I have a 261 head bolt question. Evidently some 261s have a head bolt that is drilled for oil passage as I have read on other posts.I want to be sure what I think I have figured out.Someone who knows please confirm or correct me.According to the old Chevrolet parts book this special bolt is larger in diameter than the other head bolts in the same engine.1/2-13 compared to 3/8-13.Im figuring it will be obvious where the special bolt goes by one hole in the block being bigger.Right?Also if using a 235 head on a 261 will one hole in the head need drilling oversize or are the holes in the head big enough as is?Thanks.
