Rebuild frequency is entirely up the owner. The engines are very reliable and owners typically rebuild engines due to a small drop-off in power rather than for reliability. Most racers will only rebuild an engine once at the beginning of the season if only competing in a 6-round state series. Serious competitors who race more often and want maximum power will typically rebuild the engine at the beginning of the season, then once mid-season as well. A standard 'freshen-up' rebuild could cost anything between $800 and $1500 depending on what work needs to be done, and whether a dyno run is included or not.