2017 Limited Modified Rules
CAR MUST BE IMCA LEGAL
Rules apply at all times car is on track. Snell-rated SA2000 or SA2005 or SFI 31.1/2005
Helmet required. (Effective January 1, 2008, SA95 helmets are no longer allowed). Roll bar
padding required in driver compartment. SFI-approved full fire suit required. Fire retardant
neck brace, gloves and shoes required. Driver-side window net required, ribbon or mesh style,
and must be mounted so quick release latch is at top front of window. Minimum three-inch
wide SFI-approved five-point safety belt assembly required (Y-type shoulder harness not
allowed), must be mounted securely to roll cage. Kill switch required within easy reach of
driver and emergency personnel, must be clearly marked ‘OFF’ and ‘ON’.
Car numbers must 14 inches or larger. Must be on the top of the car, the back fenders or on the doors.
1978-1987 OEM midsize GM metric full frames only. Minimum wheelbase 107-inches,
maximum 109-inches, both sides. Frame must be full and complete, cannot be widened,
narrowed, shortened, lengthened, or be cut, bent, or altered to change suspension brackets,
except upper control arm brackets on front end. All frame bolt holes must remain in OEM
location. Front frame horns may be removed in front of steering box. Front frame may be cut
for radiator clearance. Frame may be notched for seat clearance. Transmission crossmember
mounts may be removed, no further forward than frame welds. Rear of frame, behind upper
shock mounts, may be replaced with round, square, or rectangular tubing. No part of frame
can be lower than five inches from ground except front crossmember. No other frame
Must consist of continuous hoops, minimum 1.5 inch O.D. tubing, with a minimum wall
thickness of.095 inch for main cage. Cages must be steel or chrome-moly. Main cage no
further forward than rear of engine and no further back than front edge of rear tire. Four bars,
two per side, may extend from main roll cage to main frame points in front of the upper control
arms. These bars may have two additional braces per side to the main frame. Six bars may
extend from the main cage to the rear. X-bracing is allowed. Driver’s head must not protrude
outside cage with helmet on. Roll cage must be securely supported and braced with minimum
one cross bar in top halo. All bars forward of cage must be lower than hood.
Minimum of three driver side door bars required, minimum 1.5 inch O.D. and .083 inch wall
thickness, must be parallel to ground and perpendicular to driver, and welded to front and rear
of roll cage. Minimum two passenger side door bars required, must have at least one cross
door bar, horizontal or angled. Steel door plate, 18 gauge or .049-inch
CAR MUST BE IMCA LEGAL
(Same as IMCA Sport Modified) must be same width, front to rear, and parallel to OEM
frame. Engine compartment must remain open (no side panels). Aluminum or fiberglass hoods
allowed must completely cover top of radiator and engine, extending from nose to interior
deck and enclosed at rear. Must have front and rear roof supports. Aluminum or fiberglass
roof allowed, must meet body diagram. No Gremlin roofs. No plastic body panels or filler
panels allowed. Must have complete interior deck from side to side, must be aluminum or
sheet metal. Quarter panels must remain 90-degrees to ground, maximum 45-degree bend 4-
inches from bottom and 2-inches from top of doors and quarters. Rear spoiler may be
maximum 8 inches in material height and maximum 67 inches wide. Spoiler may have
stiffener, must be 1 inch or more down from top. Maximum 3 spoiler braces allowed, must be
mounted in line. Spoiler braces must resemble all aspects of drawing. No fins, lips or wings
Must have minimum three 5/16-inch O.D. windshield bars in front of driver. Aluminum cowl
panel in front of driver can be no wider than cockpit. Aluminum high-back seat only, must be
securely bolted, using minimum 0.375-inch bolts, to roll cage and support system. Floor pan
must be metal or aluminum and cover entire driver compartment. Bottom of seat can be no
lower than bottom of frame rail. Driver must be sealed off from track, driveline, engine, fuel
cell, canisters and pumps. No oil coolers allowed in driver compartment. No devices that
would enable driver adjustment to alter wheelbase or for weight jacking while car is in
competition. No mirrors of any kind.
All components must be steel, unaltered OEM, in OEM location, and match frame. No jack
bolts allowed. Adjustable spring buckets are allowed. Must use OEM upper and lower A-
frames and mounts. OEM upper A-frame may be replaced using aftermarket upper A-frame
(STEEL only). Upper A-frame mounts may be modified and moved for caster and camber
adjustment, but must remain OEM material. Lower A-frame mounts and bolt holes on frame
must be in OEM location, mount may be notched for clearance. All A-frame bushings may be
aftermarket, but no bearing/hemi type. OEM style ball joints only, may be tacked in. Sway
bars (optional) and brackets must remain OEM.
