Hobby Stock


2014 Hobby Stock Rules:

UPDATED 03-12-2014

Cars or Trucks must be a stock street type. American made passenger cars or trucks only. No 4 wheel drive or front wheel drive vehicles.  Novas & Cameros along with Trucks of 1500 series or smaller allowed.  Steel or Aluminum factory style OEM body is permitted.  Roofs, trunks and hoods must be factory Steel.  Doors must be welded or bolted shut. Doors may be gutted for cage installation. All glass, plastic, fiberglass and trim must be removed from race car. Upholstery and plastic portion of the dash must be completely removed. A-posts may be trimmed and cleaned up to allow for engine set back, but must be reinforced. Window post may not be removed. All bodies must be proportionate to the year and make of frame. OPTION:  Performance Bodies “Classic Dirt Noses” as shown on page 35 of their catalog will be allowed but must be mounted vertical as original manufacture intended.  NO SLOPED LATE MODEL STYLE FRONT BUMPERS OR NOSE.

Frame must remain square and to factory specs. Metric frame, (Monte Carlo, Thunderbird) cars are allowed. Nova’s allowed. Only metric framed station wagons are permitted with enclosed rear compartment, no other makes or models will be accepted. No Town Cars, Mustangs or Corvettes. No commercial vehicles, convertibles or sports cars. Minimum wheel base must be OEM specifications for stock factory production. Allowance of ½” for caster adjustment will be allowed at the technical inspection pad. Chevy, Ford and Dodge trucks are also allowed.

Firewalls must be complete, from fender to fender, top to bottom with all holes covered with 20 gauge steel minimum. Floor may be cut to allow firewall clearance for headers and distributor, but area must be closed with 20 gauge steel. Stock floor pan must extend from front firewall to rear fire wall. All rusted portions of the floorboard must be replaced with minimum 20 gauge steel. Driver compartment may be enclosed with 20 gauge steel with complete interior window level decking (may be aluminum). If compartment enclosed, and decking in place, rear firewall may be removed, floor pan must remain from front firewall to no less than 25 inches forward of rear axle centerline.

Driver location:
Driver must be on left side of drive shaft. Fender wells may be altered or removed. No part of driver’s seat shall be less than 30 inches forward of left rear axle centerline. Driver must be located in the original OEM seat location on the left side of the vehicle only. No back seat mounting of driver’s seat.

Minimum weight is 3200 pounds with driver after race.

Holley #4412 two barrel on all engines other than GM Crate # 602.  GM Crate motors will be allowed to run any Holley 4 bbl. carburetor (maximum 650 cfm), all components (float bowls and main body) must be Holley manufactured.  Metering blocks and base plate may be billet aluminum non-Holley.  No aerosol-style carburetors allowed.  May use Speedway Motors part # 545-64940 or Moroso part #64940 carburetor spacer on crate.   Choke horn on #4412 must be attached. Circle track floats may be used.  Number must be legible on air horn. No machine work on carburetor.  Holley #4412 carburetors may be mounted on a stock 4 bbl.cast iron or Stock low profile Aluminum 4 bbl. intake with an adaptor, (max. 2”),  or on a Victor Jr. (Part # 2901), 2bbl. manifold, (Adaptor not allowed on Victor Jr. intake).  No other alterations are allowed. Only one carburetor allowed on engine. No other carburetors are allowed. No injectors or pressure systems allowed. Carburetor must pass a go-no-go gauge.

Cylinder Heads:
EQ heads as produced and assembled from manufacturer, no modifications allowed, 7/16 studs, as produced and assembled from manufacturer will be legal.  Absolutely no casting removal in valve pocket of EQ for any reason.  No closed chamber heads except 305 heads on 305 engine only. No partially closed chamber heads. No 461 or 462 heads. Open chamber heads only. Race cars using GM engines must run 350 heads on 350 engines, and 305 heads on 305 engines. No aluminum heads.  All GM heads are limited to 1.94” intake valves and 1.50” exhaust valves. Heads may be flat milled for surfacing reasons only, no angle milling allowed. Studs may be pinned or screwed in. Push rod guide plates are allowed. Any single valve spring with dampener is legal. No double, triple, or beehive style springs allowed. No porting, polishing, port matching or coatings of any type allowed. No aluminum or titanium components are allowed. Any work done in the bowl area must be done with a 360 degree cut, with the valve guide as the center point. Full roller rocker arms and/or roller tip rocker arms are not allowed. Poly-locks are allowed. Stud girdles are not allowed.


