Headers are from Doug's, and feature 1-3/4-inch primary pipe diameters. The headers carry P/N D-325, and were designed for popular '68-'72 Chevelles. The Engine Masters Challenge rules limit builders to headers designed for stock, unmodified chassis, so these same pipes will bolt into your Chevelle too. The long primary pipes (35 inches in length) will promote big torque numbers in the low rpm ranges, which will contribute to a higher overall score in the Challenge. The collector diameter is a street-sensible 3.250-inch.