Pro 10.5 Rules

UPDATED 10/6/25

OVERVIEW

The framework of the 2025-2026 Drag Illustrated Winter Series Rules and Regulations was proposed and agreed upon by series and event officials on October 1st, 2025.

The Drag Illustrated Winter Series strictly adheres to the safety and race procedure standards and guidelines of the National Hot Rod Association (NHRA). The 2025 NHRA Rulebook is available for download by clicking here.

PRO 10.5

WEIGHT MINIMUMS

ALL WEIGHTS INCLUDE DRIVER AT CONCLUSION OF RUN.
DUAL POWER ADDER TYPES PROHIBITED.

Naturally Aspirated, Small Block – No Minimum
Naturally Aspirated, Big Block – No Minimum

NITROUS OXIDE, SMALL BLOCK

Nitrous (Stock Bore Spacing) – No Minimum
Nitrous (Non-Stock Bore Spacing) – 2,050 lbs.

NITROUS OXIDE, BIG BLOCK

Nitrous (4.84/4.90 Bore Spacing) – 2,065 lbs.
Nitrous (5.0 Bore Spacing) – 2,165 lbs.
Nitrous (5.2 Bore Spacing) – 2,365 lbs.
Nitrous (5.3 Bore Spacing, max 965 CID) – 2,600 lbs.
Nitrous (5.3 Max Bore Spacing, over 965) – 2,615 lbs.

SMALL BLOCK, TURBOCHARGER

Single Turbocharger (Non-Stock Bore Spacing) – 2,525 lbs.
Single Turbocharger (HEMI-Head, Stock Bore Spacing) – 2,550 lbs.
Single Turbocharger (Stock Bore Spacing) – 2,450 lbs.
Single Turbocharger (HEMI-Head, Non-Stock Bore Spacing) – 2,625 lbs.
Twin Turbocharger (88mm & Smaller, Stock Bore Spacing, less than 430 CID) – 2,400 lbs.
Twin Turbocharger (88mm & Smaller, Stock Bore Spacing) – 2,525 lbs.
Twin Turbocharger (88mm & Smaller, Non-Stock Bore Spacing) – 2,600 lbs.
Twin Turbocharger (88mm & Smaller, HEMI-Head, Stock Bore Spacing) – 2,600 lbs. • Twin Turbocharger (88mm & Smaller, HEMI-Head, Non-Stock Bore Spacing) – 2,675 lbs.
Twin Turbocharger (91-94mm, Stock Bore Spacing) – 2,600 lbs.
Twin Turbocharger (91-94mm, Non-Stock Bore Spacing) – 2,675 lbs.
Twin Turbocharger (91-94mm, HEMI-Head, Stock Bore Spacing) – 2,700 lbs.
Twin Turbocharger (91-94mm, HEMI-Head, Non-Stock Bore Spacing) – 2,775 lbs.

BIG BLOCK, TURBOCHARGER

Single Turbocharger (Conv. Head) – 2,500 lbs.
Single Turbocharger (Non-Conv. Head) – 2,575 lbs.
Twin Turbocharger (88mm & Smaller, Conv. Head, Stock Bore Spacing, less than 550 CID) – 2,600 lbs.
Twin Turbocharger (88mm & Smaller) – 2,750 lbs.
Twin Turbocharger (91-94mm, Conv. Head, Stock Bore Spacing, less than 550 CID) – 2,650 lbs.
Twin Turbocharger (91-94mm) – 2,800 lbs.

481X/HEMI, TURBOCHARGER

Single Turbocharger (481X) – 2,575 lbs.
Single Turbocharger (HEMI, 4.8 Bore Space) – 2,650 lbs.
Single Turbocharger (HEMI, 4.9 Bore Space) – 2,675 lbs.
Twin Turbocharger (481X, 88mm & Smaller) – 2,750 lbs.
Twin Turbocharger (481X, 91-94mm) – 2,800 lbs.
Twin Turbocharger (HEMI, 4.8, 88mm & Smaller) – 2,825 lbs.
Twin Turbocharger (HEMI, 4.8, 91-94mm) – 2,900 lbs.
Twin Turbocharger (HEMI, 4.9, 88mm & Smaller) – 2,850 lbs.
Twin Turbocharger (HEMI, 4.9, 91-94mm) – 2,925 lbs.

