The guides are loose from Toowoomba OOTB. I have been told by several people to line the guides to keep from having issues with sticking a valve. These guides are way too loose to run with the Hughes valves anyway, so bronze liners are in the future for these heads.

The valves measure 5/16" on the stem. The guides could be 8 mm, which would be wrong for a Magnum as the are 5/16" stems. No big deal, they were getting lined anyway.