Irwindale Speedway Introduces “Street Stock” Division for 2021

Printable 2021 Street Stock Rules

2021 Irwindale Speedway Street Stock Rules

These rules are in effect as of February 15, 2021. This publication supersedes all previous Irwindale Speedway rules and rule updates. Irwindale Speedway reserves the right to alter or amend the rules and regulations in the interest of safety, cost control, and/or fair competition at any time. It is the responsibility of each competitor to read and understand the contents of these rules. If there is a disagreement or dispute regarding the meaning or application of these rules, the decision of the Irwindale Speedway Competition Director shall prevail.

No expressed or implied warranty of safety shall result from publications of or compliance with these rules and/or regulations. The rules and/or regulations set forth herein are designed to provide for the orderly conduct of Irwindale Speedway racing events and to establish minimum acceptable requirements for such events.

No part is deemed to have been approved by Competition Director by passing through prior technical inspections. These rules are intended as a guide for the conduct of the sport and are in no way a guarantee against injury or death to a participant, spectator or official. All participants, guest and crew members fully understand that racing is inherently dangerous and that they are exposed to risks of death or serious bodily injury. The participants, guest and crew members voluntarily assume these risks.

Any questions regarding rules please e-mail:


A. Any 1968 or newer sedan. No Station Wagons, Convertibles, Jeeps, etc.
B. All cars must maintain stock OEM type body. Door panels and rear quarter panels, may be fabricated of steel. Body sheet metal may be updated through current models, but must exactly replace early sheet metal. No interchanging of MFG bodies and frames. FiveStar and AR street stock bodies allowed and mounted correctly per manufacture specs.
C. Original bodylines must be maintained, and stock appearing on fabricated panels.
D. Hood and deck lid pins required. A minimum of 4 pins across front hood, and 2 across rear of deck lid.
E. Full stock floorboards and firewalls required. All holes to be covered by sheet metal and welded in place. Firewall sheet metal must remain in stock location.
F. All doors must be bolted, strapped or welded shut.
G. Rear trunk area may remain open.
H. Rear deck lid spoiler allowed maximum 4” tall and no wider than car or over 60” wide top 3” must be clear plastic.
I. Air scoop for radiator allowed, no wider than radiator.
J. A minimum of four (4) inches of clearance, body to ground.
K. Fiberglass front ends allowed.


A. Full NASCAR type roll cages mandatory. Bars must be a minimum of 1 1/2” O.D. / .090” wall thickness, gusset as necessary for strength.
B. Minimum of three (3) door bars required on both sides. Right side can be straight.
C. Engine must be in stock location.
D. Rear kick bars may extend to rear cross member.
E. Fuel cell protector required, no more than the width of the frame rails.
F. Main roll cage uprights must be fastened to floor of uni-body cars with a minimum 3/16” thick plate, top and bottom, at all four corners. Plate must be a minimum of 4” square, with (4); 3/8” grade 8 bolts at each location.
G. Roll bar padding must be used at any point where driver may make contact.
H. Door bars must be covered with a 1/16” thick steel metal plate, top to bottom, from front and rear uprights, welded to outside of bars.
I. A radiator protector/front hoop, 2/3 the height of the uprights of the roll cage, but must follow the frame rails. 1 1⁄2” O.D. maximum.
J. Stock frames only. No modifications allowed.
K. Oil pans must have a minimum of three (3) inches of clearance.


A. A windshield made of LEXAN may be used. Minimum thickness is 1/8 inch. Windshields must be supported between the dash bar and the roof halo bar with a minimum of two (2) evenly placed metal straps 1/8 inch by 1 inch or a single 1.75 inch bar in the center of the windshield welded to the dash bar and the roof halo bar.
B. Each car may have a rear window made of clear LEXAN.
C. All side window glass must be removed. A right side window of any type is not permitted. Side quarter windows behind the “B” pillar can be replaced with LEXAN. Driver side window net is required on all cars. Net material must be minimum 1 inch wide and have openings of at least one (1) inch. Net must be equipped with a quick-release device on the top left corner.
D. All mirrors including mount locations subject to specific tech approval.
E. Left side mirrors allowed.


