oiling bolt was the stock 5/16-18, drilled with a 1/16th bit. Lots of oil pumps through. Also have hollow pushrods and the lifters feed oil as well (although kinda pointless since it just stops at the adjuster). Shift rpm 6000-6500(when racing) haven't shifted higher.
These are all the stock sized bolts. Pulled the thread inserts right on out which allowed the hardened shaft to flex.. and snapp a roo.