i have an 03 cavalier with an ld9 swap (i bought it like that the guy blew the eco and swapped in a spare ld9 he had) i fixed the threads were the cam towers bolt on to so after its all fixed i start it up look for leaks luckily there are none so rev the engine a bit 1/2 throttle then 3/4 throttle then WOT and one of the lines in the back that goes through the fire wall (it has some heat wrap and a small vent like looking thing) Catches FIRE i have no idea why its the second time it does that anyone had that problem before? is my header getting to hot? are the fumes comming aout of that "VENT" FLAMMABLE? can some one help me?

Same or similar thing happened in my old 96 Z24.... a few years back. Suddenly there was smoke coming from somewhere in the engine bay, I stopped the car and ran to the sidewalk on the other side of the street waiting for an explosion "movie style" of the car, then my business partner who ran with me ask me for a fire extinguisher and I remembered I had one in the trunk so we sprayed the back of the engine with it and we did not have any explosion... replaced the heater core hoses (H shape hoses) being very careful to place them as far from the header as possible and problem solved it never happened again. If the hoses are too close you could use tie straps to keep them away from the header also get good fire and heat resistant covers for the hoses just in case.

well it hasnt caught on fire again i put heat wrap on it and tie straps and havent seen any smoke or fire im thinking of just connecting a "U" on them and delete the heater core im from the valley and dont need it its always hot here lol