The following Stock/Super Stock horsepower changes were released December 22, 2017 produced by the Automatic Horsepower Factoring System (AHFS). This is the second of two scheduled horsepower adjustments for this year. All changes are effective January 1, 2018. 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
Complete for 2nd half rating period of 2017
Engine OEM NHRA New
Make CID HP HP HP Years Affected
Chev 327 250 251 255 1965 Impala
Chev 350 350 372 377 13-15 COPO
Chev 427 425 467 473 12-13 COPO
Chev 427 450 472 483 14-15 COPO
Chry 146 180 209 214 2004 PT Cruiser
Mopar 273 180 171 174 65-67 Belvedere
Dodge 345 305 342 347 09-10 Drag Pak
Dodge 426 450 490 497 09-10 Drag Pak
Ford 302 139 139 141 1978 Fairmaont
Ford 302 350 363 372 2014 Cobra Jet
Ford 302 350 383 388 2013 Cobra Jet
Ford 302 525 563 571 2014 Cobra Jet
Ford 302 565 565 573 2016 Cobra Jet
Ford 330 435 504 516 2010 Cobra Jet
Ford 352 285 361 370 2010 Cobra Jet
Olds 350 200 254 258 1972 Cutlass
Super Stock Horsepower Changes
Complete for 2nd half rating period of 2017
Engine OEM NHRA
Make CID HP HP New HP Years Affected
GM 305 150-200 259 263 83-87 Camaro/Firebird
Chev 350 530 583 597 14-15 COPO
Dodge 345 305 312 320 09-10 Drag Pak
Dodge 426 450 462 468 09-10 Drag Pak
Ford 302 575 575 583 2016 Cobra Jet
Ford 330 435 528 540 2010 Cobra Jet
Ford 352 285 285 289 2010 Cobra Jet
Pont 400 200 285 290 1974 GT/RWD*
*= correction to match 1974 400 225/290
