Hobby Stock Rules:
Cars must be a stock street type. American made passenger cars only. Any steel factory style OEM body is permitted, and must have factory trunk, hood, roof, fenders, and quarter panels. Complete bumper-to-bumper steel body must be retained. 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. No after-market bodies, no stock car bodies, no aluminum bodies or body panels. Note: 1981-1988 Performance Bodies street stock Monte Carlo steel body is the only after-market body allowed. 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. Novas allowed. Only metric framed station wagons are permitted with enclosed rear compartment, no other makes or models will be accepted. No Town Cars, Mustang, Camaro/Firebird or Corvette. No commercial vehicles, convertibles or sports cars. Minimum wheel base is 108” per OEM specifications for stock factory production. Allowance to 107.5” for caster adjustment will be allowed at the technical inspection pad. Chevy S-10, Ford Ranger, Dodge Dakota are also allowed.
Firewalls must be complete, from fender to fender, top to bottom with all holes covered with 20ga steel minimum. Floor may be cut to allow firewall clearance for headers and distributor, but area must be closed with 20ga 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 20ga 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 and must fully extend from left rocker panel to right rocker panel.
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 is the only carburetor allowed Choke horn must be attached. Circle track floats may be used. Number must be legible on air horn. No machine work on carburetor. Holley carburetors must be mounted on cast iron 4 barrel intake with an adaptor only. . Carburetor spacer/adapter is allowed, but must not exceed 1-1/4” total thickness including gaskets. No other spacers are allowed. 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. If a 602 crate motor is used, the rules for carb, spacer and gaskets under the crate 602 ruling in the Limited Modified rules apply. Royal Purple Raceway has the option at any time to eliminate the 4 bbl. carb, spacer and gaskets and require all engines in the Hobby Class, including the crate 602, to run the unaltered Holley 4412 along with proper spacer and gaskets as listed above.
OEM cylinder heads only with a minimum 68cc chamber size. 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. No vortec heads. Race cars using GM engines must run 350 heads on 350 engines, and 305 heads on 305 engines. No aluminum heads. No special order heads or factory special order heads. Any open chamber cast iron steel OEM factory production straight plug head is allowed that meets the described requirements. 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 or triple 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 roller tip rocker arms are not allowed. Poly-locks are allowed. Stud girdles are not allowed.
May be in stock location or #1 spark plug can be even with ball-joint or forward. #1 spark plug may not extend behind 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 components 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. No areowing or similar (but different brand) cranks.
Rods must be 5.7” rods only. 3:48” stroke only. 49 lb minimum weight for chevy 350cid No Chevrolet bowtie, Ford SVO or Mopar performance blocks. Stock stroke must be maintained No performance parts. After-market rod bolts may be used. Only OEM replacement style pistons with four (4) equal valve relief are allowed cast or forged. Floating wrist pins are allowed. Flat top pistons with four (4) equal valve relief or dish pistons only, no domed pistons. No total seal type rings are allowed. Maximum cubic inch displacement allowed is 364 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 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 only. No Hemis.
Again: only, Ford, Chevy or Mopar engines are allowed.
Mopar= Chrysler, Plymouth and Dodge. 370 cubic inch maximum.
Ford= Ford and Mercury. 360 cubic inch maximum.
Chevy= Pontiac, Buick, Oldsmobile as long as they are Chevrolet engines. 364 cubic inch maximum.
Stock style rockers arms only, no full rollers, and no roller tips. 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.
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 180 lbs. per cylinder with 5 bumps of gauge.
Optional: The 602 crate motor is optional for Hobby Stocks.
Camshaft and lifters must be hydraulic with a maximum of 450 lift. Measured at the valve. Tech Clarification: In order to maintain a 450 lift on your camshaft, you must not exceed a camshaft lobe of 280 degrees with 1.6 rocker arms, which will measure a 450 lift. Also, a 450 lift cam with 1.5 rockers arms will measure a 450 lift. Be advised that a 450 lift cam with 1.6 rocker arms will measure 480 lift at the valve, which will be deemed illegal. Know what your camshaft and rocker arm combination produces in order to not exceed a 450 lift measured at the valve.
Intake must be cast iron. No high-rise intakes, no marine intakes and no aluminum intakes. No porting, polishing, port matching, acid porting, acid treatments or coatings of any kind.
Most brand, style or size air cleaner are allowed. NO type of RAM air or forced air induction will be allowed. Any valve cover combination allowed.
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 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. It must be in stock location. No cutting of hood for clearance. Aluminum radiator is allowed. Racing radiator cap is allowed.
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 in a steel can 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 required, 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, valved 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.
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. (ex. 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 must be stock OEM 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 any car. Cars must have a minimum of (3) functioning brakes. 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 is 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. OEM suspension parts only. IMCA TUBULAR UPPER CONTROL ARMS WILL BE PERMITTED (steel only and must be IMCA stamped, non-adjustable). No cutting, welding or bending of frame to accommodate suspension changes. Suspension parts must remain absolutely stock for that year, make and model of car. This includes spindles, rotors, upper control arms, 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 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 to be 13”. Rear coil spring must not extend through the stock OEM upper spring bucket. Adjustable 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.
Shocks must be steel OEM replacement shocks. Shocks must be mounted using the OEM stock mounts in the factory installed location. No heims on shocks allowed. No shock adapters.
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 driver’s 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 cannot 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.
A single nerf bar 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 nerf bar. This means only (2) attachment points are allowed. No open tubing allowed. Tubing must be capped or rounded with no sharp edges. No nerf bars are allowed on the rear outside quarter panel area. Nerf bars may NOT extend outside of tires.
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.
60 series D.O.T. radial tires must be able to have road hazard. You may use Hoosier stamped G60 or American Racer KK 704 as an option. Grooved and siped tires are allowed. No softening of tires.
Any 8” width steel wheel. Any offset from 2” through 5” is allowed. After-market 5/8” lug studs are recommended. 1” diameter lug nuts are required. Wheel spacers are not allowed with stock studs. 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.
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 and single hoop bar are the only bars 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 it is wider than frame horns.
Steel hood/trunk required, No aluminum. Hood/trunk may be hulled and must remain in place at all times. Hood must be pinned. No holes allowed in hood: therefore, no working hood scoops. Any holes in hood must be covered by steel. Quick release hood pins and rear deck pins are required. Hood must make a complete seal dashboard and/or firewall. The engine compartment must not be visible from driver’s seat.
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.
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.
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. It must be less than 5 years old. If the SFI tag is not present or is not legible, the belts will be deemed illegal.
A window net with quick release is required. It may be mesh of ribbon type. No sprint car nets.
Numbers must be 24” high and 4” wide on both sides of the car and 24” tall on the roof and positioned so it can be read from the passenger side. Cars must be painted and numbered neatly and to be seen easily by the score keepers. The number on the roof is the most important. Reflective vinyl is NOT recommended for roof application due to the poor read ability. All numbers should be of different color than background.
Helmets must be full face 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.
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.
$75 valve cover removal and inspection or $150 head removal and inspection of which $100 will go to the driver and $50 to the point fund. Rules are subjected to change at any time. Any rule infraction will be addressed and final ruling made by Royal Purple Raceway Tech personnel.