All components must be steel, unaltered OEM, in OEM location and match frame. No
grinding, lightening or welding on any steering parts. Spindle may be reamed and bolt on
spindle savers are allowed. Steel steering shafts and knuckles only. Steering quickener
(optional), steering wheel and quick release (required) may be aluminum. Power steering
pump and reservoir must remain one unit. Driver compartment steering may be modified,
must be kept on left side. No rack and pinion.
One steel shock per wheel only. Shock must be in OEM mounts and location, using OEM style
shock. Mounting spacers and weld or screw-on shock ends allowed. No air or coil-over shocks,
remote reservoir shocks, Schrader valves or bladder type valve allowed.
One steel spring (aftermarket allowed) per wheel only. Minimum 4.5-inches O.D.
All control arms and mounts must be steel, unaltered OEM, in OEM location, and match
frame. No jack bolts allowed. Adjustable spring buckets allowed, may be dropped as long as
they remain in OEM location. If upper spring cup uses all thread, it must be securely welded to
chassis. Lower spring cups must be centered on housing. Control arms may be reinforced, but
cannot be shortened or lengthened, must remain OEM length. All control arm bushings may be
aftermarket, but no bearing/hemi type. Bushings cannot be drilled. No aluminum parts
Must use OEM 7.5-inch GM 10 bolt rear end (bracing optional), must remain stock width. No
floater rear end allowed. Steel components only. OEM mounts on lower control arms must
remain in OEM location on original 7.5-inch tube housing. Aftermarket axles, mini-spools and
C-clip eliminators allowed. Locked rear ends only, no torque dividing differentials allowed.
No full or aluminum spools allowed. Pinion angle cannot be changed. Any gear ratio allowed
but housing must remain unaltered. No quick change devices.
Steel only. Two bar front bumper and single bar rear bumper must be used on car at all times
and welded, or bolted securely using minimum 0.375 inch bolts. Must be maximum 1.50-inch
O.D. tubing, .095-inch wall thickness on front and 1.75-inch tubing, .095 wall thickness on
rear. Maximum 1.50-inch O.D. tubing, .095-inch wall thickness fuel cell protection bar
required must cover rear and extend past both sides of cell may be welded to rear bumper.
Rear bumper may be maximum 6-inches beyond rear deck. All bumpers and kick rails must be
capped with no sharp edges. Single bar kick rail from front to rear wheel allowed on each side,
no center supports allowed, maximum 1.50-inch O.D. tubing and .095-inch wall thickness,
must be mounted to cage at front and rear of kick rail.
H 500 or IMCA 500 Race tire . 27 by 8 by 15 or 26.5 by 8 by 15 ‘stagger
tire’ allowed. Siping allowed. No grooving allowed. No re-caps. Steel bolts only. Outer
foam or plastic mud cover allowed on right rear only. Inner mud cover allowed on left rear
only. No bleeder valves. Must use minimum 1-inch O.D. lug nuts and 0.625-inch studs are
recommended. No wheel spacers allowed with OEM studs. Wheel adapters are treated as
spacers and may be aluminum.
Must be steel OEM, operative three wheels, drum or disc. Must maintain minimum OEM
dimensions for hubs/rotors and calipers cannot be lightened. Bolt pattern may be changed.
0.625-inch studs allowed.
Single or dual aftermarket master cylinders allowed. Driver
adjustable dual pedal brake bias allowed.
Additional proportioning valve (in-line type)
allowed, must be out of driver reach. Rear rotors may be aftermarket, minimum 0.810-inch
thickness, maximum 12-inch O.D. Vented rotors. Rear caliper brackets must be welded to
Must use Schoenfeld headers. GM: #161, #151, and #151E with 1.625-inch tubes and 3-inch
collector. Chrysler: #461, #461W2, and #462W2. Ford: #351, #361, #362, #562, #562-4B
#563-4B. No header modifications allowed. Coated headers allowed. No exhaust sensors
merge collectors, cross overs, turnouts or balance tubes. Mufflers optional.
Racing fuel cell required, maximum 22 gallon capacity and must be in a minimum 20 gauge
steel container. Must mount with minimum two solid steel straps around entire cell, two
inches wide and 0.125 inch thick, between frame rails in trunk area only. Fuel cell vents,
including cap vent, must have check valves. If fuel cell does not have aircraft style positive
seal filler neck/cap system – a flapper, spring or ball type filler rollover valve is required. No
part of cell can be lower than protective tubing. OEM mounted mechanical push rod fuel
pumps only. No regulators, bypass fuel systems, pressurized, or return lines allowed.
