All removable multi-piece exhaust collectors/stacks must be securely fastened with either: 1. NHRA-accepted header tether, or 2. A minimum ˝” (half-inch) weld located on each primary tube to the collector or 3. Be permanently attached to the vehicle body or frame with positive fasteners (i.e. exhaust hangers, support brackets, bolts/nuts, etc.) such that they require tools for removal.
A current list of NHRA-accepted header tethers is available on NHRARacer.com. Flexible tubing or “flex pipe” prohibited in all categories. If mufflers are used, they must be securely attached to exhaust system and car vehicle body or frame.
