You want to press on the push rod side of the rocker arm. If you have hydralic lifters, the rocker will slowly go down to about 1/8" clearance on the valve stem. If you have mechanical lifters, you can push all day and should never get more then the hot or cold setting. It will take a little time to press the oil out, so press slow and steady and see what happens.
You can clamp vise grips on the rocker, or pry up on it, any thing you can do to force it slowly down. Joe