SMALL BLOCK, CENTRIFUGAL

Centrifugal (Conv. Head, Stock Bore Spacing) – 2,400 lbs.
Centrifugal (Conv. Head, Non-Stock Bore Spacing) – 2,475 lbs.
Centrifugal (Non-Conv. Head, Stock Bore Spacing) – 2,500 lbs.
Centrifugal (Non-Conv. Head, Non-Stock Bore Spacing) – 2,575 lbs.

BIG BLOCK, CENTRIFUGAL

Centrifugal (Conv. Head, Stock Bore Spacing, less than 550 CID) – 2,575 lbs.
Centrifugal – 2,625 lbs.

481X/HEMI, CENTRIFUGAL

Centrifugal (481X) – 2,650 lbs. (-25)
Centrifugal (HEMI, 4.8 Bore Space) – 2,800 lbs.
Centrifugal (HEMI, 4.9 Bore Space) – 2,825 lbs.

SMALL BLOCK, SUPERCHARGER

Roots (Conv. Head, Stock Bore Spacing) – 2,400 lbs.
Roots (Conv. Head, Non-Stock Bore Spacing) – 2,475 lbs.
Roots (Non-Conv. Head, Stock Bore Spacing) – 2,500 lbs.
Roots (Non-Conv. Head, Non-Stock Bore Spacing) – 2,575 lbs.
Screw (Conv. Head, Stock Bore Spacing) – 2,700 lbs.
Screw (Conv. Head, Non-Stock Bore Spacing) – 2,775 lbs.
Screw (Non-Conv. Head, Stock Bore Spacing) – 2,800 lbs.
Screw (Non-Conv. Head, Non-Stock Bore Spacing) – 2,875 lbs.

BIG BLOCK, SUPERCHARGER

Roots (Conv. Head) – 2,575 lbs.
Roots (Non-Conv. Head) – 2,625 lbs.
D-Rotor Screw (125% Max Overdrive, Conv. Head) – 2,775 lbs.
D-Rotor Screw (125% Max Overdrive, Non-Conv. Head) – 2,850 lbs.
C-Rotor Screw (92% Max Overdrive, Conv. Head) – 2,725 lbs.
C-Rotor Screw (92% Max Overdrive, Non-Conv. Head) – 2,775 lbs.
C-Rotor Screw (110% Max Overdrive, Conv. Head) – 2,825 lbs.
C-Rotor Screw (110% Max Overdrive, Non-Conv. Head) – 2,875 lbs.

481X/HEMI, SUPERCHARGER

Roots (481X/HEMI, 4.8 Bore Space) – 2,625 lbs.
Roots (HEMI, 4.9 Bore Space) – 2,650 lbs.
D-Rotor Screw (125% Max Overdrive, 481X/HEMI, 4.8 Bore Space) – 2,800 lbs.
D-Rotor Screw (125% Max Overdrive, HEMI, 4.9 Bore Space) – 2,825 lbs.
C-Rotor Screw (92% Max Overdrive, 481X/HEMI, 4.8 Bore Space) – 2,875 lbs.
C-Rotor Screw (92% Max Overdrive, HEMI, 4.9 Bore Space) – 2,900 lbs.
C-Rotor Screw (110% Max Overdrive, 481X/HEMI, 4.8 Bore Space) – 2,900 lbs.
C-Rotor Screw (110% Max Overdrive, HEMI, 4.9 Bore Space) – 2,925 lbs.

