I built a customer a new motor last summer,new World block, Mopar iron heads using a Comp Cams huydraulic roller cam and lifters and . I set the spring pressures at 175 lbs. or so on the seats and 375 to 390 over the nose. That was using Comp Springs, 10 degree retainers and keepers. Those pressures are the max that Comp said to run them at