Request Valve Spring pressure variables

Camshaft lobe profile, rocker ratio, component weight (valve spring, locks, retainers, valves) and RPM all play a role in picking a valve spring.

Typically valve spring pressure requirements are within a range (i.e 240-260 seat, 720-760 open) that will accomodate both intake and exhaust valves. This works well for engines with a Ti intake and a stainless exhaust valve because the valve weights are closer.

Another factor pertaining to consider is heat. This may be negligable with the spring alloys available to us.

I have a set of early -13 heads with Ti intake and exhaust valves that have different springs on the intake and exhaust valves. These heads were set up by an engine builder with at minimum 1000x morec insight on the subject that I do.

Lastly, a lot of the emphasis on not using too much spring is centered around wear and tear. Another aspect to consider in that equation is spring mass. A heavy tripple 1.625" OD spring might be better for longevity while a lighter 1.550" OD spring with a similar spring rate and IH, etc. might RPM higher due to less mass to control which generally equates to a more stable system. It's not uncommon for a 2.25-2.40" intake valve equipped engine to pick up 3-500 RPM by stabbing in a set of Ti valves.

The 511" in my GTS has 220 closed and 560 open with a .660ish net lift cam. Stainless 2.18/1.81 REV valves, Ti retainers and CM locks. It revs clean to 6800 and doesn't show and signs of the lifter roller wheels skidding. It peaked around 6100 on the dyno so I set the limiter at 6500 hoping for longer maintenance intervals.