One Glowing Header Tube???

[70TWO NOVA]

Hey guys,
Here is the situation; I just built a brand new engine (sbc 355) for the Nova. Went to break it in and after about 5 minutes of running it at around 2500rpm to break in the cam i notice that the header tube on cylinder #5 is glowing red hot. None of the other cylinders are glowing. What could cause this on only one cylinder? Also i noticed some white residue inside the tube when i removed the header. Any help is greatly appreciated.
Thanks,
Brian

[Vegas69]

Lean condition on that cylinder. What does the plug look like? Check for a vacuum leak at that intake runner.

[chevyIIpost]

I would check the exhaust valve adjustment also and look for a tight exhaust valve.

[70TWO NOVA]

thanks, will do