Pure Stocks



1.    Any American manufactured front or rear wheel driven vehicle with a minimum stock wheelbase of 101”.  No convertibles or station wagons.  Must be street production model.  No high performance cars or options of any kind.

2.    For driver safety, all cars must have a minimum four (4) point roll cage in the driver’s compartment.   Roll cage must be welded to frame rails and all connections must be fully welded.  All cages must be constructed of black iron pipe or seamless black tubing with a minimum outside diameter of 1.5” and a minimum thickness of .083.  No exhaust, galvanized, or aluminum pipe allowed.  There must be four (4) vertical bars welded to the frame inside the driver’s compartment.  A rear hoop behind the driver’s head welded to the rear vertical bars is required.  A front hoop following the contour of the front windshield post and the top of the windshield welded to the front two vertical bars is required.  Front and rear hoop bars must be connected with two (2) horizontal bars at the top of each door.  A minimum of four (4) horizontal bars are required in the driver’s side door and a minimum of three (3) horizontal bars are required in the passenger’s side door.  A radiator support bar may be run from the roll cage through the front firewall and around the front for radiator support only.  A radiator support bar may be installed ahead of the radiator between the two frame horns.  A maximum of two (2) vertical bars may be installed behind the grill between radiator support bar and horizontal loop bar inside frame horns for the purpose of protecting the radiator. Support bars can be installed from top of main cage through rear firewall down to rear frame rails only inside of trunk.  A rear loop bar to protect the fuel cell may be installed by welding to the support bars inside of trunk.  All roll bar installation and workmanship must be approved by the track officials.

3.    Cars must be strictly stock.  Complete bumper to bumper steel unibody must be retained.  No cutting, chopping, channeling or shortening allowed. The only inner body panels that may be removed are the roof and both doors to allow for roll cage installation.  All other inner body panels must remain intact.  All doors must be welded shut.  The steel stock unaltered floor pan, fire walls, trunk (except where fuel cell is located).  Front fender wells may be removed.  Dashboards are required, but may be replaced by steel or aluminum.  All front and rear firewall holes must be sealed off with steel sheet metal to fully enclose the driver’s compartment.  Rear seat shelf must remain intact or replaced with stock appearing steel sheet metal. No aluminum allowed (except in dashboard replacement).  No holes in the hood.  Hood pins may be installed.  Trimming of wheel wells allowed for tire clearance (2” maximum).

4.    No push bars or trailer hitches allowed.  Front and rear bumper brackets and mounts must be welded solid. Bumpers must have four (4) pieces of 5/16” minimum log chain or steel cable going around or through the bumper and through the frame snout to secure bumper.  Drivers who lose their bumper will be sent to the pit area.  Wrecker hook-ups are required on the front and rear of the car.

5.    Racing fuel cells (maximum 22 gallons) are required and must be mounted inside of the trunk area inside of a steel sheet metal container and cannot hang lower than frame rails (see illustration at the back of the book).  No altering or removal of trunk floor except for fuel cell installation and the area must be sealed off with steel sheet metal.  Fuel line must be enclosed in steel tubing and run through the driver’s compartment following the contour of the floor pan.

6.    Battery must be located under the hood or in the driver’s compartment.  If in the driver’s compartment, the battery must be enclosed and securely mounted.

7.    The only aftermarket gauges that are allowed are a tachometer, oil pressure gauge and a water temperature gauge.  All other gauges must be disconnected.

8.    All glass must be removed.  Windshield must be removed.  Heavy screen and/or bars must be installed to protect the driver.  All of the glass, trim, headlights and chrome must be removed.



1.    No modifications to the suspension is allowed.  This means NONE.

2.    Suspension parts must remain absolutely stock for that make and model car.  Unitized frame maybe connected together to complete full frame. Except for front spring allowances noted in suspension rules below.  No spacers, lumber, chains, etc. may be used to alter the stock suspension of that car (even if the factory installed it).  Stock or stock replacement shocks only.  No air shocks, load levelers or racing shocks allowed (even if the factory installed them).  All rear springs must be stock and unaltered.  Rear springs must be the same height/same length, same wire/bar size.  No modifications to the rear springs are allowed.  All front springs must match (left and right) exactly.  Front springs must be the same height, wire size and spring rate.  Height of the springs must be within one inch of the factory stock dimensions for that make and model car.  Spring rates may be checked to be equal.


1.    Only standard rain tread DOT tires will be allowed for competition.  Maximum size is 255-60.  High performance, soft compound, directional tires will not be permitted.  Tires softeners and heaters will not be allowed.  Minimum durometer reading is 65 (the track durometer is the official durometer).  Tires may be impounded by OSP officials and checked.  The BF Goodrich T/A Radial is a track approved tire.  Tire manufacturers markings may not be ground off tire.  No grooving or siping allowed.

2.    Any steel wheel that is 7″ or 8″ wide is allowed.  Larger wheel studs and lug nuts are recommended for safety.  No quick change studs allowed.  Right front wheel MUST be reinforced to prevent loss during competition by either plating, washers, double nuts or larger nuts.

