Knight Prowler TW6H Twin Cams (Pack of 2) Hi Lift Valve Springs Required .053 Timing INT 20/40 & EX 42/18 Duration .053 INT 240 & EX 240 Valve Lift INT 0.59 & EX 0.59 Lift TDC INT 0.192 & EX 0.179 (NO RETURNS)