I'm trying to do the cam break in on my rebuilt 289. It has an Edlebrock Performer intake, a rebuilt 600 Holley carb and Pertronix distributor otherwise stock. Cam/crank marks lined up with #1 up on compression stroke, air mix is at baseline-1 1/2 turns and it has 66 jets, total timing is at 34 per timing light, intake was re-torqued after 10 minutes break in time, no vacuum leaks that I can find (all vacuum lines except the line from carb base to pvc), starts easily and sounds normal when running. The problem is that after a few minutes the headers are glowing (pic attached-530 per laser heat gun). After 5 minutes it gets to 210 and I shut it down (I have 2 box fans in front of the radiator). I'm also attaching a pic of the cooling system while running (belt is tight, etc.). I know often headers will glow red during break in and some mfrs will recommend not putting on headers until after break in but as you can see in the pic and noted above, they're getting really hot. I also know that one of the things that can cause this is the timing being retarded. Per the timing light I don't think this is my problem. I also know that it can be caused by valves being too tight but my engine rebuilder assures me they were adjusted correctly. I also know it could be caused by the carb being too lean or too rich but I don't think that's it either. I'm at 15 minutes accumulated time in 3 attempts. What am I missing??? Thanks in advance for your help.
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