Any broken rings? I took apart a 340 I bought and found all 8 pistons had the top ring broken and one piston with the second ring also broken. No wonder why that engine was parked.
I can't answer your cam question, but there are many things that can negatively affect performance. For example: improperly degreed cam, too much ring gap, timing way off, etc.. Did the person who worked on the engine know what they were doing?
