They should slide easily, however they are a perfect machined fit, so they should not be sloppy. It should not provide any resistance on the plunger.
If you are tearing head o-rings, you need to clean up that edge of the pump before you put it back together next time. I have taken a head a off a pump nearly 10-12 times with the same o-ring.
Thank you very much for the response.
Perhaps I should explain my scenario in more detail. I am figuring it out more as time goes along what has happened...
The internals have been sitting in stagnant diesel fuel for well over a year. They are still perfectly good parts, but most are covered with thick, sticky, dark sludge from the diesel. I don't know what it is.
So I have been soaking and cleaning every piece with a toothbrush using lacquer thinner and then setting back into fresh diesel.
Upon re-assembly everything went perfect except getting the distributor head back on and the control collar / control lever was really binding up big time.
The control collar's (what seems like) .00001 fit had gotten gum'd up pretty bad I guess. I was turning over the pump, and the control collar was moving with the plunger, moving all the throttle arms,etc...
I knew this wasn't right HA! Anyways, I did this two times thinking I had gotten it freed up the second time, but it wasn't enough still.
I had to use a
lot of force on the plunger plate to push the collar off and clean everything, it was stubborn to get back on because it is machined so perfect like you said.
Now it is actually moving on the shaft with consistent force up and down, but still feels excessive.
I think the O-rings got messed up because since the control collar was stuck, the spot on the back where those top 2 springs in the distributor head tighten against was basically not moving.
So tightening torque for the top part just kept increasing the more I tightened the head down. Thus removing/installing was not possible to do uniformly due to the forces involved leading to skewed and torn new o-rings. I had to gently pry the head off both times with a screwdriver all the way around to get it to pop off. I had all the bolts out of the head, and you could see the top part pushed out more of an angle than the bottom. That is my theory at least. Does it sound plausible?
I'm also really surprised that little ball joint didn't break how much I must have tightened it down the first time. I think it might have helped loosen it up too actually.