Number One spark plug may not extend further back than the center of the upper ball joint on any car. Cast iron OEM blocks only. After-market steel, stock type engine mounts are allowed. No machining in lifter valley (except for oil flow drain openings) or in lifter bores. Engine Rotating assemblies must be stock, or stock appearing. No lightweight cranks allowed. No knife edge, no bull nosing, undercut or drilling of second or third rod journal throws allowed. Rods must be 5.7” rods only. 3:48” stroke only. Minimum weight for crankshaft is 49 lbs.  No Chevrolet bowtie, Ford SVO or Mopar performance blocks. Stock stroke must be maintained. After-market rod bolts may be used. Only Stock style pistons with two (2) or four (4) equal valve reliefs are allowed.  Pistons may be cast or forged.  Floating wrist pins are allowed. Flat top pistons or dish pistons only, no domed pistons.  No total seal type rings are allowed. Maximum cubic inch displacement allowed is 361 c.i.d.  Boring to a maximum of .060” over stock OEM bore is allowed. Fords: 289, 302, or 351 blocks only with flat top pistons. Any OEM Ford head is allowed. No after-market Ford or Boss heads allowed. Maximum valve size is 1.94” intake and 1.50” exhaust. Only 273, 318, 340 and 360 blocks can be used for Mopar. No big blocks. (OEM blocks only. No Hemi’s).  Again: only, Ford, Chevy or Mopar engines are allowed. Mopar= Chrysler, Plymouth and Dodge. 360 cubic inch maximum. Ford= Ford and Mercury. 360 cubic inch maximum. Chevy= Pontiac, Buick, Oldsmobile as long as they are Chevrolet engines. 361 cubic inch maximum. Stock style rockers arms only, no full rollers and/or roller tips allowed.  No stud girdles. A stock oil pan or a claimer style pan is allowed. Oiling must be complete wet sump. No dry sump systems allowed. After-market harmonic balancer is allowed. Engine must have 1” sight plug in oil pan between the second and third pan bolt on the driver’s side. No obstruction of sight through inspection hole inside of pan.
Compression rule is 175 lbs. per cylinder with all spark plugs removed and the engine turned over 5 times.

Any Hydraulic Flat Tappet Cam, Lifter, Push Rod & Rocker Arm Combination is allowed as long as the total opening of the valve does not exceed .450.  No Rollers (This includes Cam, Lifters or Rockers).  (This .450 measurement will be done at the Retainer).

Cast iron or the following Aluminum intakes only.  (Edelbrock Gm#2701, GM #12366573, Vortec 2116, Edelbrock 7116 or a Victor Jr. (Part #2901).  No high rise intakes, No Brzezinski intakes. No porting, polishing, port matching, acid porting, acid treatments or coatings of any kind. Any brand, style or size air cleaner are allowed, but no type of RAM air or forced air induction will be allowed. Any valve cover combination allowed.

Water Pump:
Cast iron water pump is required. Pulleys may be aluminum after-market. Fan must be steel and attached to water pump. Fan spacers may be used. An additional electric cooling fan may be used to assist cooling under yellow flag conditions, but all stock fan, pulley and belt components must remain installed.

Ignition must remain under stock OEM cap. Stock HEI ignition is allowed. No MSD systems or any after-market or GM ignition boxes allowed. No external coils.  All cars must have ignition switch clearly labeled. The car must be equipped with a kill switch to be located within reach when standing outside the car and easily accessible to emergency personnel.

Only under chassis style headers allowed. No 180 degree headers. No cross over headers. No step headers. Stock cast iron exhaust manifolds allowed. All exhaust pipes must extend past driver seat or exit to outside of car.

Only one radiator may be used. Radiator must be in stock location.  No cutting of hood for clearance. Aluminum radiator is allowed. Racing radiator cap is allowed.

Fuel System:
Gasoline ONLY. Racing fuel allowed. NO additives allowed. NO alcohol.  Fuel pump must be stock OEM style. Carter and Holley manual styles are allowed.  Fuel cell must be securely mounted to frame in trunk of car between the rear frame rails. Fuel cell incased in a steel container is required if cell is dropped down between frame rails. A plastic fuel cell may be used only if complete floor pan is in place. Fuel cell is mandatory, maximum capacity of 22 gallons.

Any OEM automatic transmission is allowed. Unit must be stock and have a full working torque converter, minimum of 10”. Powerglides must have 10” torque converter. No direct drives, valve controlled pumps, or bleeder style valve bodies. All forward, neutral and reverse gears must be in working order for all automatics, except Powerglides. Powerglides are allowed either one or both forward gears, with neutral and reverse in working order.  Car must be able to sit still in gear at 1,800 rpm’s with the brakes being applied and not kill engine.

