Cylinder hold down nuts are an effective way to keep the cylinders in place when the heads are removed from the engine. This is particularly useful when installing the second cylinder over the piston and rings after the first cylinder has been installed. It is also advantageous to have the cylinders secured when rotating the crankshaft for other work. In any case, even a slight rocking of the cylinder can damage the base gasket or cause a cylinder to lift entirely off the cases. These new JIMS® Hold Down Nuts have different threads at each end. One end fits Twin Cam® models, while the other end works with M8 engines.