Hi, I purchased a 1969 mustang grande with the 250 inline 6 motor. everytime I start it the carb catches on fire, the firing order is in the right postion and i have adjusted the timing of the distributor in every way imaginable to try and get it to stop. The Valves were done and adjusted and the head was surfaced there where no cracks in it. The headgasket was also changed when this was done and the Carb was also rebuilt. any suggestions? Thank You in advance