EDELBROCK #60459 PERFORMER RPM O-PORT CYLINDER HEAD FOR BIG-BLOCK CHEVY. The Edelbrock #60459 Performer RPM O-Port cylinder head is designed for Big-Block Chevy applications. The Edelbrock #60459 Performer RPM head is perfect for street performance, daily drivers, street rods and muscle cars where seat-of-the-pants performance is needed. This cylinder head delivers great throttle response and power from 1500 to 6500 rpm. They also feature the highest quality intake and exhaust valves and valve springs. For use on pre-pollution controlled vehicles only. Exhaust 45 deg/Intake 45 deg. EQUIPPED WITH SPRINGS FOR USE IN HYDRAULIC FLAT TAPPET CAMSHAFT APPLICATIONS. Match with Edelbrock head gasket sets. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4 reach with flat gasket seat. These oval port heads will support over 540 hp with 9.5:1 compression when used as part of the Total Power Package®. Unique oval intake port shape produces flow similar to rectangular ports, but the smaller port size provides excellent seat-of-the-pants performance and crisp throttle response. Semi-open chamber design maximizes efficiency with streetable compression ratios. Smaller-than-stock 11/32 valve stems promote excellent flow and lighter valve weight. (Suggested) 0.4375 in. Valve Spring Maximum Lift. Instant response to any inquiries. If you are not sure this is the correct item for your car, you can send us VIN number of your vehicle, and we will check it for you! If you have any questions about this item, please ask. DEFECT/DELAY If there is any defect or delay? Items should be installed by authorised mechanics. Other destinations might have different tariffs or additional extended area cost. If You live outside Europe? If You have received damaged or faulty goods? United Kingdom, Italy, Germany, Latvia.