Q: In 2004, I bought a Lycoming O-320 D1A, via Van’s, and started flying it in January 2005 in a RV-9A. I broke it in according to the instructions (75% or more until oil consumption stabilized). In spite of having an oil filter I always do oil changes at about 30 hour intervals. All through the life of the engine it has used 100LL and the average power (after break in) can be estimated from the fuel consumptions of 5.9 to 6.1 max gph. Cylinder head temperatures during takeoff remain below 400°F on a calibrated (boiling water) steam gauge and at about 350°F in cruise.
In April 2010, at 676 hours, I had a sticking valve. Curiously this manifested itself not at cold start-up but during takeoff.