I am trying to install new valve springs with the heads on the engine. I am using compressed air and one of the jaws type spring compressors with the knob on top to turn to compress the spring.

Problem is when I have the spring compressed the retainer and locks don't break free from the valve stem. I have tried tapping the top of the spring compressor with a dead blow hammer but that only worked to break free a couple of them. Do you guys have any other ideas for me? I really don't want to pull the heads.

By the way, these are BB eddy heads that are very clean so it isn't like things are shellac'd up.