INLINE 4 & 6 CYLINDER

350 CID and Smaller – No Minimum Weight
351-499 CID – Small Block Weight for Combination
500-670 CID – Big Block Weight for Combination

WEIGHT ADDITIONS/REDUCTIONS

Add 25 lbs. for Transmission with four (4) or more forward gears, excluding clutch applications.
Add 25 lbs. for Round Tube Frame Rails from Firewall Forward
Add 50 lbs. for Lock-Up Transmission.
Add 25 lbs. for Non-Factory Engine Placement more than 4 inches *
Deduct 25 lbs. for Factory Engine Placement + or – 3 inches *
Deduct 25 lbs. for Nostalgia Body Style, see body section.
Deduct 50 lbs. for Cast Cylinder Heads -OR- Cast Engine Block
Deduct 50 lbs. for 118mm for Smaller Single Turbocharger.
Deduct 50 lbs. for F3R-136 Centrifugal Supercharger.
Deduct 50 lbs. for Boosted Combination using Gasoline as Fuel
* Set back is determined by a plumb line dropped from the center line of the rear axle and where engine meets the transmission.
*78 inches minimum allowed distance, any less than 80 inches add 25 lbs. which will be added to the + 25 lbs. above.

ALL RULES ARE SUBJECT TO CHANGE TO ADJUST PARODY IN THE EVENT OF PERFORMANCE ADVANTAGES DUE TO ENGINE/TRANSMISSION COMBINATION, CHASSIS, POWER ADDER, BODY ENHANCEMENTS, ETC.

REQUIREMENTS & SPECIFICATIONS

ENGINE: 1

COOLING SYSTEM
Radiator permitted, electrically driven fan and water pump is permitted.

CYLINDER HEADS
Billet heads are permitted. Maximum one spark plug per cylinder. Maximum two valves per cylinder. Modular engines combinations are allowed four valves per cylinder.

CYLINDER BORE SPACING
Bore spacing is set at maximum of 5.300-inches for nitrous oxide engines. Bore spacing is set at maximum of 5.000-inches for all supercharged applications. Bore spacing is set at maximum of 5.300-inches for turbocharged applications. Small Block combinations must retain 4.600 bore spacing.

ENGINE
Maximum Small Block bore spacing is limited to 4.600 bore spacing on all entries and a 540 cubic inch maximum. AMC/Pontiac combination is accepted as OEM bore space and deck height as small block combination. Nitrous entries are limited to maximum bore spacing of 5.300 and limited to a maximum deck height of 12.600-inches. Maximum Big Block bore spacing on Supercharged is 5.000 inches. Maximum Big Block bore spacing on Turbocharged is 5.300 inches and limited to 670 cubic inches. Screw supercharged combinations are limited to a maximum of 540 cubic inches.

EXHAUST
Automotive type system designed specifically for racing required, zoomie and/or bullhorn- style headers are permitted on all combinations. Exhaust gases must be directed out of the body towards the rear of vehicle and away from the driver, fuel system and timing or staging beams. All removable multi-piece exhaust collectors/stacks must be securely fastened with either an NHRA-accepted header tether, a minimum .050-inch (half-inch) stitch weld located on each primary tube or be permanently attached to the vehicle or frame with positive fasteners (i.e., exhaust hangers, support brackets, bolts/nuts, etc.) such that they require tools for removal.

FUEL
Racing gasoline and methanol allowed, M5 prohibited. The use of nitromethane and/or propylene oxide is strictly prohibited. The use of fuel additives is PROHIBITED.

INDUCTION
Any number and type of carburetors or throttle bodies may be used. Electronic fuel injection permitted.

INTERCOOLER
Any intercooler is permitted on gasoline combinations only. Must be securely mounted to chassis or mounts with preferred hardware. Water box must be contained in a safe environment with a locking or screw-on top to enclose water/ice during the run. Intercooler combined with a methanol fueled combination is prohibited. Inline 4- & 6-Cylinder combinations permitted intercooler with methanol as fuel.