A. Minimum of four (4) inches of ground clearance.
B. Cars with factory wheelbase of 110” and over (Nova’s, Chevelle’s, Monte Carlo) must weigh 3100 lbs with driver.
C. Cars with factory wheelbase of 110” or less (Camaros, Mustangs, and Firebirds, and or similar type cars are allowed) must weigh 3200 lbs with driver.
D. Left side weight with driver cannot be over 54%.
E. No wheelbase can be less than 108” at any time. Any car under 108” is 200# penalty.
F. Any car with front weight jacks must add 50 lbs. Still maintaining 54% left side.


A. Front and rear bumper must be fastened to the fender and or quarter panel.
B. Bumper height must measure 15” to 18” center to ground.


A. Cylinder compression limited to 10.5 to 1 Maximum.

Ford 351 C.I.
Chevrolet 350 C.I.
Dodge 360 C.I.
Plus max .060 overbore

Maximum cubic inch 360cc.

No Big Blocks.

B. Engine oil coolers allowed.
C. Aftermarket oil pans, valve covers, water pump, fan pullies are allowed.
D. No “stroker” or lightweight cranks allowed, factory EOM cranks only.
E. Heads: Stock cast iron heads only. A stock head will be characterized as a cylinder head which was offered as standard equipment with no performance advantage.
F. No special performance options will be allowed, including but not limited to, oversize valves, special cut valves, relocated intake or exhaust bowls or ports.
G. No porting or polishing will be allowed.
H. Vortec heads are allowed.
I. Stock steel, stock stainless steel valve train components only, 1.5 ratio roller rockers allowed. NO shaft rockers.
J. Screw in studs and guide plates allowed.
K. Engine Blocks: Stock cast iron blocks only. No modifications allowed.
L. Stock stroke for engine being used, exp. 350 C.I. Chevy 3.48” stroke.
M. Stock rods only after market rod bolts OK.
N. No roller or mushroom lifters allowed.
O. Stock type timing chain and gears only.
P. No belts or gear drives allowed.
Q. No crank lightening or grinding allowed.
R. No after market lightweight cranks allowed.
A. Holley #4412 or Holley Keith Dorton #80583 Box stock except for the following: 1) Gasket, bowls seal, accelerator pump squirter, power valve, jets, sight plug, choked plate and shaft may be removed.
B. Pure Stocks with 112” wheelbases can run a stock 4 barrel carburetor or Holley 4 barrel #01850.
C. Two (2) carburetor return springs required must be mounted to engine block.
D. Maximum 1.” carburetor adapter allowed.
E. Aluminum intake manifold permitted.
A. No cold air induction allowed, K&N air filters are allowed.
B. No air deflector allowed on front. Air filters only.
C. Top and bottom of air cleaner must be solid and same diameter.
D. Tubes, funnels, or any device which may control the flow of air, will not be permitted inside the air cleaner.
A. Factory stock location. Factory firewall only in stock location. No modifications.
B. Engine oil pan height must not be less than current car ride-height rule.
C. Crankshaft must be centered within one (1) inch of the vehicle’s front tread width.
D. All mounts must be securely bolted and adjusted mounts are not permitted.
E. Minimum clearance between the center of the crankshaft and the ground must 10.5”.
A. Stock type ignition only. No performance aftermarket distributors or magnetos allowed.
a. NO MSD systems allowed. DUI Voltage enhancer allowed.
b. Magnetos, crank trigger, optically triggered or computerized systems are not permitted.
B. All cars must be equipped with a master electrical switch located in the cockpit of the car. The switch must be within reach of the driver and safety crew from the left side of the car.
C. Batteries must be securely mounted within the confines of the body and behind the driver.
D. Batteries must be contained in electrically insulated container. No marine or plastic type boxes allowed.
E. Batteries must be mounted in front of rear axle.
A. All cars must have a functional fan containing a minimum of four (4) blades, and a minimum diameter of fourteen (14) inches or optional electric fan. Free spin or clutch fans are not permitted.
B. Fan shroud mandatory.
F. No fiberglass flex fans.
G. Fan mandatory, bolted on motor, in stock location. Electric fans are permitted.
H. Water overflow catch can unit required. One (1) quart minimum, vented out to windshield, metal or plastic, mounted in engine compartment.
I. No anti-freeze or similar products. This is a finable offense.
J. Water wetter permitted.


