red hot

Just started a re-built 460 to break it in but 10 minutes later had to shut it down because the headers got red . Any idea what the reason might be  

Timing, fuel or both. Double check the tune up.....
You will find it.
Keith

X2,timing is probably slow and/or lean tuneup.

X2 ^^^^

not enough timming, retarded so slow late burn.