I will be breaking in a new cam (292\ .501) so I am trying to remove the inner valve spring per recommendation. So I bought the air hose that screws into the spark plug hole, and the proform rocker shaft mounted valve spring compressor for small block mopars. My air compressor pumps the cylinder up to about 80-90 psi and the valve spring compressor tool is easy to use. My problem is when I compress the spring the valve goes down with it and blows highly compressed air out the intake/exhaust port. How much psi do you need to hold the valve stem in place? 90 is the max my air compressor goes up to. I would think 80-90 psi would be enough. Is there something I am missing? Any other way to hold the valve stem in place when I compress the spring down. I really don't want to take the heads off to remove them. 340 with x heads.