Ref. cams and followers,
it's generally not advised to run new and old cams/followers together, though you can usually get away with it. The reason is that the contact stresses are pretty high as the cam goes over full lift, and there is a reversal of oil entrainment (getting technical :oops: ) where the cam reaches the edge of the follower (maximum valve velocity).
These conditions can result in what's termed boundary lubrication where you're simply relying on a few molecules of oil to keep the metal apart rather than a nice thick oil film generated by the surfaces sliding over each other.
New parts are manufactured with surfaces which bed together during the first few hours running, like rings and bores, but retain enough oil to avoid scuffing.
If you're putting used and new parts together, use some very fine silicon carbide paper (wet&dry) to put a cross-hatch pattern on the cam/follower surface (like cylinder honing), at 45deg to the direction of sliding. Buckets/biscuit shims usually have a similar spiral type hone pattern. This gives a reservoir for the oil to sit in. Wash parts very thoroughly afterwards, put tape over drillings etc to avoid grit getting into oilways.
For assembly use either special cam assembly paste available from decent tuning places, or a small amount of EP type gear oil will provide protection for a short while after start-up. Whatever you use, make sure everything is oiled well.
Lubrication is worst and stresses highest at low speed like idle, so once the engine is started, increase the revs to around 3000rpm as soon as you can. Other than that there's little you can do for valve train other than give the engine a few hours running around mid-revs. Don't leave it idling.
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