Primarily designed for stock replacement applications where traditional looks and improved performance are important. These cylinder heads are made from the same high-quality aircraft-cylinder head material like the Evolution heads. The intake port is the same diameter and is positioned in the same location as stock which means stock manifolds bolt right up. A directional vane like the one used in S&S Evo heads to route the air around the valve stem and guide area is located in the floor of the port. Standard intake valve diameter is stock at 1 15/16“. The combustion chamber is identical to stock enabling installation on any engine with hemispherical domed pistons. The exhaust port is also stock configuration and readily accepts stock style exhaust systems. Standard exhaust valve diameter is also stock at 1 3/4“. The pre-installed .590“ lift valve springs are used for greater cam lift versatility, the valve seats are compatible with present day unleaded fuel. Although these heads for Shovel big Twins are designed for stock replacement applications, flow characteristics have been improved up to 9% more flow. S&S Shovelhead cylinder heads easily bolt on and fit like stock. Frame and other clearancing problems are non-existent. Exhaust systems with stock dimensions can be used. Stock rocker cover assemblies are not included and are installed using hardware provided. They are available as stock replacement and as a 2-plug version for 3 5/8” Big Bore cylinders. Each High Output Super Stock Shovelhead cylinder head kit includes front and rear cylinder heads completely assembled with valve seats, valve guides, valves, valve springs, spring collars, valve keepers and valve guide seals ready to run. Also included are gaskets required for installation including cylinder base and head gaskets, rocker cover and exhaust port gaskets, rocker cover and exhaust pipe mounting hardware and installation instructions.