Rocker, BBC & SBC Stud Girdles

Stud girdles increase rigidity by clamping around all of the rocker arm studs. This prevents them from independently bending and flexing from the stiffer springs and higher valve lifts found on high horsepower race engines. This improvement helps to prevent rocker arm studs from breaking under the increased pressure.

When rocker arm studs flex, the valvetrain geometry changes and the "effective" lift of the camshaft changes as the valves open at inconsistent distances as the engine revs. This results in a decrease in horsepower. By having stud girdles installed, strength is increased and the bending of rocker arms is drastically reduced. The improved consistency of valve opening results in an increase in horsepower when compared to an engine without stud girdles.

Understanding the answer to "what are stud girdles?" is relatively easy. A stud girdle is a solid bar that clamps the rocker arm studs together on a cylinder head to provide even load distribution across all of the studs and reduce flexing and bending which can cause them to break as well as horsepower loss.

A stud girdle is needed on high performance and racing engines with high-pressure valve springs and a high-lift camshaft. The increased force against the rocker arm studs will cause them to bend and flex. This causes variations in the distance a valve opens, affecting horsepower. If you don't have a stud girdle and you are experiencing damaged or broken rocker studs (after confirming everything is assembled correctly), a stud girdle may help.

When learning how to install a stud girdle SBC (as well as other engines), the best resource is the manufacturer's instructions as the installation process will vary. In most applications, the original rocker arm nuts that matched the rocker arms are not used. Stop clips from the stud girdle kit are installed on the end rocker arm studs to prevent the girdle bar from being too close to the rocker arms and making contact. Next, an extended-length polylock is installed on each stud. The rocker arms are then tightened down with these polylocks per the camshaft manufacturer's specifications. The lock / jam nut is then snugged inside the poly lock to prevent it from loosening. The stud girdle bar is then slid down the adjusting nuts until they reach the stop clips. At this time, confirm that there is no contact between the rocker arms and the stud girdle bar. The bolts that clamp the bars around the adjusting nuts are then tightened to specification. Next, double check the valve lash adjustment. If adjustment is needed, the bolts closest to the rocker arm need to be loosened to allow you to adjust the nuts. A common "best practice" is to re-check valve lash 3-5 times before constant running of the engine is performed to allow for the valvetrain components to properly adjust and settle together.

A JEGS expert is ready to answer your questions and help you find the rocker arm stud girdles that you need for your racing or high performance engine project.