Junior Sprint Format (Sunday-Friday)

• Pill Draw for Heats

• 8 or 10 lap distance for heats (10 Minute Time limit can be enforced any time)

• Heads up line up for Feature

• Feature will be 15 or 20 laps

• A driver who goes two laps down during the course of an event (heat, qualifer, B main, A AMain) will be removed from the speedway for the remainder of that heat race.

Junior Sprint Format (Saturday Finale)

• Pill draw for timed warm up order

• Timed hot laps to determine staring position

• Invert of four for heat races

• Points from Timed Hot laps and Heats determines feature line up

A time limit may be enforced by 600 Speedweek officials at any point during the night of competition in order to combat elements of the race night to complete the event. Example: Curfew, weather delays, etc.

Junior Sprint Rules

1.Frame Construction

● Minimum 1” O.D. x .065” wall 4130 condition N tubing or 1” x.083” Mild Steel on main rollcage tubing and uprights as well as bottom rail.

● 6 point minimum vertical uprights to support top roll cage.

● All 4 corners of the top roll cage must be gusseted with 3” minimum gussets 5/8” OD x.065tubing.

● No slip joints allowed anywhere on the frame.

2. Head Clearance & Halo

● A minimum 3” from the top of the drivers helmet to the top of the roll cage, when seated innormal driving position, directly above the head.

● If the clearance is less than specified, a 3 or more point halo (bolted clamped or welded in)must be used to provide proper head clearance.

3. Seat

A full containment seat is highly recommended. If a full containment seat is not used, vertical or horizontal side frame frame bars on the left and right side to protect the driver are mandatory.

● Head supports on the seat should be the same height as the driver's ears.

● Use seat manufacturer recommended sizing to be sure the seat is properly fitted to the driverat the waist, hips, shoulders, and head.

● A quantity of (4) 5/16” bolts must be used to securely mount the seat.

● Large diameter (fender) washers must be used if the material thickness of the seat at

mounting area material is less than .090”

● Seat can not be mounted such that it protrudes below the bottom rail.

4. Seat Belts

● See supplemental SFI Seatbelt Mounting Installation document for proper seatbelt

mounting methods.

● Five point belts, lap belts, shoulder belts and crotch belt are mandatory. Six point belts areoptional. Minimum 5/16” bolts or proper wrap around (not on bottom rail) mounting required.

● Lap Belt Angle: 45° to 80° from the horizontal.

● All shoulder harnesses must be mounted so that straps loop over a bar. This bar must providethe shoulder belts with a 0” to 2-1⁄2” above the perpendicular line of the drivers chestline to top

of shoulders.

● Seat cutouts for shoulder belts and shoulder belt bar must be located such that they do

not contact the seat.

● No sharp edges on the seat for any belt cut outs.

Body

● Full sprint car type body must be used.

● Sprint car look tails must be in place.

● Chain Guards .060” aluminum chain guards or a full arm guard must be installed where chains are exposed to the driver. Driver must not be able to touch the chain while in race

seating.

● Firewall between the driver and the engine compartment is mandatory. Minimum

thickness is .050” aluminum.

● Quick release steering wheels are highly recommended.

● Any body panel may not extend past the body surface more than 2-1⁄4”. This includes rear sailpanels.

Cockpit

● No cockpit driver adjusters of any kind allowed.

● Kill switch (ignition switch) and starter button must be on the dash and able to be accessed by the driver.

● NO crew-to-driver radio communication Fuel

● Methanol Alcohol fuel only. No Gasoline.

● Top end lube is legal.

● No performance enhancing additives in fuel or top end lube.

● A maximum of 2 gallons of fuel may be used.

● VP M3 and M5 and other brands of like fuel are illegal. Any approved test means available may be used.

Bumpers and Nerf Bars

● Front & rear bumpers, right & left nerf bars are mandatory.

● Nerf bars can not exceed past the outside oF the rear tires by more than 2” and must be nomore than 4” inside of the rear tires.

● All bumper ends must be bolted to the chassis. No rivets or pins of anytype may be used.

