THE LONG AND THE SHORT OF FASTENERS

When Harley-Davidson brought out the new design known as the “Evolution” engine, a major goal was to eliminate oil leaks and gasket failures that had made the previous model the butt of light remarks. Earlier engines employed cylinders bolted to the crankcase by short bolts through a base flange. Heads were then bolted to the tops of the cylinders.

A major part of the “fix” was to replace the short base and head bolts with long through-studs that held down both cylinders and heads.

Why would this change keep engines leak-free? Think of bolts and studs as springs. When you tighten a bolt or the nut on a stud, you are stretching that bolt