NITROUS OXIDE
Permitted, any type of multi-stage nitrous system with no restrictions. All nitrous bottles must be stamped as meeting minimum DOT-1800-pound rating. The nitrous system is limited to two bottles only, maximum of 15- pounds for each nitrous bottle. No external bottles/lines can be connected to the nitrous bottles or system. Push systems are prohibited. Each bottle must have only one feed outlet and one vent outlet with no other connections. Each bottle must be individually vented. Gauge port on one bottle may be plumbed to a low-pressure regulator. Any plumbing leading from the gauge port may be traced for clarity and verification at any time. Dual power adders are strictly prohibited across all combinations. Commercially available blanket-type warmers are accepted while the use of a torch or any other external heating of bottle(s) is prohibited.

SUPERCHARGER
Permitted. Centrifugal, 14-71 Roots superchargers and screw ‘C’ and ‘D’ rotor superchargers only. No Whipple superchargers. 110% overdrive restriction on ‘C’ rotor screw superchargers. 125% overdrive restriction on ‘D’ rotor screw superchargers. Manifold burst panel meeting SFI Spec 23.1 plus restraint system meeting SFI Spec 14.2.1, including injector restraint straps are mandatory. The supercharger restraint straps, and fuel lines must be installed such that when the restraint straps are fully extended, no load is placed on any of the fuel lines. Intercoolers, variable multi-speed supercharger devices are prohibited. The top opening of the roots supercharger may not exceed 12 inches in length or 5 inches in width. The entire inlet opening must be on/in the upper surface only. The maximum length from the front of the supercharger drive pulley to the leading edge of the rotor is 15 inches. Offset drive pulleys, spacers, modified cases, or attaching methods may not be used to add to the 15-inch maximum. All manifold configurations, supercharger modifications and locations must be accepted prior to competition. The rotors must be driven from the front (both the external drive and the internal gearing. Any inlet/outlet cavity in front of the rotors is restricted to a maximum of 3.000 inches measuring from the face of the bearing plate to the front of the cavity. Supercharger openings must be fixed from the water box until the conclusion of the run. Centrifugal superchargers are permitted a compressor inducer diameter of 5.47- inches/138.9mm and a compressor exducer diameter of 7.22- inches/183.39mm. Measurement will be taken at the point where the leading edge of the compressor wheel meets the inlet housing. All centrifugal superchargers must have a ballistic blanket installed on the compressor housing. No rear gear restriction. Dual power adders are strictly prohibited across all combinations. All forms of power adders must be commercially available to the general public for purchase and use.

TURBOCHARGER
Permitted, single turbocharger combinations are limited to a maximum 134mm unit. Twin turbocharger combinations are limited to a maximum of two (2) 94mm units. The maximum diameter of the housing bore at the leading edge of the wheel may not exceed 2mm more than the maximum allowable turbocharger size permitted. All turbochargers must meet SFI Spec 61.1 and are required to have a ballistic compressor blanket installed on the compressor housings. Non-SFI turbos are accepted but required to run ballistic blankets. All turbochargers must have cross bolts in the exhaust to prevent the turbine from being discharged in the event of failure. Cross bolts are to be 3/8” grade 5 minimum and mounted within 1” of the turbine discharge flange. Turbochargers will be verified by measuring the housing bore at the leading edge of the impeller wheel and must retain the contour of the compressor housing, stepped or clipped compressor wheels are prohibited. Inserts or reducers to achieve inlet or outlet dimensions are prohibited. Any inconsistent modifications to compressor or turbine wheel, blades, hubs, cover, or housing beyond accepted commercially available manufacturing process is PROHIBITED. Dual power adders are strictly prohibited across all combinations. All forms of power adders must be commercially available to the general public for purchase and use.

DRIVETRAIN: 2

CLUTCH, FLYWHEEL, FLYWHEEL SHIELD & MOTOR PLATE
Clutch and flywheel meeting SFI 1.3, 1.4 or 1.5 certification required. SFI 29.1 flex plate required on all torque converter equipped cars (SFI 29.2 recommended). The motor plate must be attached to the chassis using at least two welded mounting points with a minimum 3/8-inch Grade 8 bolts and full nuts. At least two additional welded mounting points (using the motor plate, front block plates, etc.) are required to secure the engine to the chassis also with minimum 3/8-inch Grade 8 bolts and full nuts.

