The NHRA has recently announced a new class featuring doorslammer vehicles for the 2022 season. Known as NHRA Factory X (short for Factory Experimental) or FX, it is effectively a combination of Pro Stock (PS) and Factory Stock Showdown (FSS) vehicles.
The class will be reserved for cars manufactured in 2019 or later, primarily the Chevrolet COPO Camaro, Dodge Challenger Drag Pak and the Ford Mustang Cobra Jet.
Tim Essick’s Mustang, which he runs in the PDRA, has exactly the same external look as that of the Factory X cars (Courtesy of Tara Bowker/PDRA)
The FX cars will feature dimensionally stock bodywork, in fact the roof and rear quarter-panels must be original steel pressings. Doors must be dimensionally stock and fully operational. The cars’ bodywork must be stock-appearing, and that includes bumper covers, (front and rear) which must be consistent with the manufacturer, model, and model year claimed.
All entries must be equipped with a stock grille of the same configuration and design for the specific body used, and complete headlight and tail light assemblies must be retained in the original factory location.
Tubular framework
The bodywork will be just an outer skin on the FX cars, as they will feature a tubular 4130 chromoly chassis built to SFI specs. Arguably this will make the FX class will be more accessible than the FSS class, as it will be possible to buy a salvaged vehicle to get the basic panels as a basis for a new car build, as opposed to buying one of the OEM-produced FSS vehicles.
The FX class will have a minimum weight limit of 2650 lb, 625 lb lighter than the lightest permitted FSS cars and 300 lb heavier than PS cars.
OEM powerplants
The engine combinations will be directly interchangeable with those used in the FSS class. The engine used must be of the same manufacturer as the body. The permitted engines are as follows (horsepower figures are those quoted by the manufacturer):
GM LS7 350 c in (supplied in the Chevrolet COPO Camaro)
- 630 bhp fitted with 2.65 litre Magnuson Roots-type supercharger
- Upper supercharger pulley size: 3.125 in
- Supercharger rear jack shaft cog pulley: 32 teeth
- Supercharger rear cog pulley: 34 teeth
- Lower engine pulley: 8.000 in
Chrysler GEN3 Hemi 354 cu in (supplied in the Dodge Challenger Drag Pak)
- 630 bhp fitted with 3.0 litre Whipple screw-type supercharger
- Upper supercharger pulley size: 3.375 in
- Lower engine pulley: 8.000 in
Ford Coyote 326 cu in (found in the 2019 Mustang Cobra Jet)
- 610 bhp fitted with 3.0 litre Whipple screw-type supercharger
- Upper supercharger pulley size: 3.750 in
- Lower engine pulley: 6.938 in
The fact that the permitted engine combinations are based on stock OEM engines available on the showroom floor is a step to making the class relatable to the general public. Modifications to the engines are permitted however, within certain parameters.
Starting at the top of the engine, the supercharger, throttle body and inlet manifold must be unmodified; sand blasting, dry coating and flash removal are specifically prohibited. The supercharger overdrive ratios are outlined in the basic engine specifications.
The superchargers used all contain integrated charge coolers, which cannot be modified, and the charge cooler tank must be of standard volume. This prevents competitors building a large ‘ice box’, a high-volume tank in which ice can be contained, so that ice-cold water is pumped through the charge cooler, reducing inlet air temperature.
Larger fuel injectors are permitted, providing they are installed in the stock locations. The only engine ECUs permitted are the Holley HP and the Holley Dominator. External sensors not pertaining to the engine functions may not be connected to the ECU, but a standalone data logger such as a Racepak may be used to log chassis and driveline functions.
Moving on to the cylinder heads, porting of the intake runner, exhaust runner and combustion chamber are permitted, and can be performed via CNC operations. However, relocating the intake or exhaust port opening is prohibited, furthermore the intake side of head may not be cut into any part of the OEM positioned valve cover bolt holes or intake mounting holes, effectively putting a limit to how far the intake porting can go.
