I'm going to test some higher valve spring seat pressure on a pump gas blown 440 motor for a customer, I bought some Manley roller springs that have between 315 lbs. to 325 lbs. on the seats and between 640 to 675 lbs. opened at max lift.
I haven't verified the actual lift at the retainers yet with these springs as I am waiting on the new Manton Series 5 pushrods to get here, I'm relying on the cam card and advertised ratio on the Comp Cams stainless steel shaft rockers