CARBURETOR (one only): Holley (unaltered) #4412 . Two-barrel may be used on Chevy. OEM
Motorcraft two barrel may be used on Ford. OEM Carter or AFB two barrel
may be used on Chrysler. OEM carburetors must remain unaltered; circle track floats may be
installed. No other carburetors allowed. Adapter/spacer allowed, maximum 1.250-inches
thick, including gaskets. No driver compartment adjustable carburetors or spacers.
Gasoline only. Racing fuel allowed. No performance enhancing product. Fuel must pass both
dielectric meter and chemical tests. Fuel sample may be taken from any car at any time.
Minimum weight limit of 2,300 pounds after race with driver in car. Weights must not be used
in driver compartment or outside body. All weights must be securely mounted with at least
two, .5-inch bolts, painted white with car number on it. Solid steel fasteners only.
One 12-volt battery only. Must be shielded and securely mounted. Aftermarket starter
allowed must bolt in OEM location. Must have capability of starting without being pushed or
No unapproved cameras, transmitting or listening devices, timing retard controls, or digital
gauges (including tach). No electronic monitoring computer devices capable of storing or
transmitting information except analog tach. OEM style ignitions only. GM: HEI distributor
(must remain one unit) or point distributor allowed. Ford/Chrysler: may use OEM ignition,
including OEM boxes, or HEI distributor. Any module may be used that fits inside the
distributor with no alteration. Vacuum advance may be removed and pick-up coil locked. No
external coils allowed, unless using point distributor. No GM or aftermarket ignition boxes
allowed. No traction control devices.
Only OEM production transmissions allowed. No aftermarket transmissions allowed. No ‘in
and out’ boxes or quick-change devices allowed. With engine running and car in a still
position, must be able to engage car in gear and move forward, then backward. Functioning
shift levers must be in OEM location. Transmission fluid coolers allowed. Flywheel, flex plate
and converter must be steel.
Automatic – A n y O E M a u t o m a t i c t r a n s m i s s i o n a l l o w e d . Must u s e
f u n c t i o n i n g , minimum 10-inch diameter steel torque converter. No direct drives,
couplers, valve pumps, or bleeder style valve bodies. Must have at least one forward
gear and reverse gear, gears must function. Must have an approved scatter shield
constructed of .125- inch by three-inch steel, 270 degrees around top of flexplate.
GM automatic must be used with GM engine, may be used with Ford or Chrysler
engine. Stall converters allowed. Steel OEM style flexplate only, must be bolted directly
to end of crankshaft. Manual – 3, 4 or 5 speed OEM manual transmissions only. All
gears must function. Must have functioning 10.5-inch minimum diameter steel
clutch and pressure plate bolted directly to steel flywheel. These components must
rotate, consistent with engine rpm, while car is in any gear. Must use explosion-proof
steel bell housing 180 degrees around top of clutch and flywheel. No mini-clutches or
couplers. Minimum 9-inch diameter Ford clutch allowed. Hydraulic slave
cylinder/throw out bearing allowed.
Drive Shaft – Minimum 2-inch diameter, white, steel drive shaft only. Steel slip-yokes
only. 360-degree drive shaft loop required, constructed of at least 0.125-inch by 2-inch
steel, or 1-inch tubing, mounted 6-inches back from front U-joint.
Rear of engine (bellhousing flange) must be mounted at least 70-inches forward from
centerline of rear axle. Minimum 11-inch engine height from ground to center of crankshaft.
One radiator allowed, steel or aluminum. Racing cap and electric fans allowed. Catch can
required. Power steering pump and reservoir must remain one unit and mount in front of
engine. Side engine mounts (OEM or 45-degree style) must be steel, aluminum mid-plate
Must use OEM cast iron, American make V-8 small block engines only. No bowtie, SVO or
W-2 components allowed. All engines must be able to be used in conventional passenger car
without a l t e r a t i o n s . External e n g i n e c a s t i n g a n d t h r e a d e d h o l e s c a n n o t b e
a l t e r e d . No aluminum, titanium or carbon fiber components allowed. GM crate engine and
Holley 4 barrel
GM (Chevy only): 283, 302, 305, 307, 327, 350. Ford: 260, 289, 302, 351. Chrysler: 273, 318,
340, 360, no hemi. Maximum cubic inch limits: GM 364 c.i., Ford 360 c.i., Chrysler 370 c.i.,
no tolerance. No 400 or larger cubic inch parts allowed. Flat top or dished cast pistons only;
Chevy must use 4-valve relief. No gas ported or floating pistons. 3.48-inch maximum GM
stroke. Maximum 175 lbs. per cylinder compression, no tolerance. Compression checked with
one spark plug removed, turned five engine revolutions. Engines may be balanced and block
decked. Oil filter system must remain OEM. ‘Wet’ sump-oiling system only. No accusumps.
