49geezer,
As I remember it, the center oiler is actually through bored the same diameter as the OD of the rocker shafts. It acts as a common distribution point and a shaft support.
The ID of the rocker shafts can plug up something fierce with crud, so this could be a point to check.
I'm pretty sure the proper position of the oil holes in the rocker shafts is 'holes down'. This means the oil exits the shaft in the high wear area on the bottom, and travels to the top and out the hole in the arm.
If it has been assembled with the holes up, you very well could hear a screeching sound, as the highly compressed bottom can't get lubricant.
Restricting the overflow tube is often done, but if all is well and clean with the rocker assemblies, they should get plenty of oil and this 'crimping' won't be necessary.
Stuart
