The Edelbrock #61767 Performer RPM Bare NHRA Stock/Super Stock cylinder heads are designed for use with 1992 & later 5.2L (318 c.i.d.) and 1993 & later 5.9L (360 c.i.d.) Chrysler Magnum style V8 applications. These cylinder heads deliver great throttle response and power from 1500 to 6500 rpm. Cast and heat treated at the Edelbrock Foundry and machined at Edelbrock's manufacturing facility in the USA, Edelbrock heads are the best in quality and performance. All Edelbrock Cylinder Heads are designed from scratch using the latest in computer technology by our own highly skilled engineer's. Using highly efficient ports and state-of-the-art combustion chamber shapes, Edelbrock cylinder heads offer improved performance throughout the rpm range for great throttle response and top-end horsepower. Top-quality features include threaded inserts in rocker stud and exhaust bolt holes for superior strength and durability, and manganese-bronze valve guides with ductile iron valve seats. These are features that some other companies don't include!INSTALLATION NOTE: • Bare heads will have valve guides & seats installed, but will require final sizing & a valve job to match the valves you will be using. • Match with the Edelbrock RPM Air-Gap Magnum manifold #7577 • Cylinder heads exhaust flanges in stock location to allow use of stock exhaust if desired • Accepts small-block Chevy adjustable 1.6 ratio rockers and classic valve covers #4177 and #41773 • Requires hardened pushrods, #9638. • Match with Edelbrock head gasket sets. • Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat. • Deck thickness: 5/8" • Rocker stud diameter: 3/8" • Pushrod diameter: 5/16" (width of slot in guide plate).