Every DOHC Fiat crankshaft already has holes for dowel pins. These holes were probably drilled for locating and fixturing during the part's manufacture. Unfortunately for us, Fiat did not spend the money to also drill the flywheels to match. Dowel pinning is the process of doing just that. The major benefits of doing so are 1) the shear load of the flywheel bolts is greatly reduced, 2) pinning allows for precise alignment for balancing, and 3) the safety factor of the flywheel to crankshaft connection is enhanced.

The only materials you need are M10x20mm hardened and ground pins which are available from various vendors like McMaster Carr. The pin hole locations are available in the dimensions drawing in the gallery below.

In order to get a precise location, the original bolt holes must be located correctly. Once done, drilling and reaming for the pins is simple but should be done in a mill or drill press to make sure the holes and drilled perpendicular to the flywheel. Pins must be installed with a precise "slip" fit of 0.0005" or less.

Miller's Mule dowel pinning service: $30 (including pins)