1983 hydraulic engine

If you do take them out, I would soak them overnight in kero first to get rid of any varnish that wil cause them to stick; and then oil them. Work to get the kero completely out; taping thme upside down on a board for a while will do it. If you see a lot of gunk coming out, then re-do the kero 'til clean. In both cases, immerse the lifter completey in the liquid and take a pushrod and pump the lifter piston rapidly a lot to work the fluid into the lifters.

Make sure the lifters stay exactly in order; swapping any of them pretty much is a gurantee for wiping out one or more cam lobes. You can usually put in a new lifter on a used cam but never an unmatched used lilfter on a different lobe anywhere.