DRIVELINE
A full 360-degree driveshaft tube is required over yoke, extended a minimum of 12-inches required from transmission tail shaft. Minimum thickness of tube housing is .050-inches chrome moly or titanium. Two-piece units accepted with a minimum of six (6) 3/8-inches Grade 8 bolts. SFI 43.1 driveshaft required.

FLYWHEEL SHIELD
SFI 6.3 certification required.

TRANSMISSION
Any transmission permitted. Lock-Up transmission/converter setups are permitted. All transmissions must be covered by a one-piece SFI 4.1 restraint

BRAKES & SUSPENSION: 3

BRAKES
Four wheel brakes with dual mater cylinder mounted above the frame rails is required.

REAR END
Automotive type rear end required. Titanium wheel studs prohibited.

SUSPENSION
Race car type suspension required. Solid suspension is prohibited. Shock absorbers required on all four wheels.

WHEELIE BARS
Permitted.

FRAME: 4

CHASSIS
SFI certification required, can be NHRA or PDRA.

FRAME
Door cars only, no altered or roadsters. Back-half style cars are permitted. Factory front frame rails must be fully intact from the firewall to 4” forward of the front spindle. Minor notching of the front frame is allowed for clearance and safety reasonings. Round tube frame rails from the firewall forward will adhere to a weight penalty. Aftermarket front k-members are permitted, must bolt in the factory location. Factory equipped “bolt-in” subframe cars are permitted an aftermarket bolt-on front end (Ex. Smith Racecraft) for ’62-’74 Nova and ’67-81 Camaro/Firebird, must bolt-in. Factory wheelbase for year/make/model must be maintained, (+/- 2 inches).

GROUND CLEARANCE
A minimum of 3-inches of ground clearance is mandatory from the front of the vehicle to 12-inches behind the centerline of the front axle. A minimum of 2-inches of ground clearance is mandatory for the remainder of vehicle, except oil pan and exhaust headers

WHEELBASE
Factory wheelbase for year/make/model must be maintained, plus or minus two (2) inches.

TIRES & WHEELS: 5

TIRES
Maximum tire size is 33×10.5W bias ply slick only. Any radial tire option is prohibited, bias ply tires only.

BODY: 6

BODY
The car must retain its original appearance and profiles. Full aftermarket composite is permitted, but must retain factory appearance, profiles, and dimensions. Pro Mod and Pro Stock bodies are not permitted. Factory dimension quarter panels must be used with front to rear door opening in factory dimension. Quarter panels must be of factory appearance, external wheel tubs are not permitted. Fiberglass/carbon fiber body parts are limited to hood, fenders, doors, deck lid, roof skin and bumpers unless car is composite from factory. Maximum front overhang of 45” as measured from the centerline of the front spindle. Must retain factory body lines with removable composite components as in hood, front bumper, front fenders, doors, and deck lid. Any beam tripping device forward of the bumper may be a maximum of six-inches in length and must retain the 45” maximum front overhang measurement from center of spindle. A hood must be used; scoop or hood must cover entire induction system. Exceptions are throttle bodies or carburetors on naturally aspirated and nitrous oxide assisted engines, along with intake manifold/throttle bodies on boosted applications. Those may protrude through the hood for clearance, if needed. Carburetors are required to be covered at all times. Forward facing hood scoops/inlets are permitted. All vehicles must be professional finished, painted, lettered, numbered, and decaled.

NOSTALGIA BODY STYLE
The following body styles may deduct 25 pounds from their minimum weight: 1937-1938 Chevy, 1937-1942 Willys, 1949-1950 Mercury, 1953-1959 Studebaker, 1953-1963 Corvette, 1955-1957 Chevrolet, 1955-1957 Buick, 1968-1972 Chevelle and Oldsmobile. Full size truck bodies (Silverado, FSeries, Ram, etc.) are also eligible for the body deduction.