Ferrydude is quite correct, and TCM has loads of data on the subject for confirmation.
Likewise Pratt&Whitney with larger radial engines.
UAL was authorized to operate their R2800CB16 engines (installed on DC-6B's) to 3,300 hours until overhaul, and when one of these engines was sent to P&W for analysis, it was put on a dyno and checked for power output, the results surprised no one...yes, specific BHP was reduced, but only by three percent, and this was in the dry takeoff mode, wet takeoff, two percent.