variation of installed NOS AutoLite distributor shaft I got on eBay (.003"). The tallest lobes are directly opposite the shortest and progress in order of height, which leads me to believe the shaft was dropped/bent at some time (more likely than machining/manufacturing error?).
I COULD re-install the original shaft, as the bushing clearance & end-play was within spec., but the cam is a bit rough/scored (reason I changed it). Or, I could find another NOS shaft and hope IT is not defective, but the trouble involved in replacing is something I would really like to avoid, especially since the resulting end-play seems to be a bit of a "crap shoot" after the drilling/pining operation.

Question: Since the distributor has a dual point plate, I wonder if the effect of lobe/gap variation will cancel out? The dwell should not vary much as the points are near enough to 180 degrees apart, but gap variation might likely cause the timing to jump around?
Since this distributor is meant eventually for a balanced motor I am assembling, it would seem any timing instability would be especially detrimental?

Opinions?



6 VOLTS/POS. GRD. NW INDIANA

Charlie,



Dwell meter on Sun machine needs re-calibration, but reads steady. Dual point unit I am setting up has dwell to spare, so will want to error toward wider gap and avoid burnt points.



Ted,



Indicator shown has side-lever action (nothing like it in any of my machine tool catalogs). Mounts to upper edge of dist. body.



P.S. I had overlooked .002" lobe/gap tolerance recommendation in follow-up article.

6 VOLTS/POS. GRD. NW INDIANA

Got a dwell meter?


Lawrenceville, GA

crenwelge,



Loadomatic, with fresh bushing and (70s era?) NOS Motocraft shaft, so no lobe/bearing wear issues.

Silly me, I just assumed the shaft/cam was a precision machined item, and merely setting the point gap on any lobe would suffice.

I kept thinking the points screws were loose, since whenever I spun the distributor on the Sun machine and rechecked the gap, it was way off. How far off is yet to be determined.



Ted,



Indicator tool depicted in back issue of "Skinned Knuckles" mag. Sure would simplify gap setting chore (I've been spoiled by the P&G valve gapper), plus would avoid feeler gauge error inherent with metal transfer/pitting that prevents accurate gap determination as points wear (much like rocker/stem clearance).

6 VOLTS/POS. GRD. NW INDIANA

Daniel.  I have a collection of odd ball tools that simplified setting point gaps but a dial indicator for that purpose isn’t one of them.  That sounds like one of those items that I just didn’t come across back in the day of doing daily tuneups on point ignitions.

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My own tolerance would be 0.003" but haven't seen an official specification variance on that in awhile.  Sloppier than this will obviously still run but running nuances as well as hard starting will start surfacing.

Lorena, Texas (South of Waco)

I have never seen a lobe wear out because the rubbing block wears. Bearings on the distributor shaft can cause erratic point gap. This can usually be felt by wiggling the shaft. If you are suspecting something wrong with your distributor, I would take it out and see if there is play in the shaft. If you are wondering about lobes, you could measure the point gap on each high spot with a feeler gauge. Is it the old load a matic or is it a 57 or later?

Kenneth

Fredricksburg, Texas