● Front bumper can not extend past the frame by more than 8”.

● The car must start the race with all bumpers intact. It may finish the race without a front

bumper, but nerfs and rear bumper must be on the car to race (one leg of 3 point or 2 legs of a 4 point nerf may be cut off in hot pits if necessary to keep racing).

Brakes

● All cars must be equipped with properly functioning rear brakes capable of locking up

the rear tires. Front brakes are not mandatory.

Driver Safety Equipment

● Helmets must be one piece full faced and Snell rated not to exceed three prior “Snell

years” evaluated Jan. 1 of that race season. No damaged or cracked helmets.

● Full SFI-3.2A/5 rated driving suits are mandatory

● Arm restraints and gloves are mandatory

● Neck collars or head & neck systems are mandatory and are to be worn according to

the manufacturer's recommendations.

Wheels

● Only 8” diameter wheels can be used. Tires

● Right Rear tire must be a Hoosier 16.0/8.5/8/8 RD 20.

● Mechanically modifying the tire is ok (groving).

● Chemically treating the tire in any form is illegal.

Weight

● 400 pounds minimum car and driver after the race.

● Added Weight: Any material used for the purpose of making the weight limit must be welded or securely bolted to the car frame. No liquid or loose ballast will be permitted. The weight must not be able to move during the race.

Wings

● Right side board, maximum 42" x 20" - 16” x 16” minimum.

● Left side board, maximum 42" x 20" - 18” x 18” minimum.

● Side boards may not extend more than 3" beyond center section and sides must cover center section.

● Overall wing size minimum 5.5 square feet minimum.

● Cannot be mounted outside the centerline of the tires.

● The side board kick out cannot exceed 2 inches.

● Nose wings are optional and cannot exceed 24"x 18". Sideboards not to exceed 8.5” tall

and 21” long

Engine

● Briggs & Stratton World Formula engine

● All parts must be B&S factory production parts unless otherwise noted in these rules. No

machining or alteration of parts is permitted unless specifically noted in these rules. All parts are subject to comparison with a known stock part.

● DO NOT ASSUME ANY ITEM IS LEGAL BECAUSE SPECIFIC REFERENCE IS NOT

MADE

● Shroud and covers: All shrouds and covers must be run as supplied. Flywheel cover, top

plate are non tech items. Cylinder shield may be trimmed for CHT sensor installation and

header flange clearance. Bolts used to secure metal or plastic covers may be replaced with

larger diameter bolts. Breather by- pass (555688) is allowed.

● Exhaust: RLV 5442S only (coated or non-coated allowed). Header may be cut and turned to fit car as long as the overall length and tube size remains the same as stock factor header: 20.5” .9375” x .065” wall (.807 +/-.005 Any exhaust gasket or you may use sealer. Exhaust gas temp sensor is allowed. RLV Silencer #4100 Required and may be coated.

● Air cleaner: B&S #698973 Green air filter brand 40 x 75. Pre-filter may be used.

● Engine must be self starting using a minimum 8 AH battery capable of starting a warm engine must be used.

● Fuel pump must be B&S part 557033. Must be pulsed from intake manifold only

● Clutch: May be engine and\or Jackshaft mounted. Belt or chain drive from engine to

jackshaft. May use #219 or #35 sprocket. NO VARIABLE SPEED CLUTCHES, CVT, SNOW MOBILE, JR DRAGSTER OR VARIABLE GEAR RATIO DEVICES OF ANY KIND ALLOWED.

● Rev Limiter: Rev limit is 7100 rpm +/- 100 rpm. May be checked at any point in race

program. Rev limit will be checked with a suitable memory capable tachometer attached to the plug lead and motor accelerated until the rev limiter begins to function. All rev limiters must function within 100 rpm when checked with the same instrument.

