S&S cams are tested on the dyno, street and racetrack before being offered to the public. With hundreds of test hours on them, you know that you are getting the best cam S&S can produce. Recommend solid or performance aftermarket hydraulic lifters, stock hydraulic tappets are not recommended. Not recommended for stock displacement or lower compression engines. For 88" to 103" engines between 9:1 to 10:1 compression ratio. Best response from 3500 to 6000 rpm. Spring spacing required. Made in the USA. Installer must check coil bind, valve-to-valve clearance, valve-to-piston clearance and cam lobe to case clearance..