if the header gasket is leaking due to a few bolts backing out , the gasket needs to be replaced. This just happened to me, I install the headers made sure all bolts were tight and a month or 2 later 1 day I started hearing an exhaust leak on the pass side of the engine. Put the car on the lift check all bolts on the exhaust, then saw a bolt backing out of the header. The header still leaks a bit because the gasket now has a hole in it from the heat. This happened in 5 miles of driving
1988 coupe race car 2700lbs 366rwhp
1965 2+2 fast back 4 speed tri power
1968 gt/cs 347 5 speed 380rwhp w/a E303 best cam ever!
1970 mach 1 428scj 4 speed v code 410 rwhp stock
1990 gt drag car 780hp on motor
1994 gt 320rwhp w/ ported gt40 heads, 1998 svt cobra
2003 svt cobra 456rwhp