I got some old rusty X cores and the guides look knurled (looks like a fine thread). Then I read about Olds actually doing this from the factory to promote lubrication. Was that Olds guy BS'n or was that a 1968 Detroit practice? did Ma do that too? I have very little valve play on those "knurled" guides but will probably have them replaced as I need all 16 seats cut to good metal (heavy pitting) and gasket surfaced anyway.