A. Stock manifolds are permitted.
B. Headers are permitted. Must be 1 5/8” tube, down and back, chassis style headers only. No over the top, step, 180s, Tri Y’s, cones or pyramids. Only one gasket, maximum .075” thickness, may be used between the cylinder head and header. Header must bolt to head. Exhaust pipes no larger than 3” outside diameter. Two-into-one collectors are allowed.
C. An approved muffler is mandatory, must not exceed 90 db@100 feet.
D. Exhaust must extend past driver’s compartment and turn down.


A. Clutch must be stock type only. Aftermarket master and slave cylinder allowed.
B. No lightweight or racing type disc, pressures plated, or fly wheels allowed.
C. Aluminum flywheels are not permitted. OEM type only.
D. Scatter shields mandatory. No Lightening of flywheel permitted.
E. Stock clutch (10.5”) and flywheel only. Pressure Plate , Flywheel and Disc minimum weight 30#
F. Locked, limited slip, or positive-traction differentials, is permitted.
G. Rear end must be centered in car.
H. Floater type rear ends are permitted.
I. OEM type 3 or 4 speed transmission may be used. No racing transmission – IE Richmond , Jericho etc
J. Automatic transmissions optional, torque converter must be operational, transmission oil cooler required.
K. Ford 9” rear end allowed. Must be mounted exactly as old rear end was removed, may be used in any MFR line.
L. Two (2) driveline straps, 1” x 1/8” required, mounting to be within 6” of the U-Joints are required on rear drive vehicles. Drive shaft must be painted white for on track visibility in the event it should become separated from the car.
M. No aluminum or composite drive shafts.


A. Stock OEM lower control arms only, no crossing OEM lines and no modifications allowed.
B. Upper tubular A-arms allowed. Must be steel one piece, either steel or aluminum cross shaft allowed. No slugs, bearings, or heim joints. Stock OEM upper A-arms allowed. Any OEM factory production type of balljointmay be used. No “Mono Ball” balljoints. Spindles must be stock OEM for make of vehicle being used.
C. Stock upper control arm mounting may be moved for caster/camber.
D. Rated springs are allowed, front and rear.
E. Lowering blocks allowed.
F. All other suspension components must be of original design and origin for the chassis used. No aftermarket look alike parts to widen suspension. Maximum overall width (front or rear) shall not exceed 78” from outside of tire to outside of tire. Front tire width will be measured at the top of the tire sidewall with driver in the car. NO EXCEPTIONS!
G. No aluminum shocks permitted, any type of adjustable, rebuildable, and/or re-valveable type shocks regardless of make or brand, will NOT be allowed on your car. Shocks must be mounted in stock location. No heim joint type mounts allowed.
H. Adjustable spring spacers allowed. Weight jacks allowed with 50 pound weight penalty. Outboard front shock allowed due to weight jack but must still be non-rebuildable and sealed as stated in shock rule Letter “G”.
I. Rear disc brakes allowed. All components must be OEM steel. No aftermarket parts of any type or brand allowed.
J. Stock, 4 wheel hydraulic brakes required, and all must be in good working order.


A. Stock steering components only.
B. Quick release steering wheels are required.
C. Steering column must be collapsible. Two U joints are acceptable.


A. Cars may use Sunoco 110 (track fuel) or Shell 91 octane pump. The chemical composition of the fuel may not be altered by any means. No fuel additives allowed.
B. All cars must be equipped with an approved fuel cell, securely mounted in the trunk area as far forward as possible. Minimum 10” ground clearance.
C. Fuel cell must be mounted with steel framework (1 inch x 1 inch, .065 inch minimum) and must have a vent hose and the hose must have a check valve in the end.
D. Fuel cell must be totally enclosed in an 18 gauge steel box with a 1⁄2 inch drain hole in the lower right rear corner. Ground strap required from fill neck to frame.
E. Maximum fuel capacity – 22 gallons.
F. No electric fuel pumps permitted. Fuel lines may not enter driver’s compartment.
G. All cars must have a minimum of two (2) springs on throttle return cable.


