The Edelbrock #61329 E-CNC LS3 Cylinder Heads are a great general-purpose high performance cylinder head for any street- strip LS engine. These cylinder heads have a high velocity port compared to stock LS3 cylinder heads, making them an ideal upgrade for any cathedral port or 3.89" bore LS application. They feature an improved design and casting that gives cylinder head porters more material to work with compared to stock heads. Like all of our other E-CNC cylinder heads, these feature fully CNC'd intake ports, combustion chambers and exhaust ports for improved performance. Compatible with stock style rocker arms.INSTALLATION NOTE: • Designed for use with LSX Blocks • Match with Edelbrock head gasket sets. Recommended spark plugs are Champion RC12YC or equivalent 14mm x 3/4" reach with flat gasket seat.