Depending on where the valves were when you shot air into the cylinder it would put air in the crankcase as you have oil holes in the head.Is it a used engine? Also local auto parts store or Napa sell a kit that has different threads for an automotive compression gauge-I haven't bought one yet because it's like $60.This may sound funny but when I put my finger over the plug hole and pushes my finger away easily it's usually about 120+ psi !!!If it doesn't have enough compression to push my finger away it's 60psi or less.
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