Standard transmissions must be OEM stock, with all gears in working order and a minimum of 10.5” clutch, pressure plate and full size stock flywheel. No mini-clutches or direct drives. Standard transmissions may not use aluminum flywheel of any size. All standard transmissions must have bell housing made of ¼” thick steel and must cover 180 degrees over the sides and top of the clutch assembly (also referred to as a blow-proof bell housing).4-speed manual transmission will be allowed. No 5-speed or 6-speed manual transmissions or overdrive units. No Bert, Brinn or internal clutch style transmissions allowed. No ram couplers allowed. Quick-change transmissions or transmission adapters for gear change are not allowed.
Cars must be self-starting and have working neutral, reverse and ALL forward gears. (example: 3-speed trans. Must have 3 forward working gears.

Transmission fluid coolers are allowed, but may not be mounted exposed in drivers compartment.

Drive shaft must be steel and must be painted white or silver. Drive shaft must have a steel drive shaft loop (360 degrees) connected to the frame located within 6” of the front drive shaft u-joint. Minimum size of drive shaft loop is 2” X ¼” or minimum of 1” round tubing. No chain loops are allowed as drive shaft loops.

Rear End:
Rear-end must be stock for year, make and model. Any gear ratio allowed as long as no altering of housing is required to allow for installation. 8.5 rear-end may replace 7.5 Must use stock OEM, for frame being used, length upper and lower control arms.  Axles must be locked together at all times with mini-spool or welded. No posi-trac, limited slip, Detroit locker of full spool allowed.  Pinion angle may not be altered.

Racing brake pedal and single racing master cylinder are allowed. No aluminum brake components on car. A minimum of (3) functioning brakes at all times are required.  If (4) brakes are installed, a cut-off valve may be used on one of the brakes. Cut-off valve may not be within reach of driver compartment. Adjustable proportioning valves are not allowed. If using (3) brakes, the 4th brake components need not be present other than the rotor, which you can remove outer portion. Rear disc brakes are allowed with steel components only and with only a single piston caliper.

Quick-steer of any type or style are allowed. Complete OEM stock steering system for year, make and model, from the steering box to the spindles, including steering gear box, must be used. Cast iron steering box only. After-market steering shaft and quick release steering wheel is allowed. Steering wheel spacer allowed to a maximum of 3” thick.

No modifying of the suspension is allowed. Exception:  Upper control arm brackets may be moved for caster and camber adjustment.  Cannot move lower A-Frames.  OEM suspension parts only. OPTION: IMCA TUBULAR UPPER CONTROL ARMS WILL BE PERMITTED (steel only and must be IMCA stamped, non-adjustable).  Non-Metric cars will be allowed to run steel, non-adjustable, OEM length tubular upper A-Arms.   No cutting, welding or bending of frame to accommodate suspension changes.  All other suspension parts must remain absolutely stock for that year, make and model of car. This includes spindles, rotors, lower control arms, ball joints, tie-rods, tie-rod sleeves, center-link, pitman arm, idler arm, steering box and trailing arms. No adjustable spring spacers. All upper/lower trailing arm and upper/lower control arm bushings must be present; however, they may be replaced with steel after-market bushings. No mono-ball bushings. Bolt on spindle savers are allowed. Upper control arm can be strengthened with a maximum of 3/8 inch cold roll or rebar along outer lip with the groove.

Racing springs may be used. Maximum coil spring length is 13”. Rear coil spring must not extend through the stock OEM upper spring bucket. Adjusta ble spring bucket allowed on rear only. Leaf springs may be after-market, (steel only) but no adjustable lowering blocks.   Any steel non-jack bolt type leaf spring shackles are allowed, including multi-hole.  No sliders. Springs must be mounted in OEM location top and bottom.

Racing Shocks are allowed but must be steel, OEM replacement shocks.   Shocks must be mounted using the stock mounts in the factory installed locations.  No heims on shocks allowed. No shock adapters.

Roll Cage:
Roll bars must be constructed of 1.5” X 0.95” steel tubing minimum.

Main roll bar and halo must be a minimum of 1” higher than the drivers helmet.

Minimum of (3) door bars on the driver side and a minimum of (2) on the passenger side. Front loop is allowed to protect radiator and front frame arms. Front core support may be removed and can not be extended past hood. Maximum size is 1.5” O.D., 0.95” tubing. All roll cage welds must be complete and pass safety inspection by tech officials.

Floor pan may be cut for cage and sub-frame connectors, but must be replaced by a minimum of 20 gauge steel. X-bracing under the driver (frame to frame) is allowed.

Rub Rails:
A single rub rail is allowed on each side of car. Maximum size is 1.5” X 0.95”. May be attached to main cage only at the front and rear section of the rub rail. This means only (2) attachment points are allowed. No open tubing allowed. Tubing must be capped or rounded with no sharp edges. No rub rails are allowed on the rear outside quarter panel area. Rub rails may NOT extend outside of tires.