3.    All four wheels must be the same diameter and offset.


1.    THE ENGINE MUST BE STRICTLY STOCK FOR THAT MAKE OF CAR and in its original mounts.  No high-performance engines allowed.  The only legal engine sizes from each manufacturer and the engine specifications are listed in these rules.

a.    Engine sizes are interchangeable within manufacturer’s lines.  Engine parts are not interchangeable between different size engines.

b.    With this new rule change in 2008, the competition will be evaluated weekly by OSP Officials to determine if a weight change is in order to keep parity among the different size engine/cars.

c.    General Motors produced 305 c.i. engines will be allowed to run in any GM make car that came stock with a 305 c.i. Buick, Oldsmobile or Pontiac engine at the time of production.

2.    Engine may be .040 over bore plus wear.  Cast OEM replacement pistons only.  No performance or lightweight pistons allowed.  Only factory stock intakes and exhaust manifolds are allowed.  May use Hedman Block Hugger Headers, Part #68390.  No porting, polishing or grinding of any kind allowed.  Repaired engine parts must be removed.


305 GM          Dish Piston                                      .000 deck clearance

            1.94 intake    1.50 exhaust                        58cc minimum


305GM           Flat Top w/4 valve reliefs             .020 deck clearance

                     1.94 intake    1.50 exhaust                        58cc minimum


350 GM          Dish Piston w/4 valve reliefs       .000 deck clearance

                      1.94 intake    1.50 exhaust                        72cc minimum


350 GM          Flat Top w/4 valve relief                .020 deck clearance

                      1.94 intake    1.50 exhaust                        72cc minimum


318 Mopar    Flat Top                                            .050 deck clearance

                                1.78 intake    1.60 exhaust                        62cc minimum


340 Mopar    Flat Top                                            .050 deck clearance

                     1.88 intake    1.60 exhaust                        70cc minimum


360 Mopar    Flat Top                                            .050 deck clearance

                                1.88 intake    1.60 exhaust                        70cc minimum


302 Ford       Dish Piston                                      .000 deck clearance

                                 1.84 intake    1.48 exhaust                        62cc minimum


351 Ford       Dish Piston                                      .000 deck clearance

                                 1.84 intake    1.48 exhaust                        62cc minimum


3.    Factory balancing only.  No grinding or balancing of pistons, rods or crankshaft allowed.  Oil holes can be chamfered.

4.    No high performance heads allowed.  Stock valve jobs only.  No angle valve jobs allowed.  Oil shedders may be discarded.  Steel or bronze valve guides may be used.  Rocker arms studs may be pinned.

5.    No grinding, altering or removal of any casting numbers, marks or part numbers on any part of the engine, heads or manifolds is allowed.

6.     Ignition system must be OEM stock.  Coil, modules, etc. must be stock or OEM replacement.

7.    Carburetor must be stock or OEM replacement.  Removal of choke butterflies is allowed.  No other modifications to the carburetor are allowed.  No adapters or spacers allowed.  Double spring return is recommended.  Fuel injection models may use track approved OEM carburetors and intake to replace fuel injection system.  Fuel injected allowed but must be stock for make and model.  No modifications allowed to the fuel injection system. . Optional Carburetor Model 4160 – List 1850 600cfm single line, must have choke horn and list number. May remove butterflies and change jets. Adapter plate only no spacer. $300.00 claim on carburetor.

8.    Stock timing chain only.  No buttons or multiple key ways.  Double roller is allowed.

9.    Any hydraulic camshaft with a maximum lift .480. Rocker arms 1.5 ratio stamped steel only, long slot ok. No roller tips or rollers. Stock or OEM replacement lifters only. No anti pump ups, solid, roller, mushroom cams or lifters allowed.  No cross fire cams.    

10.Optional engine equipment – valve covers, air cleaner, engine fan, oil pan and radiator only.  External mounted Ford starter solenoid is allowed. 

11.Any parts not mentioned above must remain stock or OEM replacement.



1.    Any driver finishing within three positions of an opposing driver and on the lead lap may claim that driver’s engine for $750 in cash or certified check and exchange of their engine.  The engines must be the same (i.e. Chevy for Chevy).

a. The engine claim includes the following parts:  Block (all parts internally), heads (all parts internally), intake manifold, exhaust manifold, water pump, harmonic balancer, pulleys, oil pan and motor mounts.

2.    Refusal to accept the claim will result in immediate disqualification, loss of points and prize money from that event. 

3.    A driver must have competed at the track the previous three race events to be eligible to claim another driver’s engine.

4.     The Chief Steward has the right to refuse any claim.  OSP will not allow anyone to abuse the claim rule.



1.    Stock unaltered automatic transmissions only.  All forward and reverse gears must be operational.  Stock coolers allowed under the hood.

2.    Stock rear end with any gear ratio.  Welding of the spider gears is allowed.  No positive traction allowed.




 1. Minimum weight for all cars 3400 pounds with driver after Heat and Feature. Weight must be displayed on top of right front fender.


a.    One 4” round mirror is allowed to be mounted on the interior driver’s side door.

b.    No two-way radios or electronic communications allowed.

c.    All Pure Stock drivers must use a “Raceceiver”.  This will allow the control tower officials to communicate with each driver.  The “Raceceiver” is available for purchase from OSP.

d.   Any car visiting from another track may run with weight penalties. Driver must speak with tech man before racing to assess weight penalties or car will be disqualified. 50 pound penalty per item.