The Edelbrock part # 77139 Victor Jr. LT1 (Gen V) cylinder heads are an excellent upgrade for ultra high-performance on GM Gen V LT1 racing engines. The biggest change and advantage of Victor Jr. is the revised exhaust ports, which have been moved 1.5" horizontally to improve air flow. This revision will require the use of custom exhaust manifolds and headers. They have been designed with high flow intake/exhaust ports and back cut intake valves for improved air flow. The valve position has also been revised to accommodate interlocking valve seat rings and larger valves. The intake valve has been increased to 2.20" diameter and has hollow stem valves with a 45° seat angle, while the exhaust valve has a diameter of 1.60" and utilizes a 50° seat angle. It's designed with a thicker deck and more material in the intake, exhaust and port walls for improved strength, durability and for additional porting and deck milling. This cylinder head features fully CNC machined intake ports, combustion chambers and exhaust ports for improved performance. The Victor Jr. retains the stock rocker arm, intake port and spark plug tip location for use with factory components. Like all of our other cylinder heads, these have been designed, tested and cast from 356 aluminum and heat treated to T-6 specs in our facilities in Southern California to guarantee you get the best from a name you can trust. Looking for custom LT1 headers? Please contact Kooks Exhaust and Headers at (866) 586-5665 for more details about their LT1 headers for the Edelbrock Victor Jr. cylinder head! INSTALLATION NOTE: Match with Edelbrock head gasket sets. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat.