hissing sound when turning crankshaft manually

[spyghost]

hi,

is it normal to hear hissing sound when turning the crankshaft manually with the valve cover opened? i was adjusting tappet clearance when i noticed that there was hissing sound when turning the crankshaft, i just can't pinpoint where it comes from

[jvnj]

Chief, hissing sound is the compressed air within the combustion chamber being slowly released. Yes, its normal . Thanks

[speedyfix]

if the plugs were still installed it's normal. kung nakatangal dapat wala ka marinig.