first thing i would do would be to check to make sure that the compression gauge is working properly. bad compession like that if its not the valves i would start looking to see how well the rings are sealing. i wouldnt have taken the head off. put it back on make sure it is torqued right and i would do a cylinder leakage test on it. make sure that the piston of the cylinder that you are testing is at top dead center between compression and combustion(b/c between exaust and intake there is an overlap where both intake and exaust valves are open. pressureize the cylinder. check the exaust to see if air is coming out(theres a trick with a cigarette just stick it and if there is a leak from the exaust valve air will be coming out of the exaust pipe and it will be easier to see) if there is something wrong with the intake valves then air should come out of the intake(i guess that you could use that trick here too) but if the compression is going by the rings then it will come out of the oil filler cap. also check the head gasket while its off. if you're dogging you motor this could cause problems try to upgrade your internals to avoid problems. hope i was helpful. send me some feedback on what happens with this. oh and one other thing you could try adjusting your valves.