In-cockpit view of Jeff Lavelle at the Reno Air Races in Heat #3A, He ran 399.420 MPH in the video. Earlier he qualified 403.059. The following year *shown below* - Lavelle shattered the qualifying and race records. 
Watch Jeff Lavelle's Ly-Con powered Glasair nearly lap the entire field in the 2014 Gold Final at the Reno Air Races.  Average speed for the 6 laps was 398.960 mph
A freshly overhauled O-320 gets run in the test cell.  
The same O-320 - View from the outside