The following Stock/Super Stock horsepower changes were released December 9, 2025 produced by the Automatic Horsepower Factoring System (AHFS). This is the scheduled horsepower adjustment for this year. All changes are effective January 1, 2026. It should be noted that these changes include only results produced by the AHFS, and do not include written letters or requests. Those changes are listed separately.

        The AHFS is a program based on actual run data compiled from all available runs at NHRA national and divisional events. The data-based format provides the ability to calculate average performances for any class and/or engine combination in Stock and Super Stock. The trigger point for the system is 1.00-second or more under the respective index, and must be produced on two different occasions. Engine-combination averages and class averages are then computed and analyzed to determine if a change is warranted. The amount of change is calculated on a stepped percentage basis. Where applicable, adjustments will be effective for the specific car model or body style being evaluated. An automatic adjustment is instituted outside the one-time a year process when a 1.30 and under run is recorded during any NHRA event. Any comments, thoughts, or requests must be sent to: AHFS@nhra.com or pcvengros@nhra.com

Stock Horsepower Changes

Engine                   OEM          NHRA      New

Make          CID     HP            HP           HP           Years Affected

AMC            258      150           148        150                  1977

Chev           283      220           214        219                   65-66

Chev           283      220           226          229                 64-66

Chev           305      160           190          197                 1986

Chev           307      various      160          164                 71-72

Chev           327      275           282          289                 67-68

Chev           350      190           285          292                 1981

Chev           350      180           275          279                 1980

Chev           350      350           358          370                 13-15

Chev           350      350           419          425                 13-15

Chev           396      390           428          442                 13-15

Chev           454      425           420          426                 1971

Mopar          273      180           166-174  177                  65-67

Mopar          426      365           296          300                 64-65

Ford            302      225           220          223                  1992

Ford            390      320           327          332                  1967

Note: See class guide for specific details. Updates highlighted in Yellow

Super Stock Horsepower Changes

Engine                   OEM          NHRA     

Make          CID     HP            HP           New HP  Years Affected

Cadi            350      170           203          206                 1978  GT/RWD

Cadi            350      170           203          209                 1978  GT/FWD

GM              350      225-230    296          303                 88-89 GT/FWD

GM              350      275-300    306          310                 92-98 GT/FWD

Mopar          354      530           570          583                 2015

Mopar          426      425           500          512                 64-65

Ford            429      455           477          483                 2014

Pont            428      375           343          351                 1968 GT/FWD

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