1st step is the CAM face has been selected
2nd tried to select the rod end (Exhaust Valve) which naturally would be a semi-spherical surface, however this is the result.
The question is what must I do to have the Exh, Valve end follow the surface of the lever action?
I am nearly there with this, next thing to do is have the spring compress - then I feel as if this can demonstrate the operation.
The cam path has to have tangency all the way around. Mate the attached dummy follower to the rod and then use it as the cam path. You can hide it after mating so you will not see it.
Thanks Wayne, I seem to be missing something still, I've aligned the Dummy Follower Planes to the Valve planes as they will both follow the same linear path, as the example below shows the Dummy Follower is the 'Cam" and the Exhaust Lever is the 'Cam Follower'. 
This all worked fine until I added a distance of .437" from the Top Plane of the Valve to the Top Plane of the Dummy Follower, which I'd expected to work. Do I need to make the end Radius of the Exhaust Lever larger?
The cam mate can be flakey sometimes. Probably the best way to do this is by making the bottom torispherical and rflat faces into one face. This can be done by sketching in the fillet and then select the arc and horizontal line at the bottom and doing a fit spline. You can then mate this surface tangent to the cylindrical face of the rocker arm.
Wayne, appreciate your being patient with this octogenarian who is learning this SW, this is driving me 'nucking futts',
I did have the Exhaust Control arm following the cam face, I changed the cam face to start narrowing the 'throw' to what I thought would be appropriate, now this is happening and I cannot understand why. The same issue is occurring at the valve end. (Using the example you sent earlier I changed the valve end to replicate what the valve would look like with a separate part as in your 'Dummy Follower'.
Ken, look at the cam-follower mate in the help file. The cam part has to be a series of tangent lines, arcs, and splines. The follower has to be cylindrical or planar face or a vertex.
http://help.solidworks.com/2019/english/solidworks/sldworks/t_cam_follower_mates_swassy.htm
You need to use a tangent mate for this between the spherical face of the exhaust valve end and the cylindrical face of the exhaust lever.
If you have enough movement of the valve to where the spherical face loses contact with the cylindrical face of the lever and the fillet face does, you would have to do a spline fit like I did with the exhaust valve I uploaded in previous reply.,
Wayne Matus,
HOORAY!!
I had to recreate the Control Cam, and now that works as expected! Thanks to you and my friend Kevin, who tutors me on occasion!
Now everything moves as intended, except . . . . yeah, one perplexing issue as you will see in the attached zip assembly. This mate works for almost one revolution then jumps to the position shown. I have searched unsuccessfully for something that would make this happen. Hope you can shed some light on the cause of this 'jump', as I have noted my estimation is it is treating the follower as a circle and is making the mate to the far side of that circle.
Wayne,
Now have all the CAM mates working. I've recreated each part as an extruded 'spline' that made it all work as intended!
Your thoughtful & patient replies were very helpful.
Next step in my learning process is to get the spring to compress when the plate on the valve moves. Feel free to pass along what ever 'pearls of wisdom' you feel worthwhile. I've watched a few Utube video's on dynamic springs, will do that again and take notes.
Again many thanks!
Here is one that uses the same process that I use. Very simple.https://www.youtube.com/watch?v=kaU1hNM_8RA
Ken, look at the cam-follower mate in the help file. The cam part has to be a series of tangent lines, arcs, and splines. The follower has to be cylindrical or planar face or a vertex.
http://help.solidworks.com/2019/english/solidworks/sldworks/t_cam_follower_mates_swassy.htm
You need to use a tangent mate for this between the spherical face of the exhaust valve end and the cylindrical face of the exhaust lever.
If you have enough movement of the valve to where the spherical face loses contact with the cylindrical face of the lever and the fillet face does, you would have to do a spline fit like I did with the exhaust valve I uploaded in previous reply.,