The most common cause of air compressor failure is carbon accumulation in the discharge line resulting in damage to the air compressor head assembly. Replacing the head assembly requires less down time than replacing the entire unit.All Heads Listed Compress 18.7 of Air CFM (Cubic Feet per Minute) All Head Assemblies Include: • Assembled Head (Including Unloader Assembly) • Torque to Yield Bolts • All Valves & Gaskets • All Ports (Unless Noted): STOR; Straight Thread with O-Ring Boss Installation Information: Maybe found in Bepco’s Wabco Air Compressor Information & Components Catalog at www.bepco.biz/products/air-brake-systems. Model: Wabco SS318, Bore Size: 85MM, Water Port: 3/8" NPT, Discharge: 1/2" NPT, Governor Port: 1/8"-27 NPT, Compressor Application: 9111535400X, 9111535410X, 9111530550X, 9111530560X, 9111530557X, 9111530567X, 303GB5129M, 303GB5129M2, 303GB5129AM