BChevy Big Block Jet Boat Above Transom Exhaust Header Kit - BBC V8 ReviewbP PP Chevy Big Block Jet Boat Above Transom Exhaust Header Kit - BBC V8 PMade of high quality steel with 2-pieces 4-1 (8-2-1) direct bolt-on designPTIG welded CNC machine flangePO2 sensor bung insertion Metal gasket included Inlet: 2.25" Outlet: 4" Non water injection ports above transom headersPIncrease high flow air, instantly gain 10 to 15 Hp.