Inliners International Forums General Discussion Hi Performance valve tapping sound on 292

twisted, its a crower stage 3 hyd cam (262, the gear was heated when we put it on, the rockers have plenty of oil none are on the dry the side, today I was listening to it as it ran and I tried to take off oil fill cap and there was so much vacuum I couldnt get the cap off until I shut the motor off, never had a motor do that before,