High Compression Aluminum Head, High Style for use with high radiator. Uses standard size model T spark plugs. This head has complete original appearance when installed. "Z" style combustion chamber. 6 to 1 compression ratio and extra water capacity, adds approximately 7 HP, use only with stock pistons and stock T spark plugs. This head cannot be used with high compression pistons. No modifications to your engine are required. Uses standard Model T head gasket. Note: Low style heads are 2" tall and high heads are 2.5" tall. This is the measurement from the head gasket surface to under the head of the head bolt.