BE SURE YOUR YORK/TECUMSEH HEAD HAS THE 'ROTOLOCK' FITTINGS. INTEGRAL HEAD 'ROTOLOCK' FITTINGS. Integral (1"-14 )Threaded Fittings On Head. Blue Used On Suction (Low) Side, Female 1 X 14 Threads, To Allow Hook Up of Suction Hose(#10 O ring fitting) and Servicing of System.