Changing the configuration of the combustion chamber (by turning a hemispherical chamber into a rotated wedge-style chamber, for example) is prohibited, specifically the spark plug hole must maintain the stock OEM location, size and angle. Valve-guide centrelines must maintain the stock lateral and front-to-back location as machined by the OE manufacturer.
The cylinder heads must retain their original sized valves, placed at their original angles (within a tolerance of ±1º). The intake and exhaust runner both have a maximum volume, and the combustion chamber has a minimum volume, as outlined in the NHRA engine blueprint specifications.
Inlet and exhaust manifold adapter plates are prohibited, and O-ringing of the cylinder head or block – where a ring typically made of stainless steel is inserted into the cylinder head or the block around the cylinder, and a corresponding groove is cut into the opposing face in order to create a better head gasket seal – is also prohibited. However, cylinder head bolts can be switched to aftermarket studs.
Regarding the valvetrain, aftermarket (higher rate) valve springs are permitted, as well as aftermarket valves, pushrods and rocker arms (including larger mounting hardware).
The engine block must be the original type for the engine platform used; the NHRA does however permit certain aftermarket blocks. The cylinder bores must not exceed 0.080 in over stock diameter.
Aftermarket pistons, rods and crankshaft are permitted, although they must retain the OEM configuration (effectively outlawing revised journal diameters and flat-plane crankshafts). An aftermarket SFI Spec 18.1 harmonic balancer is mandatory.
Interestingly, the crankshaft height is fixed at a minimum of 13 in from the ground at ride height. This allows the use of an OEM wet sump. Dry-sump systems are specifically prohibited.
Drivetrain
The FX class mandates use of an SFI 1.5 spec three-disc clutch with a minimum disc diameter of 8 in. The standard OEM starter motor location is mandatory. This prevents the use of small-diameter flywheels, as the OEM starter ring diameter must be maintained.
The clutch must be manually operated via mechanical means, no hydraulics or pneumatics are permitted. The clutch design is referred to as a ‘pedal clutch’, meaning that springs (that can be preloaded) apply clamping pressure upon pedal release, creating torque capacity (and an amount of clutch slippage). These springs are assisted by the release levers that have calibrated weights mounted on them; centrifugal force causes the levers to apply additional clamping force on the clutch plates, increasing the torque capacity. This system allows clutch slippage that is tuneable, with full lockup achievable at high engine RPM.
The clutch must be housed in an SFI spec 6.3 bellhousing. This is a full containment unit, and provides positive location on the engine block and separate anti-rotation mounting points that attach to the rear engine mounting plate.
The transmission used must be a manually shifted five-speed planetary style or clutchless type. It is expected that most competitors will use a Liberty twin-layshaft transmission, as used in Pro Stock. The clutch will therefore be operated by the driver only on launch, not on gear change.
The rear tyre size is set at a mandatory 33.0 x 10.5W-15 (the W denotes wide; the tread width of these 10.5 in tyres is actually more than 11 in). The tyres will be mounted on a 16 x 16 in double beadlock wheel, which serves to ‘stretch’ the tyres tread width further.
The suspension on these tube frame cars will bear no relation to their OEM production counterparts, and will be more akin to PS cars in terms of design. Aftermarket MacPherson-type struts will be used on the front of these cars and a four-link rear suspension will be used to provide adequate traction. The damping rate cannot be adjusted on track, and digressive springs are prohibited, as are inerter-type dampers.
It could be said that the heavy engine regulation in the FX category will stifle innovation, but many of the rules for the FX class are aimed at keeping costs at a sustainable level, and keeping the cars relatable to spectators and fans.
The FX class will offer an increased level of performance over their FSS counterparts but will still be behind PS cars when it comes to ETs and speeds.
The permitted engines currently running in FSS, when built by companies such as BES, Patterson Elite and Holbrook Racing Engines, are producing around 1600 bhp. With a minimum weight of 2650 lbs it is expected to see the FX cars debut by running the quarter-mile in 6.7 seconds at around 200 mph.
NHRA Factory X will start midway through 2022 as an exhibition category at select NHRA Camping World Drag Racing Series events.