Windshield Bars:
A minimum of (3) vertical windshield bars are required. Must be a minimum of 3/8” diameter steel and mounted in front of the driver.

Hoosier IMCA stamped G60’s, American Racer KK 704’s or Factory Stock Legal Size Asphalt Pull Offs. (10” max. width for Pull Offs).   Grooving, Grinding and/or Siping of all tires is allowed, but cannot be chemically treated.  Any tire checked on the car must meet a minimum of 51 durometer reading whenever and wherever checked.

Any 8” wide steel wheel is allowed. Any offset from 2” through 5” is allowed. After-market 5/8” lug studs are mandatory. 1” diameter lug nuts are required. Wheel spacers are allowed. Wheel adaptors are not allowed. No screws allowed. A protective outer ring is allowed to be welded to the outer lip of the wheel with a maximum size 1/2” O.D., round or square is allowed. A flat bar of 1.25” may also be used. Bead lock placed on right rear only. Mud Protectors or mud plugs may be used on the right side tires only. (front and rear).

Any oil or transmission fluid coolers in the driver’s compartment must be configured to shield driver in case of leaks. The cooler lines must be encased in tubing, rubber or steel may be used.

Fenders may be cut for tire clearance only and fender must be within 7” of the tire. Front inside fender wells must be removed.

Stock OEM bumpers are required. Option: After-market plastic bumpers may replace stock OEM bumper but must not extend past fender in width. A maximum of 2” X 3” rectangular tubing or 1 ¾” round tubing should be used to support plastic Bumper loops are required to protect radiator, fuel tank and to be used by wrecker for tow hooks. Single horizontal, single hoop bar is the only bar to protrude through the nose. Maximum 1.5” X 0.95”round steel tubing, maximum 8” tall and not wider than the frame horns and mounted to the frame or bumper only. You will be asked to cut them off if wider than frame horns.

Factory Steel roof is mandatory.

Factory Steel Hood and Factory Steel Trunk lid is mandatory. Hood and Trunk may be hulled and must remain in place at all times. Hood and Trunk must be pinned. No holes allowed in hood: therefore, no working hood scoops. Any holes in hood must be covered by .20 guage steel. Quick release hood pins and rear deck pins are required. Hood must make a complete seal at dashboard and/or firewall. The engine compartment must not be visible from driver’s seat.  Enclosure required at rear bumper to trunk lid.  Fuel cell should not be visible.

Not to exceed 6” and must be attached to rear of trunk lid only. May not extend past the width of the car and may not have side-boards. Spoiler supports may not be taller than spoiler and may not be longer than 12”. Spoiler may be made of aluminum, steel, or lexan.

Only (1)- 12-volt battery allowed. Battery and battery box must be securely mounted to car and safely sealed. Battery must be completely encased in an enclosed battery box if mounted in driver compartment.   A master shut-off switch is required and should be mounted in an area behind the driver and visible to the emergency personnel if needed.

Racing seats with rib supports are required. No fiberglass or bucket seats. Seats must be securely mounted to chassis (not floor pan) with a minimum of (4) 3/8” bolts, of which (2) must be mounted in the middle of the seat at the drivers back.

Safety Harness:
Racing type 5-point seatbelts are mandatory. All 5 belts must be fastened while driver is in car and on racing surface. Must be securely mounted with ½” bolts and tabs welded to the cage or frame. Belts must be less than 5 years old.  If the SFI tag is not present or is not legible, the belts will be deemed illegal.

Window Net:
A window net with quick release is required. It may be mesh of ribbon type. Sprint car nets will be allowed but must be accompanied with Arm Restraints.

Numbers must be 24” high and 4” wide on both sides of the car, 24” tall on the roof and positioned so it can be read in the scoring tower.  The number on the roof is the most important. Reflective vinyl is NOT allowed for roof application due to the poor read ability. All numbers should be of different color than background.

Helmets must be Snell 90 or newer and must have Snell sticker clearly visible inside the helmet. Snell ratings of M90, M95, M00, SA90, SA95, and SA00 are legal. If the Snell rating tag is not visible or legible, then the helmet is not approved for racing.

Protective Clothing:
All drivers are required to wear driving suits that are made of fire retardant material that effectively covers the driver’s body, (multi-layer recommended). Neck brace is MANDATORY. Driving gloves and shoes are strongly recommended.

Protest must be made before a feature in writing by driver ONLY!!!!! See RPR tech official.
Valve cover removal and inspection is $75; $50 to the driver and $25 to the track.  Head removal and inspection is $150; $100 to the driver and $50 to the track.  Royal Purple Raceway reserves the right to change or modify a rule that is deemed to be a performance advantage.