Hollow spindle cams

[Steve Little]

Hi.
I was looking at a couple of cams trying to decide what cam I would use for a 38 EL Bobber that I will be building in the new year.
I believe both of them are "OEM" hollow spindle cams.
While inspecting them, I noticed that the lightning cam has more lift and duration.
Can anyone give an approximate date of introduction for each of these cams?
See attached pictures:

The solid gear cam has "1F" stamped in the gear

[vph-d]

Wasn't the Lightning cam used on the 36 models?
VPH-D

[Rubone]

There are more than one type so called "lightning" cams. The original type from '36 had more lift and duration. It was changed either mid year or for the '37 model year to the same profile used throughout Knuckle production supposedly due to hard starting and rough idle. The drilled gear was used for several more years before going to the solid type. When the changes actually occurred I do not know as I never gave it much though back when there were still lots of Knuckle motors around.

[knuckleheadtim]

You might try both to see if one gives a better fit on the gear. I'm convinced the factory hand selected gears for correct backlash, as original motors always seem perfect, whereas those assembled from parts have varied gear lash. A tight fit will whine, and a loose fit will rattle at low speeds.

[Chris Haynes]

The early '36 cam had problems with backfire during starting. To fix this they retarded the timing roughly half a tooth. The lift and duration remained the same.