1966-'84 big twins SH-Series engines. S&S® rocker arms for shovelhead engines are machined from 8620 steel forgings and heat treated for maximum strength. The forgings are designed to eliminate stress points and provide the strongest, most durable rocker arm possible. These roller rocker arms also feature the exclusive .750" long S&S® rocker arm bushings, with 50% more load bearing surface than stock .500" bushings. An oil passage from the pushrod cup of the rocker arm to the inside of the rocker arm body allows top-end oiling through the pushrods when used in conjunction with S&S® billet tappet guides and S&S® Quickee pushrods. Oiling can also be done through the stock 1966-'84 external oiling system. Nominal rocker ratio of 1.5:1. The roller tip reduces valve tip wear and side loading of the valve stem in high lift applications. S&S® roller rocker arms are compatible with S&S® billet and stock rocker boxes. Some clearancing may be required when using stock rocker boxes.