On those tight engines.

They need to get hot (by running) quickly to open up to proper tolerances. If you turn them over cold they will never expand properly and you'll be scuffing off metal that should still be there.

The early ABC engines all had that squeaky fit at the top and a lot of good engines were ruined by guys who wanted them to feel like the older steel liners.

My advice: Fire them up and let them break in on their own.

Andy, nice post on your diesel conversion.