Checking cranking compression
Checking cranking compression can be a deceiving tool. The reason I say this is you don't know what sort of modifications to the cam have been done. A hipo cam generally will have a longer duration which means the valves are open longer. If the valves are open longer, you'll have less cranking compression.
Also, when performing a compression check, you have to make sure that the carb (throttle) butterflies are wide open. You can't suck in air past a closed throttle! Not keeping the throttle wide open will give an errant reading. Also, make sure that you have all of the other sparkplugs removed. You want to make sure that your battery is fully chargerd as well so the cranking speed is the same for all of your testing.
What a compression test will show you is the relational compression between all cylinders. You don't want to have any once cylinder off by more than 10-15% of the norm. If one or more cylinders are that much lower than the others, that would indicate a problem. You could have either a burnt valve, broken rings, a hole burned/cracked through a piston top, a blown head gasket, a 'torch hole' between two cylinders in the block itself (I have seen this in person, BTW), the list goes on, but you get the idea. If the low compression reading cylinders respond to a squirt of oil down the sparkplug hole by jumping back up to 'normal' on a retest, you have worn rings. If not, well, you'll have to tear the heads off to check.