Trying to do the cam break in on my rebuilt 289. It has a Edlebrock Performer Intake and a rebuilt 600 Holley carb and Pertronix Distributor otherwise stock. Cam/crank marks lined up with #1 up, Air mix is at 1 1/2 turns, total timing is at 34, intake re torqued after 10 minutes break in time, no vacuum leaks that I can find (all vacuum lines are plugged except the line from carb base to pvc), starts easily and sounds normal when running (which is why I don't see how I could be 180 off). The problem is that after a few minutes the headers get red hot and temp starts to rise. I've shut it down when it goes over 195. I've read that it's caused by timing being retarded, running too lean or rich or valves being too tight and exhaust valves not closing. (I checked with the engine builder and he assured me they were adjusted correctly). What am I missing? Thanks in advance for your help!