Steel wheels are mandatory, maximum 8” wide with any offset. Tire and wheel must stay inside of fender and quarter panel.

A. Maximum overall width (front or rear) shall not exceed 78” from outside of tire to outside of tire. Front tire width will be measured at the top of the tire sidewall with driver in the car. NO EXCEPTIONS!
B. 5/8” wheel studs required on all four (4) wheels.
C. The use of any bleeder valve is prohibited.
D. Wheel spacers allowed.
E. The track tire is the Hoosier #970. No star tires.
F. You must start the race on the tires you qualify on.


A. For all safety equipment. It will be the sole responsibility of the driver, not Irwindale Speedway, their agents/officials or corporate officers to ensure that his/her safety equipment is correctly installed, maintained, and properly used. Please refer to manufacturer installation and cage guidelines and adhere to them.
B. Aluminum professionally built high back racing seat required. No plastic or fiberglass.
C. Padded headrest required.
D. Seat must be securely bolted to a mount assembly that is an integral part of the roll cage.
E. Seat will not be attached to the floorboard.
F. A five (5) point safety harness, with quick release is mandatory! 3” wide lap belt, 2” or 3” shoulder belts, and a 2” submarine belt. All belts shall be attached to roll cage using minimum 3/8 grade 8 hardware.
G. Safety harnesses/seat belts may be no more than three (3) years old.
H. Helmets; Head and Neck Restraint Devices:
a. Snell SA2010 or SA2015 helmet required.
b. Full face helmets with Lexan face shield recommended.
c. Nomex helmet, skirt, and Nomex covered chinstrap highly recommended.
d. A HANS or Hutchens type head and neck restraint device is recommended.
I. Window net mandatory. Minimum 1” mesh with release at top only. It is required that all window net releases be updated to the quick release type.
J. Fire suit mandatory at all times.
K. Approved racing gloves mandatory. No welding gloves, gardening gloves, etc.
L. Approved racing shoes mandatory.
M. Eye protection is mandatory and must be in proper place at all times.
N. Current test date (2 pound minimum) fire extinguisher to be installed in the car within drivers reach while strapped in. Metal mounts only, no plastic.
O. All cars will be required to have in their pits a minimum of one five pound, Halon or dry chemical fire extinguisher. This is to be visible to tech officials and all crewmembers. All crew members must be made aware of this location, and knowledgeable in the use of the fire extinguisher.
P. Car and driver will be required to make safety rule violations comply prior to racing any event.


A. All cars are to be neatly and brightly painted.
B. Numbers will be a minimum of 22” on the roof and both door panels. Numbers on the roof to face toward scoring tower (flag stand). No aluminum foil type lettering.
C. Numbers assigned to car will be displayed on the top right front of windshield, 4” minimum.
D. Drivers first and last name to be placed above each door, on the roof in 3” letters minimum.
E. Advertising or names on the windshield is not permitted. This will be reserved for a series sponsor.
F. Advertising that is deemed to be unsuitable/offensive, will not be allowed. Decision of Irwindale SpeedwayCompetition Director will be official.
G. Series sponsor decals, if any, must be placed on designated location of car to be eligible for awards. This is to be completed PRIOR to competing in any event.


A. The use of a two-way radio for communication with a spotter and/or pit crew is allowed. Spotter must be on spotter stand with proper identification.


A. No electronic monitoring computer devices capable of storing or transmitting information except tachometers.
B. No digital gauges, timing retard controls or oxygen sensors allowed.
C. No electronic traction control devices allowed.

22. Penalty Weight for Non Conforming Cars

​1- Fiberglass Roof – add 50#

​2- Fiberglass Quarter panels – add 50#

​3- Fabricated Floorboard (not stock) – add 50#

​4- Fabricated Firewall (not stock) – add 50#

​5- Fabricated Rear Clip – add 50#

​6- Fabricated Front Clip (Camaro replacement) – add 50#

​7- Weight Jacks – add 50#

​8- Hydraulic Roller Cam – add 25#