Maximum rated horsepower allowed in factory stock cars

[SSDiv6]

NHRA does not have the authority to change or override an SFI chassis specification. SFI is an independent motorsports industry entity that serves all types of motorsports, not only in the USA but also worldwide. Doing so puts a liability on NHRA in the event of a crash.

The current applicable specs are as follows:

SFI Spec 25.3C: Full Bodied Car with Aftermarket Body Shell and Tube Frame, OEM Body Shell and OEM Frame with OEM or Modified Floorpan and Firewall, or Uni-Body with OEM or
Modified Floorpan and Firewall Roll Cage – 6.50 to 7.49 Seconds ET;
3,600 lbs. Maximum

SFI Spec 25.5D: Full Bodied Car Stock or Modified/OEM Floorpan and Firewall with OEM Frame or Uni-Body Construction – 7.50 to 8.49 Seconds;
3,600 lbs. Maximum

SFI Spec 25.6: Full Bodied Car Stock / Truck or Modified/OEM Floorpan and Firewall with OEM Frame or Uni-Body Construction – 7.99 to 8.49 Seconds;
5,000 lbs. Maximum

SFI 25.3C and 25.5D is limited to 3,600 lbs. maximum.
Although SFI 25.6 allows up to 5,000 maximum, is limited to a 7.99 ET.

[Coleydog]

Interesting how the SFI got those numbers? Did they take a 3000, 3600 and a 4000 lb car, wreck them, then see how they faired? I know there's math involved, but in my opinion, way to many variables unless there's one cage fits all. If pushing the limit of 1-5/8" cm, go to 2", more than doubles the strength. There are ways around this dilemma, look at NASCAR. Over 4000lbs and those cars hit a few walls time to time. Amazing when you're been at the top for a long time, after awhile questions don't get asked.
Like I said, my opinion, Mike

[SSDiv6]

Originally Posted by Coleydog

Interesting how the SFI got those numbers? Did they take a 3000, 3600 and a 4000 lb car, wreck them, then see how they faired? I know there's math involved, but in my opinion, way to many variables unless there's one cage fits all. If pushing the limit of 1-5/8" cm, go to 2", more than doubles the strength. There are ways around this dilemma, look at NASCAR. Over 4000lbs and those cars hit a few walls time to time. Amazing when you're been at the top for a long time, after awhile questions don't get asked.
Like I said, my opinion, Mike

SFI uses actual crash data and analysis to come up with the specification. In addition, many of the top chassis builders are also consulted.
It is not an arbitrary number.

[trode424]

I know this is a old thread, but has anyone got any clarification on this? Thanks, Todd

[SSDiv6]

Originally Posted by trode424

I know this is a old thread, but has anyone got any clarification on this? Thanks, Todd

Nothing has changed.
This is the only SFI Guidance applicable to drag racing stock body cars:

SFI Spec 25.5D - Full Bodied Car Stock or Modified/OEM Floor Pan and Firewall with OEM Frame or Uni-Body Construction
– 7.50 to 8.49 Seconds; 3,600 lbs. Maximum
Effective Date: May 5, 2018

SFI Spec 25.6 - Full Bodied Car Stock / Truck or Modified/OEM Floor Pan and Firewall with OEM Frame or Uni-Body Construction
– 7.99 to 8.49 Seconds; 5,000 lbs. Maximum
Effective Date: August 26, 2016

[trode424]

Originally Posted by SSDiv6

Nothing has changed.
This is the only SFI Guidance applicable to drag racing stock body cars:

SFI Spec 25.5D - Full Bodied Car Stock or Modified/OEM Floor Pan and Firewall with OEM Frame or Uni-Body Construction
– 7.50 to 8.49 Seconds; 3,600 lbs. Maximum
Effective Date: May 5, 2018

SFI Spec 25.6 - Full Bodied Car Stock / Truck or Modified/OEM Floor Pan and Firewall with OEM Frame or Uni-Body Construction
– 7.99 to 8.49 Seconds; 5,000 lbs. Maximum
Effective Date: August 26, 2016

Does 3600 include driver? Ive seen plenty of 2018 and up copo's and cobra jets running FS/AA .

[bsimms89]

Originally Posted by SSDiv6

NHRA does not have the authority to change or override an SFI chassis specification. SFI is an independent motorsports industry entity that serves all types of motorsports, not only in the USA but also worldwide. Doing so puts a liability on NHRA in the event of a crash.

The current applicable specs are as follows:

SFI Spec 25.3C: Full Bodied Car with Aftermarket Body Shell and Tube Frame, OEM Body Shell and OEM Frame with OEM or Modified Floorpan and Firewall, or Uni-Body with OEM or
Modified Floorpan and Firewall Roll Cage – 6.50 to 7.49 Seconds ET;
3,600 lbs. Maximum

SFI Spec 25.5D: Full Bodied Car Stock or Modified/OEM Floorpan and Firewall with OEM Frame or Uni-Body Construction – 7.50 to 8.49 Seconds;
3,600 lbs. Maximum

SFI Spec 25.6: Full Bodied Car Stock / Truck or Modified/OEM Floorpan and Firewall with OEM Frame or Uni-Body Construction – 7.99 to 8.49 Seconds;
5,000 lbs. Maximum

SFI 25.3C and 25.5D is limited to 3,600 lbs. maximum.
Although SFI 25.6 allows up to 5,000 maximum, is limited to a 7.99 ET.

I see what you say about the 25.6 being good up to 5,000lbs but only 7.99ET, but in the rule book NHRA says stock cars running faster than
8.50 must have an SFI 25.4 or SFI 25.5 cage, no mention of 25.6, and these cars are becoming capable of 7.99

[SSDiv6]

Originally Posted by bsimms89

I see what you say about the 25.6 being good up to 5,000lbs but only 7.99ET, but in the rule book NHRA says stock cars running faster than
8.50 must have an SFI 25.4 or SFI 25.5 cage, no mention of 25.6, and these cars are becoming capable of 7.99

NHRA can opt the use of the SFI 25.6 for the Hellcat and hope they don't go faster than 7.99