"Back fire" refers to fire coming back into the induction system, which may indicate a lean condition.
Tommy,
My friend's 347 has a temp of around 650deg at idle at the collectors, 900 or so under normal load.
Gents,
Take a look at Earl's Performance Pluming's "Pressuremaster" header gaskets. Summit p/n EAR-29D03A. They have worked well on his Cobra.
Steven
