alright fellows i've just done some mods to my 454,got problems.this is a stock bore 454,i put some later model sqaure port heads on itwith new stainless valves matching valve springs and liftersa 268 voodoo cam ,a mallory 5500 rpm hei coil,and put an GM factory alum. intake,which by the way is a marine intake, and a 850 holley which was used when I got it have no history on it.I've got this in my 72 chevelle,just fired it up last night idled it up to break in the cam let this thing run for about 3 min. the headers are cherry red shut it down quickly, WHATS GOING ON