[Farmall] Slow Cub Oil Pressure

[Roger Moffat]

My Farmall Cub - serial number right now is out in a dark barn - but  
one of the earlier ones I think maybe around 1950? - has trouble  
getting oil pressure when I first start it up, particularly if it has  
sat for a week or two or three or more before I want to use it. It  
can take quite a few minutes to get pressure going with it running at  
idle - even after I take the oil filter top off and empty an oil can  
into it. Once the pressure arrives, the rumbling and knocking and  
tapping in the engine stop, and the pressure is nearly to the right  
side of the gauge at not much above idle speed.

I know that in general the whole thing is "tired", but is there any  
suggestions of things to look for that might at least improve the  
situation before I think about having to tear the whole engine down?

Thanks

Roger