Beginning at the K&N Filters Winternationals and continuing at the following two national events, the NHRA Technical department has studied the legality of certain small-block cylinder heads that have been used in NHRA competition within certain Comp-class combinations.

As part of this study, the NHRA Technical department visually inspected the General Motors small-block cylinder head on a group of vehicles that were competing in Econo Dragster, Econo Altered, and Super Modified, and then compared this information to the OEM head, part no. 234502615-X and cast no. 10134363. Based on these details, the NHRA Technical department has concluded that the cylinder heads found on certain vehicles do not meet the rules as stated in the rule amendment to the 2004 NHRA Rulebook.

In the CYLINDER HEAD section of each of the three classes, the following addition has been added, "Cylinder head must be commercially available over the counter from the OEM source and must conform to specifications as provided to NHRA by the OEM manufacturer. NHRA may use a cylinder head provided by the respective manufacturer to determine whether a cylinder head conforms to the specifications. … Any size valves permitted, valve guide angle must remain stock and valves must remain in stock location. Spark plug holes must remain in the approved location; angle milling permitted, provided all OEM parameters (i.e. spark plug location, valve angle) are unchanged."

Thus, the cylinder head that have were in question have been deemed illegal for NHRA competition within the Comp classes of Econo Dragster, Econo Altered, and Super Modified. This decision will be made effective April 1, 2004 for all cylinder heads that do not meet the stated requirements.