OEM rods. Chevy must use maximum 5.7-inch rod. Steel or cast OEM crankshafts only. No
splayed main caps. Racing oil pans allowed. One-inch inspection hole recommended in pan –
no obstructions to crank and rods. If obstructions are present, must remove pan for inspection.
Engine bolts may be aftermarket. Fluid dampener balancer allowed. No roller bearings
INTAKE – Unaltered, approved OEM cast iron low rise, two- or four-barrel; or
unaltered Weiand aluminum Chevrolet #7547-1, Edelbrock #EDL-2701, Ford 302
#7515, 351 Windsor #8023, 351 Cleveland #7516, Chrysler #7545. No porting,
Polishing, or alterations of any kind, including cooling lines or plenum alterations to
ANY intake. No OEM hi-rise, marine or bowtie intakes. Ford may use OEM aluminum
intake, no under air or hi-rise. All intakes must have unobstructed 0.250-inch vacuum
fitting. Belt driven, OEM style water pumps only, no aluminum water pumps on Chevy
CAMSHAFT – Non-roller hydraulic cam/lifters only. Hydraulic lifters must remain
UNALTERED OEM. No maximum cam lift. Must pull 12-inches of vacuum at 1200
rpms. Vacuum to be pulled at intake vacuum fitting, not carburetor. No alterations of
any kind may be made at time of tech. Track equipment being used for tech is final.
Lifter bores cannot be altered. Must be chain driven no gear/belt drives.
CYLINDER HEADS – Only GM OEM approved head numbers are (last 3 digits): 126,
185, 336, 441, 445, 487, 493, 598, 624, 862, 882, 920, 993, 997, with valve no larger
than 1.94-inch intake and 1.50-inch exhaust. May use Engine Quest (EQ) Stock
Replacement (SR) cylinder head, part number CH350I, head must remain as produced,
valve sizes cann ot be changed. No porting, polishing, or unapproved alterations to
ANY cylinder head. Any cast iron OEM Ford and Chrysler heads allowed with valves
no larger than 2.04-inch intake and 1.70-inch exhaust. Headers must bolt directly to
heads with correct numbers. No vortex, bowtie, SVO, W-2 or aftermarket heads
allowed. Flat milling allowed. Guide plates, screw-in shouldered studs (0.375-inch
max) and polylocks allowed, no stud girdles. Stamped steel, OEM style, stud mounted
(0.375-inch max) rocker arms only. Chrysler may use OEM rocker arm bars. Any
length push rods allowed. OEM diameter springs must match heads (no beehive valve
Protest money must be in the hands of the promoter BEFORE the “A” Main starts.
Tear-down fee of $300 will require the removal of one (1) cylinder head and related
components to allow measurement of bore and stroke and to see piston dome type.
$50 of the protest fee goes to the track; no matter the results of the protest.
Person protesting must take the green flag in the “A:” Main that night and be signed in to the
pits that night. Only registered car owner in the Limited Modified registration for the current year at this track
Owners may protest one (1) time in a four week time span on the same car.
First refusal to remove head for testing results in the loss of all points and pay for that night.
Second refusal results in that night’s pay and all points for the whole season being lost.
Track may tear-down or inspect any car, any time, for any rule violation without money or
protest fees posted.
If the protest is considered ILLEGAL on any components listed above than the driver is
disqualified for the night and does not receive points or pay for that night. If the protest is
considered LEGAL then the owner making the protest loses his fees and the owner of the car
that was tore-down receives the $250 protest fee.
· There is no longer an engine claim. INFRACTION OF ANY RULES STATED ABOVE WILL
RESULT IN LOSS OF POINTS, MONEY, and AWARDS FOR THE NIGHT. DON’T COME
BACK UNTIL YOUR CAR IS LEGAL. Clarifications of these rules can be made at the race
track at anytime!
IF IT DOESN’T SAY YOU CAN DO IT………YOU CANNOT DO IT!
Superbowl Speedway reserves the right to make modifications as necessary
throughout the racing season.