so i desided to do a compression test on my 4.6L in my auto class and i got some puzzling results. presuming cylinder #1 is on the passenger side, cylinders 1-4 showed and average compression of 145 psi, normal. so i start testing the drivers side, thats when it gets weird, the cylinders would work there way up to 145 psi, but when i stopped cranking the psi would drop to zero. my car has never had a misfire problem ever. i even tried another tester with the same results.my instructor said it may be a blown head gasket. so any thoughts.