[BRENT in 10-uh-C]

A stock flywheel with a reproduction ring gear is actually installed with a 0.0015" interference fit. The ring gear is heated and then slipped onto the flywheel so that when it cools, it will shrink to fit tightly.

If you find yourself with an issue of a ring gear trying to slip on a flywheel, here is a trick that you can do. I install electric starters on early brass-era stuff that did not come with an electric starter. I make the flywheel ring gears for these engines and mount them onto flywheels (that never had an electric starter nor a provision for a ring gear). On those, I roll the ring and then weld it together. Then I slip the ring gear over the flywheel and drill down into the ring gear and the flywheel at the same time. One half of the diameter of the drill bit is drilling into the flywheel and the other half is drilling into the ring gear. I drill these holes 90° apart and thread them to install ¼-28 set screws. These act as a sprag to keep the ring gear from rotating on the flywheel.