S&S Cycle Top End Guardian Kit For Big Bore Kits For Harley M8 The S&S Cycle Top End Guardian Kit delivers the reinforced strength an engine demands when big bore and cam upgrades go in. Built for riders who push their machine to the limit, it helps the build handle added power with confidence. Save over 100 when buying the full kit! Features: Rocker Arm Shafts (900-1090) Replace broken or worn OEM pieces with stronger, more durable S&S performance parts Direct replacement for stock parts Hardened and surface ground for ultimate precision and durability Rocker Arm Stud Kit (900-1013) Extend the life of your cylinder heads Prevent damage to Rocker Arm Towers Install studs and safely re-torque nuts Black Oxide Finish 12 pt Nuts Head Bolt Kit (900-1006) Heat Treated 8640 Steel 200,000 psi Ultimate Tensile Strength 14 increases in strength over stock Stronger material than stock Head bolts Durable Black Oxide Coating 9/16 12 point head with integral washer Formed threads Cold Formed Head Reusable Forged Roller Rocker Arms (900-1084) Forged from 8620 steel for greater strength Designed using Finite Element Analysis (Fea) Rollers eliminate thrusting on valves for decreased wear on the valve train Rocker geometry is better suited to high lift cams Bushings are 50 longer than stock, increasing time between rebuilds Larger surface area on the thrust surfaces reduces wear on the heads Oil is sprayed directly on the valve springs, reducing potential for breaking a valve due to over-heating (stock rockers tend to oil the rocker boxes, not the valves) Compatible with stock or S&S CNC heads 1.640 Ratio Capable of .650 max Valve Lift Serviceable and rebuildable for generations of durability A must have for cams with .550 or greater lift!