July 18, 2025

The Tech Department has issued a list of frequently asked questions and answers on the subject of modifications in SS/AH. As with any category, racers in SS/AH are constantly looking at smaller and smaller details in their quest for performance, necessitating periodic clarifications or interpretations of the text contained in the NHRA Rulebook. Input from NHRA Technical Inspectors, engine builders, competitors and manufacturers was used to determine the correct and current answers to these frequently asked questions, and to better clarify NHRA’s position on what is and what is not acceptable. The following information pertains to SS/AH ONLY. For questions and answers on other classes or categories, consult the 2025 NHRA Rulebook or contact NHRA Technical Services headquarters.

1. Can I have Removable or modified inner fenders? NO

The 2025 Rulebook states: "Alteration to shock or spring towers prohibited."

In order to maintain a stock appearance, the entire shock tower and inner fender panel area may not be modified with bubbles, dimples, humps, bumps, lumps, or tubs. Also, cutting, moving, and refinishing inner fender panel surfaces not allowed, even if it "looks stock."

 2. Can I use velocity stacks? NO

Ram tubes and/or velocity stacks prohibited. 

3.  Can I use oversized air pans with a ramp/diverter? NO

SS/AH may use an insert to enclose carburetors. The insert must be flat and

level with OEM hood surface. Ramps, diverters or other devices that may affect airflow, are prohibited.

4.  Can the carburetor orientation be reversed? NO

Mounting carburetor backwards or sideways is prohibited.

On multiple carb applications, carbs must retain “original relationship”.

Since the OEM relationship was a cross-ram, the carbs must remain staggered on opposite sides of the manifold. The position of cross-ram carbs may be altered from front to rear (example: if OEM configuration has the left carb placed ahead of the right, relationship may be reversed so that left carb is in back with right in front) – use throttle bore centerlines as determining factor. Choke flanges must face inboard.

5. Are titanium valves permitted? NO

Any aftermarket steel valve permitted; must maintain stock head and stem size; titanium valves prohibited.