When I had my 350 CID Olds in my '70 Cutlass rebuilt for drag racing I brought it to the dyno after about 450 miles. Each run increased the horsepower and torque significantly. The way it was explained to me was that the rings were sealing with the WOT runs at high RPM on the dyno. Of course after the third run my head gaskets blew because it got to hot and the car was never the same again 
Jeff Sherwin
Jeff Sherwin