● Oil: Any crankcase oil is allowed BUT MUST PASS THE BURN TEST AND/OR THE

SNIFFER TEST. (Recommend TIFF Industries Sniffer)

● Carburetor, Spacer, Manifold: Stock Walbro PZ carburetor only. No alterations allowed; choke excluded. Carb mount boot Briggs #557130 is required. Unaltered intake manifold and pulse line only Briggs #557009. Slide must remain unaltered. Unaltered Stock needle marked CDB is required. Choke assembly is optional and may be removed and shaft holes plugged with silicone. If choke is retained choke lever may be fastened open with spring, rubber band or tie wrap.

Methanol Jets: Drilling or reaming of gas carb jets is allowed. Venturi measurement, Vertical .9902” max Horizontal .7382” max

● Check ignition timing with the right edge of the magnet (not the magnet holder) aligned

with the right edge of the notch on the bottom of the right leg of the coil. The degree

wheel must indicate between 23 and 29 degrees BTDC. Flywheel key must have BS logo.

Minimum key width is .182 inch.

● Deck/Piston Clearance: Machining of deck surface is permitted. There will be no knife

edge finishes allowed, smooth finish only. Piston pop up cannot exceed .035” above block

surface in the center of the piston. When measuring piston pop up, use the backside of the Sox pushrod gauge or set flat bar stock across piston parallel to wrist pin. Use dial indicator to check pop up on center of this bar. Carbon may be removed from the top of the piston prior to measuring. Top of piston may be filed to relieve protrusions left by number stamp on top of piston.

● Bore: Maximum bore 2.725”. Factory oversize pistons allowed.

● Stroke: Maximum stroke is 2.204”.

● Head gasket: Any commercially available head gasket may be used but must maintain the

same configuration of shape of standard Briggs World Formula gasket. Minimum thickness is .040 measured with a micrometer from inside the cylinder hole of the gasket at 4 points between the head bolts. Fire Ring, B&S gasket is legal.

● Head: Head may not be altered in any way from factory specifications. NO PORTING

OF ANY SHAPE OR WAY! Heat sink P\N 555690 is allowed. Cylinder head gasket

surface may be machined. Depth from gasket surface to head surface between

valves must be a minimum of .319”. Measure by using a depth micrometer. No knife edges

or angle milling of head. Cylinder head must be as furnished from Briggs. No polishing,

grinding or machining of valve seat angles, or intake and exhaust runners allowed. 45 degree

Valve Face and Seat angle and width as factory supplied.

● Rocker Arms / Push Rods: rocker arms must be as produced. Length must be 2.820

inches minimum. Push rod length 5.638" no go to 5.656 must go. Push rod diameter is

.185 to .190".

Specification for Engines:

● Intake Port: No media blasting of any type allowed on intake port in\on the head or manifold.

Must be as cast. Maximum diagonal measurement is 1.101”. Maximum vertical measurement is 1.044”.

● Exhaust Port: No media blasting of any type allowed on exhaust port. Must be as cast.

Maximum I.D. of shoulder in bottom of exhaust port is .854”

● Valve Seats: One 45° angle only. Intake valve seat diameter is .966” - .972”. Exhaust valve seat diameter is .844” - .850”.

● Valves: Intake valve head diameter is 1.055” - 1.065”. Exhaust valve head diameter is

.935” - .945”. Valve stem diameter is .232” -.238”. Valve face must have one 45° sealing

surface only.

● Valve springs: Dual valve springs as supplied by factory are required.Inner spring wire

diameter is .066” - .068”. Outer spring wire diameter is .112” - .114”.

● Valve Guides: Replacement of valve guides with B&S factory part 555645, is allowed.

● Ignition: Unaltered B&S stock coil #557040 w\External Limiter or #557125 with Internal

RPM Limiter is mandatory. Attachment bolts or bolt holes may not be altered.

● Spark plug: Any commercially available, 10mm thread spark plug allowed. Spark plug must be stock. Indexing washers allowed. If using temp sensor you may remove sealing washer.

● Spark plug Connector must be stock factory type. Rubber plug boot is allowed. There must be resistance from plug wire to ground on coil #557040. Resistance must be between 3000 ohms, minimum, to 6000 ohms, maximum. Coil resistance may be rechecked after a minimum of 10 minutes if correct reading is not attained upon first check. No spec available on P\N #557125.

