Headers EXTREMELY hot!

That may look like a dumb post topic, but just read this through:
I just put in a new camshaft. During the break in process, the header pipe turned flame read and caught the spark plug wire boot on fire.
I thought it was just touching, so I went out and wrapped the headers, new wires. And it did it again!
About after 7 minutes into the break in process.
And only on the one header pipe.
Plugs are gapped at .45 with MSD wires.
Car is a 72 chevelle with a SB 350.
Can I just installed is a comp cam with 218/218 @.50

Any ideas?

Thanks