No Compression

I added a dose of 100psi to all the cylinders and air was blowing out the carb on all of them. So i tap the valves with a rubber hammer to see if they were stuck they moved and still continued to blow air out of the carb on all cylinders. No air at all out the exhaust. So your right guys...not the head gasket. So what would cause all the intake valves not to seat properly. Maybe the previous owner never adjusted them I guess. But I would think that it had to be getting some compression when parked 13 years ago.