If you are running over 4,500 rpm with a high lift cam, we suggest going with our 135lb valve springs with different heat treat and shot peen, for better longevity in extreme applications, as well as our light-weight 4130 or titanium retainers. We also recommend this if you are running larger valves. We set the install height higher so that they can handle a higher lift cam and more boost pressure.
This also has a 1.45-1.5 installed height. We have longer valves to accommodate this installed height, if necessary.