As stated above, you have some stuck plungers. I just went through this in a 53 235. In most cases you can pull the lifter out and hit the top against an immovable object(I used my vice)and the plunger will move to the top. I would advise pulling the snap ring and completely disassemble the lifter and make sure it is free moving.
You may want to read about hydraulic lifters on my
BLOG. BTW, I use hydraulic lifters in every 235 I rebuild for customers with no problems. That is as long as the block is drilled to supply oil to them.
The key is to be sure air is not trapped in them.
