Actually, I'm running 20W50 as well. I was told by my machinist (who races many cars as well) that 20W50 is the oil he uses at all times. He said to run the motor at 2500rpm steady for 10-20 minutes if it doesn't overheat and then 1500-4000 up and down for 5 minutes. Then while its hot remove the valve covers re-torque the head bolts and set the lash to the proper specs. Cam specs say .022 for the lash. He said to set the lash at .026 or so until the initial break in period is over. Then drain the oil.