Camshaft knocking problem

[Bob from Northport]

We have been in the process of installing a new engine into a 1928 Fire engine. The engine was purchased from a rebuilder, unnamed for the present, not showing much concern about this problem. The final assembly was completed yesterday, and the engine started very nicely. But the loudest knocking noise we have ever heard also appeared upon starting. The underside of the engine was taken apart today and checked-no problems with bearings or torque. We disconnected every item on the engine attempting to locate the problem. We finally located the problem with the camshaft. We removed the side cover plate, and ran the engine, and watched the camshaft move in and out toward the front of the engine. Suspecting the spring and plunger inside the timing cover, we removed and replaced it with new ones twice, only to see the same movement and noise appear. When hand cranking/moving the cam and crank, the camshaft moves outward toward the front of the enigne .035 on one side, then moved back against the engine casing. This is with movement VERY SLOWLY!
1. Can anyone offer reasons why the camshaft would move that much when barely moving?
2. The plunger/spring is not strong enough to stop the movement-why?
3. Is this a problem with the camshaft regrind?
4. Since the only thing that comes in contact with the cam is the oil pump-distributor shaft gear set up-could this be causing the problem.
We don't believe another spring/plunger will do any better.
Any thoughts Mr Endy? How about the rest out there. This is a totally free job to the village that owns the truck. We could use the help.
Thanks!!
Bob's Model A Ford Garage Bob Campbell