40-300 hrs. it really depends on who built it,how you run/maintain it etc.etc. my 600+horse n/a engine was running awsesome at 300+hours when i pulled it out. my blower engine i got rid of after 40hrs and is still very strong. but i change the oil every 10hrs or after it smelled bad whichever came first. if you still havent built it go with a very reputible builder no matter the cost. try larry's engines in tucson az.lot's of my buddies use him and i've never pulled them back with a broke engine.