The following Stock/Super Stock horsepower changes were released December 7, 2022 produced by the Automatic Horsepower Factoring System (AHFS). This is the scheduled horsepower adjustment for this year. All changes are effective January 1, 2023. 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 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 two-time a year process when a 1.20 and under run is recorded during any NHRA event.
Any comments, thoughts, or requests must be sent in writing to: National Hot Rod Association; Technical Department; attn: AHFS; P.O. Box 5555, Glendora, CA 91740; or e-mail, AHFS@nhra.com or pcvengros@nhra.com
Stock Horsepower Changes
Engine OEM NHRA New
Make CID HP HP HP Years Affected
Chev 327 275 278 282 67-68
Chev 350 180-185 279 283 77-78
Chev 350 360 325 330 1970
Chev 376 365 365 370 2015
Chev 350 590 630 638 17-18
Chev 350 600 600 614 19-22
Mopar 340 290 304 311 1970
Mopar 383 330 294 300 1969
Mopar 360 245 310 317 1974
Dodge 370 340 399 404 09-10
Dodge 392 380 402 408 11-13
Mopar 426 365 291 295 1964
Ford 302 140 143 147 1979
Ford 302 140 151 153 1974
Ford 302 325 325 333 2012
Ford 330 450 570 578 2012
Ford 330 510 534 547 2012
Note: See class guide for specific details
Super Stock Horsepower Changes
Engine OEM NHRA
Make CID HP HP New HP Years Affected
GM 307 140-155 220-223 229 80-88
Chev 572 500 500 512 2022
Dodge 354 530 537 550 2015
Ford 302 560 560 567 2014
GM 305 190-230 243 249 88-92 GT
GM 305 210-230 258 264 88-92 GT
GM 350 225-230 284 288 88-89 GT
GM 350 240-245 282 288 90-92 GT
GM 350 240-245 293 297 90-92 GT
GM 350 250 284 288 90-91 GT
Ford 330 435 471 477 2010 FGT
Ford 351 275 313 317 1972 GT
Pont 428 375 330 335 1968 GT
Pont 428 390 335 343 1968 GT
Note: See class guide for specific details
Class Index Changes
Class Current Index Changes New Index
SS/VX 11.45 -.05 11.40