358 Sprint Car Rules

 

BOLD & UNDERLINED = NEW RULES FOR 2020

updated 1/9/20


GENERAL - No traction control devices are allowed. No car will be allowed to compete without a top wing or engine body.  


AXLES - Steel front axles only. Rear axles may be aluminum.  


BODYS - Hoods are mandatory. The rib may not extend higher than 2 1/4 inches. 


BRAKES - Must have front and rear brakes in working order. Titanium rotors are allowed. Carbon fiber brake rotors are not allowed.  


BUMPERS - Nerf bars and Bumpers are mandatory and must be made of steel at least one-inch in diameter and bolted or roll pinned to the vehicle, no pop rivets.  


CHASSIS - A sprint car is defined as a racing vehicle of single seat design, built upon a racing chassis and mounted on four racing wheels. No rear engine or aluminum frames allowed. No box tubing frame rails. Driver's compartment shall be separate from the engine by a firewall of suitable material.  


COMBUSTION CHAMBER - Grinding in the combustion chamber will be permitted. Welding in the combustion chamber will be permitted for repair purposes only. No welding to reshape the combustion chamber. The combustion chamber will be defined as beginning with the head gasket area and ending at the top of the valve seat. This is to allow the participant to meet the 10.80 to 1 compression limit and allow competitor valve 
jobs to be performed to meet specifications outlined in intake and exhaust specifications. 

 

CYLINDER HEADS - Cast iron heads of stock configuration mandatory. Stock valve guide angle, no relocating valve guides, example GM-23 degrees. No raised intake runners or spread port exhaust. Porting into runner 3/4 inch to match manifolds allowed. Port and polish OPTIONAL. No modification allowed to heads that would allow the use of down nozzles or multiple spark plugs per cylinder.  


DRIVELINE – Titanium drivelines are allowed. No carbon fiber. 


ENGINE - Titanium or carbon fiber will not be permitted except where listed elsewhere. Cast iron production blocks are mandatory. GM steel heads must have 23 degree valve angle. Engine size 358 cubic inch maximum displacement. Flat top pistons only, no domes or dishes and top of piston square to the bore of the cylinder. Zero deck height. Maximum compression ratio of 10.80:1. Maximum 3.5 inch stroke. Weight of crankshaft is not to be less than 46 pounds. No V-6 engines. No titanium, plastic or carbon fiber components for crank or rods. 


EXHAUST - Exhaust port may be matched to gasket or header, not to exceed a depth of 3/4 inch. Exhaust valve size may not exceed .025 inch over stock size, i.e.: 1.600 stock - 1.625 inch maximum. Exhaust seats may be back cut under valve seat with a maximum angle of 75 degrees. No grinding or acid 
etching under the valve seat will be permitted.  


FLAT TIRES - During the 358 Sprint Feature, any car receiving a flat tire will be given three (3) laps to return to the track. The three (3) laps will be given when the car reaches their pit or safe designated area. If any other part of the car is wrenched on, then the three (3) laps will not be awarded
No car will be permitted to restart with a flat tire.  


FUEL INJECTION -  Must be naturally aspirated. Fuel injection or carburetion allowed. Timed and/or electronic fuel injection units are prohibited,  


FUEL TANKS -  Approved fuel bladder required. No carbon fiber fuel tanks.  


INTAKES -  Intake port may be matched to the intake manifold or gasket, not to exceed a depth of 3/4 inches. Intake valve may not exceed .060 inch over stock valve size, i.e.: 2.020" stock - 2.080" maximum. Intake seats may be cut back under the valve seat with a maximum angle of 75 degrees. No grinding 
or acid etching under the valve seat will be permitted 


PUSH OFFS – There may be more than one after initial push off. 


SHOCKS -  No cockpit adjustable shocks or weight jacks. Drag Link must be tethered to the frame with nylon webbing of at least 1 inch width. 

 

TIRES - All 4 tires must be Hoosier brand tires. You must abide by this rule after drivers first visit for the season. 


Front Tires - Part #31-131 85/8.0-15 D12, Part #31-132 85/8.0-15 D15, D20 - Same as current front tires. 


Left Rear Tires - Part #38-137 15.0/90-15 H12, Part #38-147 15.0/92-15 H12, H15, Part #38-157 15.0/94-15 (SH) H12 


*94” left will be offered in a short and tall* - Part #38-159 15.0/94-15 H12, H15, Part #38-167 15.0/96-15 H12, H15  


Right Rear Tires - Part #38-221 105/16.0-15 H15, H20, Medium, *the 105/16-15 right rear can be utilized on current 16”, 17”and18” wide wheels. *Factory development on the 105/16-15 has been conducted on a 17” wide wheel so the recommended wheel width is 17”. 

* The minimum recommend width is 16” and maximum is 18”.- Part #38-231 105/18.0-15 Hard (Emergency Tire)  


VALVES - Titanium or carbon fiber valves and valve spring retainers are allowed, solid titanium drive shafts. 


WHEELBASE - Allowable wheelbase of 85 to 90 inches.  


WEIGHT - Total weight of car and driver may not be less than 1500 pounds at any time. Weight to be measured as car comes off of the track in the condition that it took the checkered flag. No bolt on weight. Weight measured by speedway scale in the center of the pit area.  


WINGS  - For the 2020 racing season, 358 sprint cars may use either the previously standard 3’x5’ top wing OR a 5’x5’ top wing as currently used on 410 sprint cars. However, if a 5’x5’ top wing is used on a 358, it must conform to all 410 top wing specifications but the wickerbill height cannot exceed one inch. 

 

TOP WINGS - Center foil maximum size of 25 square feet with a maximum width of 60 inches. Center foil must be square or rectangular in shape with all 4 corners set at 90 degree angles with no variance allowed. Center foil top is to be flat from front to back and side to side. Maximum 1” removable wickerbill may be mounted on the rear edge of the center foil. Wickerbill must be 90 degrees to the top of the center foil. No built-in wickerbills or gurney lips allowed. Maximum dimension of wickerbill may change periodically. 


Maximum 1” removable wickerbill may be mounted on the rear edge of the center foil. Wickerbill must be 90 degrees to the top of the center foil. No built-in wickerbills or gurney lips allowed. Maximum dimension of wickerbill may change periodically.  

 

358 teams must use the same wing size for the duration of an event (heat or feature). A wing size change during an event will result in the car starting in the rear of the field. A wing size change between a qualifying event and feature maybe done without penalty. 

 

Front wings - Maximum size to be six (6) square feet total with a maximum width of 36 inches. Center foil must be square or rectangle in shape with all four corners of foil 90 degrees.  Side panels maximum size 12"x 26" with a maximum of a 1/2 inch turnout at a 90 degree from panel. A 1-inch wicker bill is permitted. 


All wings must be fabricated of metal alloys only, no fiberglass, plastic or carbon fiber, except for a 6 inch cover on leading edge of center foil. Center foil must be one (1) piece. Side panel must be one (1) piece. No split wings or bi-wings.  


Side wings, rear wings or rudders are not allowed.  


The top wing can be cockpit/driver adjustable. Other than the slider mechanism, no moving parts permitted on or in foil structure. Only one slider mechanism allowed on top wing, allowing adjustment forward and backwards only.