Sons 300m and I need help please!

First I pulled the timing cover back off to check my marks, they were good. Then I did a compression and spark test after.
Motor still turns over fine.
Low cylinder is 150 high was 160 dry.
All cylinders jumped spark great at .065".
Also, rocker arm crossed my mind along with spring.
Motor is a 4 valve (2 in and 2 ex)
One of the springs or rockers could be broke and still get good compression I think.
Anyone have any thoughts on my logic? or lack of?