NHRA Technical Department Makes Changes to the FLEXJET NHRA Factory Stock Showdown
- Apr 24
- 2 min read
Beginning May 1st, 2026, FLEXJET NHRA Factory Stock Showdown competitors may use ported supercharger cases. NHRA reserves the right in the future to make additional rule changes to control performance and maintain parity in the category.
2017-2018 Camaro COPO 350
• 590 HP Supercharged 2.9L Whipple
• Upper supercharger pulley (3.125) inches
• Lower engine pulley (8.000) inches
• Overdrive ratio 2.560
2019, 2020, 2022-2023 Camaro COPO 350
• 630 HP Supercharged 2.65L Magnuson
• Upper supercharger pulley size: (3.500 3.625) inches
• Supercharger rear jack shaft cog pulley 34 teeth
• Supercharger rear cog pulley 32 teeth
• Lower engine pulley (8.000) inches
• Overdrive ratio 2.429 2.345
2015 Challenger Drag Pak 354
• 540 HP Supercharged 2.9L Whipple
• Upper supercharger pulley size: (3.000) inches
2021 Challenger Drag Pak 354
• 630 HP Supercharged 3.0L Whipple
• Upper supercharger pulley size: (3.625 3.750) inches
• Lower engine pulley (8.000) inches
• Overdrive ratio 2.207 2.133
2010 Mustang Cobra Jet 330
• 435 HP Supercharged 2.3L Eaton
2012 Mustang Cobra Jet 330
• 450 HP Supercharged 2.3L Eaton
2016 Mustang Cobra Jet 302
• 575 HP Supercharged 2.9L Whipple
2019 Mustang Cobra Jet 327
• 610 HP Supercharged 3.0L Whipple
• Upper supercharger pulley size: (3.625 3.750) inches
• Upper supercharger pulley size with iron block:
(3.625 3.750) inches
• Lower engine pulley 6.938 inches
• Overdrive ratio aluminum block 1.914 1.850
• Overdrive ratio iron block 1.914 1.850
2019 Mustang Cobra Jet 351
• 570 HP Supercharged 2.9L Whipple
• Upper supercharger pulley size: (3.500) inches
SUPERCHARGER
Must be correct year, make and model specified & accepted for cars engine. Blueprinting permitted per NHRA Specifications available from NHRA Technical Services Department. Supercharger case and rotors may be coated. Supercharger case may be ported. Rotor assembly must remain OEM length, helix and diameter as accepted by NHRA. Modifications to rotor prohibited. Coating of rotor permitted. Any supercharger drive system must remain as NHRA accepted and unaltered.
SUPERCHARGERS/INTAKE MANIFOLD/INTERCOOLER
Must be correct unaltered OEM manifold consistent with year, make and model specified for cars engine. Sandblasting, grinding, flash removal, dry film coating, or any other modification to supercharger, intake manifold, or Intercooler prohibited. Intercooler must remain in OEM, NHRA accepted location.
