These are refurbished Power Bee 820 engine blocks. They have been NikaSeal plated and honed to the original diameter. These blocks have 3 or 4 bosses added for Prestolite and PVL ignition systems. They will work for 82007, 82031 and 82043 Rokon engines. They will also work for all 820 applications that use an adjustable stator plate type ignition system (points & electronic). Any stripped threads have been repaired with steel inserts. 4 of the intake ports have been Siamesed to help with flow. The exhaust ports were also opened up. Port timing was not changed. The bore for the clutch side seal has been grooved to accept an included snap ring to prevent seal blowouts. A riser is included to add a third mounting point for PVL ignition modules.There is a $25.00 core fee that will be refunded after your old block is returned.