MED ROAD VALVE SPRINGS

Firmer valve springs improve valve control and reduce float (valve bounce) at higher RPM levels, improving performance and reducing the chance of valvetrain failure. By using a pair of springs, load is spread across a wider contact patch. Using two springs also reduces the chance of catastrophic engine damage when a single spring setup fails.

This is the force exerted by the springs to the valve spring seat platforms when compressed by the stem top caps on the cylinder head. The 70lb seat pressure figure shows the force at the recommended fitted length, when the valves are fully closed. The 170lb seat pressure figure presumes an additional 0.475" of compression by the rockers, via the cam and pushrods.

Install your valves, collets and top cap without the springs fitted. With the valve fully closed, take a measurement from the underside of the valve cap to the spring seat platform. For optimum performance, this 'gap' should measure 1.380" on every valve. Use our valve spring seat shims to reduce the gap, machine the valve spring seat platforms or valve seats to increase it.

This figure is only achieved at 0.475" valve lift. More mild engine builds will not see this much valve lift, so the maximum spring pressure will be lower. For example, the MED HT will only give 0.358" maximum valve lift with standard rockers. By comparison, the most aggressive road cam in our range, the XT, will give 0.470" valve lift with 1.5:1 rockers. So the maximum spring pressure is also denoted by the camshaft and rockers.

We would usually change them during an engine rebuild, as like any steel spring, they will weaken off over time with use. You will need a valve spring pressure tester to check condition, which is quite a specialist piece of kit, so as a general rule, change during a rebuild for peace of mind.

No - standard types, MED steel or titanium all work well.