it was an 1/8" hole (in the bolt). early or late (I forget which) had the bolt w hole & the other (early or late) had the drip tray that elim'd that bolt. that is drip oiling & for the ultimate you could drill a .015 (1/64) hole in an alum NPT pipe plug & drill/tap/thread it into the front of the pass horizontle oil gallery & a 3/8 hole in the cam plate for it to squirt out onto the chain. Shorten this pipe plug as to not block off oil down to the #1 main/drivers side gallery (that would be disastrous!). Maybe the chain gets enough splash as is but its fun to mod things & evidently some was needed cuz Ma did the drip oiling. Do the same (.015) in a 3/8 alum pipe plug next to the intergear at the other end/side.