Understanding Valve Springs

            One of the most common questions we get here at Jegs is “Why do I need to change my valve springs if I am upgrading my camshaft?” Valve springs are one of the most critical components of an engine and also the most overlooked. Simply said, valve springs control an engines mechanical RPM capability.

            If I purchase a camshaft that raises my engines powerband from a maximum RPM of 5800 to 6500 and don’t change my valve springs my engines maximum powerband RPM is still 5800.

            Valve springs need to be matched to the camshaft and all camshaft manufacturers have the recommended springs for all of their camshafts. If the duration number of a camshaft goes up so does the RPM capability of the engine, so the spring pressure must be increased also.

            You will see some terms associated with valve springs such as O.D and I.D and of course those are outside and inside diameter and those will change with the type of cylinder head we are using. There are single, double, and even triple springs. Again the higher the RPM the more spring pressure needed, so a single spring for lower RPM engines up to a triple spring for higher RPM engines. Open and closed pressure and installed height are the most crucial terms when it comes to valve springs. Open and closed pressure is determined by the cam we have chosen and installed height ensures that we have the correct pressure once the spring is installed.

            When we see on our camshaft and valve spring paperwork that the springs must be installed at 115lbs@1.900 it means the spring must exert 115 pounds of pressure when compressed to 1.900”. So the distance between the bottom of the valve spring retainer to the pocket in the cylinder head must be 1.900”.

            So as you can see to get the full potential of our new camshaft we need to change the valve springs, it is not only a lot of work to change the camshaft in our engine but it is also a major investment. So why not spend a little more time and a little more money to get the power we are looking for.