I dont think you need 225 close pressure, I would look more on the 170lb closed, 450lb open. I know with a similiar or even less agressive cam and with 140 seat and 372 open the valves floated. In other words the lifter left the cam, hydraulic lifter did it job, took up the valve train slack pumped up. The problem is once the lifter contacts the cam again, the vavle train is out of "adjustment" and the valves hung open until the engine was shutdown and the lifters were left to bleed down and adjust properly. A hydraulic lifter under 60 psig of
oil pressure has a open FORCE of about 40 lbs, as you can see with spring pressure this is well below what it would take to open the valve but enough to take the slop out of the valve train. You may be asking why doesnt the lifter collapse when you apply 450 lbs of pressure, it is because when you try to push the lifter down a check vlv block
oil flow and it turns solid. Pretty darn nifty design!!!!!!