The hipo distributor has a 8 sided cam that opens and closes the points. Understand when points are closed, the coil is building energy and when the points open, the coil discharges the energy to the appropriate spark plug. Looking at the flat spots on the points cam, the flat spot is not completely flat. It has a very slight rise in center between the high points on the lobe. Looks like the slight rise would start to open and close the points before they reach the point when they are supposed to open. Almost like pulling bow string back 3/4 of the way before it is pulled all the way back. What is the function/purpose of the slight ridge between the flat spots?
Very similar to engine cam design. A rapid open/close would increase point "float" at lower RPM. The high performance engines used a point set with higher tension to help prevent "float". They need a gentle ramp to both open and close.......does that help?
Thanks Dizzy
Appreciate the analogy to cam lobes. Helps me understand why the crest is there.
To add to that , the hi po distributor cam IS different than a single point cam. A company I worked for in the '70's used to regrind single point cams to dual point cams for a local company, Carex , that offered dual point conversion kits for Fords. The rise in the 'center of the flat" was to control "point surge" ( flex ) at high rpm as the point closed.
Randy
If I had a single point cam sitting next to a dual point cam, what differences would I be looking for?
The quickest way is by the two advance slots. One is 10 and the other 13 on the dual point cam. The cam itself is tough to see any difference on. It will show up on a distributor machine though. The actual difference is as I mentioned ( and others) the small rise and on the peak of the high points. They are ground to create the specific "dwell " time as both pairs are open with different opening and closing points. A single point cam as all of the "open time" ground into "one " high point instead of two.