Good Compression . . . Still Head Gasket?

I recently posted about blowing a lot of white smoke and got a lot of replies that it was head gasket. This morning I did a compression test and found that cyl 3 (one with the wet spark plug tip) was 120 while the rest are 150. According to manual thats still within acceptable range. It also stated 20% lower compression in one cyl could be a worn exaust lobe. And now it's not blowing any white smoke when warm or cold!? No oil in coolant, no coolant in oil, no power loss. Can a head gasket problem come and go or does this sound like anything else? Again, thanks for any info!

the exhaust lobe is the part of the cam that pushes open the valve.

sometimes you won't get any oil in the water, or water in the oil. With th compression being that far off in that cylinder it could be in acceptable range bythe manual fr a older engine with some wear. I would check valve seal and guide it sounds like you have a valve that isn't sealing or the smoke you see might be oil getting into the piston and burning off. i would check that and the head gasket. i remember you saying the motor was new go to who installed it might have a warranty but if you pull it apart it might void it. good luck