Crank stub PTO Viton Oring to prevent crank main seal blow out from wet sumping

Just slide this viton Oring on beside the crank main seal before you install the engine sprocket (chain or belt).  There should be nearly zero side clearance and that will prevent the main seal from inverting due to wet sumping (hydraulic force from too much oil in the sump).  This is the only real problem due to wet sumping and the Oring solves it.  Its cheap insurance and it beats oil shut off valves that can blow up your motor (see installed image).