Valve springs have 2 important pressure specs, seat pressure and open pressure. When buying valve springs, it is important to understand them both.
- Seat Pressure – The force holding the valves closed at zero lift.
- Open Pressure – The force pushing up on the valve at max lift.
How is it measured?
If you want to measure the pressure of your existing springs, use a Valve Spring Tester. There are a few styles available. Some can measure the spring while it is installed. Others require the spring to be removed from the engine.
The required spring pressure is based on the camshaft and lifters. The size of the valve also plays a part. (i.e. Big block engines need more spring pressure because the valves are bigger and heavier.)
Most cam manufacturers will list recommended valve springs. If not, follow the link below that matches your camshaft type:
How does it affect performance?
If the spring pressures are too low, a condition called “Valve Float” will occur.
- Follow this link to learn more about Valve Float.
If the spring pressures are too high, the added friction will result in:
- More heat,
- Faster valvetrain wear,
- Potential failure of other valvetrain parts (i.e. rocker arms, pushrods, etc.), and
- Less horsepower.