● Coil air gap is non tech.

● Flywheel: Only stock Cast Iron or Cast Aluminum Briggs #557126 flywheel is permitted.

Starter ring gear and all cooling fins must be in place. No machining, glass beading,

sandblasting, painting or coating of flywheel is allowed. Minimum Flywheel Weight with starter ring, cooling fins, and attachment bolts 4 pounds 3 oz. Chipped fins due to poor casting are legal. Completely broken off fins are not allowed. Minimum 1.750 inch Flywheel cover opening allowed. Stock flywheel key with B & S logo is required and will determine Aluminum flywheel ignition timing. The flywheel key may be aluminum or steel. .182 minimum width. NO offset keys permitted.

● One or two stock crankcase gaskets are required.

● Valve Lifters: Must be stock. No Polishing allowed.

● Lifter Heads: Diameter must be .964” - .984”.

● Connecting Rod: Stock B&S part #557005 or 557117 rod only. Rod may not be altered

or polished. Rod may be clearanced providing that it is in stock configuration and

finish, with no dimpling or media blasting. Rod ends must be concentric with crank journal and wrist pin with no chamfer or breaking of edges. Rod length, measured from bottom of wrist pin hole to top of crank journal hole, is 2.419” minimum to 2.429” maximum. Oil Hole Opening: Oil hole opening is .185” no-go. Crank end of oil hole is chamfered.

● Wrist pin: Maximum I.D. is .414”. O.D. is .624”-626”. Minimum length is 1.901”.

● Piston rings: Three rings mandatory. Top compression ring must have chamfer or O

toward top of piston. Second scraper ring must be installed with inside chamfer down and O toward top of piston. Oil ring must be installed as from factory. No alteration of rings allowed except end gapping and lapping. Maximum RING GAP of Rings .050. Rings must be self-supported in the cylinder bore of the engine being inspected. Rings must remain flat. Rings must be in one piece when removed from block. Aftermarket rings are allowed if they meet the Specifications listed below. Minimum width of top two rings is .095”. Thickness of top two rings is .059” - .064”. Minimum width of oil ring is .065”. Ring groove must be present. Expander must be installed but may be trimmed in overall length. Thickness of oil ring is .098” - .102”.

● Piston: Stock “kidney bean” piston required. No alteration, polishing or machining

allowed. Only piston skirts are coated and coating cannot be removed and skirts or any part of piston be polished. Factory finish only. Minimum from top of piston to top of wrist pin on circlip side is .658”. Minimum piston length is 1.768”. Factory oversize World Formula pistons are allowed.

● Crankshaft: Stock B&S crankshaft casting #772 and #052 only allowed, all finishes

being as factory supplied, with stock timing gear installed in stock location only. No

alteration or polishing in any manner allowed. Offset crankshafts not permitted. Stock bearings required. Side cover may be peened to retain side cover bearing. Shim(s) if used, must be installed as from factory Crankshaft journal diameter is 1.094” -1.100”.

● Block: Must be stock with no alterations, except blocks may be repaired from broken

rod damage, providing that repair does not constitute a functional modification of original block.

No welding is permitted from the cooling fins upward.

● Checking camshaft at pushrods: Push gently down on dial indicator stem to ensure that there is no lash when pushrods are going down. Exhaust Lobe Lift Intake Lobe

75-71 BBDC .020 34-30 BTDC

57-53 BBDC .050 18-14 BTDC

39-35 BBDC .100 2BTDC-2ATDC

25-21 BBDC .150 13-17 ATDC

9-5 BBDC .200 29-33 ATDC

12-16 ABDC .250 49-53 ATDC

25-29 ABDC .275 63-67 ATDC

.3085 MAX .3085 MAX

70-66 BTDC .275 31-28 BBDC

57-53 BTDC .250 18-14 BBDC

37-33 BTDC .200 2-6 ABDC

21-17 BTDC .150 18-22 ABDC

6-2 BTDC .100 33-37 ABDC

11-15 ATDC .050 49-53 ABDC

29-33 ATDC .020 66-70 ABDC