When using the pressure tester,...
When using the pressure tester, simply check to see how much pressure is required to move the valve off the seat and log your results.
Performing a quick check of your valvespring pressures is a simple and easy procedure. The good news is-if you aren't doing it already-checking your spring pressures weekly (or at least after every other race) adds only a few minutes to your total maintenance schedule and greatly reduces your chances of a blown engine.
No matter the manufacturer, valvesprings almost always display the same pattern over their working life. During break-in the springs will usually lose a few pounds of pressure then level off. They will stay at that pressure until just before they reach the breaking point from wear. So by tracking how the springs are holding up you can catch a failure before it happens and avoid a broken valve, which often leads to all sorts of other bad stuff.
A valvespring seat pressure...
A valvespring seat pressure tester is practically the only tool necessary to monitor your springs for signs of failure.
To keep a check on spring pressures, you will need a reliable valvespring pressure checker. An on-head checker means you only need to remove the valve covers to perform your check. Race engine specialist Ken Troutman of KT Engine Development has used this Moroso unit for years, and it's still available from Moroso in an improved form.
Check your valvesprings when the engine is new and log the pressures. You may notice the spring pressure drops a little bit after the first couple of races-especially if the engine hasn't already been broken in on a dyno-but it shouldn't be too much and it should level out. Then, if you notice a drop again you will know it is time to swap out to a new set. A good sign is a drop in pressure of 10 percent or more. If you see the drop in a single spring, you may be able to get away with swapping out that valvespring, but if it happens to two or more springs at once it's a sign that the set has reached the end of its useful life and should be replaced.
Biting the bullet on the cost of a new set of valvesprings can be tough when your race engine still seems to be working perfectly well, but saving yourself the headaches of repairing-or replacing-a blown engine is well worth it.