1. SAFETY EQUIPMENT:
Rules apply at all times car is on track. Snell-rated SA2010 or SA2015 helmet required. Roll bar padding required in driver compartment. Recommended: Fire retardant padding. SFI-approved full fire suit required. Fire retardant gloves, shoes and neck brace (or head and neck restraint) required. Right and left seat head supports required
if using head and neck restraint system. Recommended: Fire retardant head sock and underwear, collapsible steering shaft. Driver-side window net required, minimum 16 inch by 20
inch ribbon or mesh style, and must be mounted to roll cage so latch is at top front of window. Maximum four inch tall visor attached to window net. Minimum three inch (two inch with
head restraint system) wide SFI-approved five point safety belt assembly required, must be mounted securely to main roll cage. Recommended: Safety belts no more than two years old.
Kill switch required within easy reach of driver and must be clearly marked ‘OFF’ and ‘ON’.
(see frame drawing) 1978-1987 OEM midsize GM metric full frame only. Minimum wheelbase 107 inches, maximum 109 inches, both sides, maximum one inch difference
from side to side. 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 or body can be lower than five inches from ground except front crossmember. No underslung or other frame
alterations allowed. See www.imca.com for OEM frame dimensions.
3. ROLL CAGE:
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.
4. DOOR BARS:
Minimum 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, and one horizontal top door bar. Steel door
plate, 18 gauge or .049 inch, required.
(See diagram) No composite or plastic body panels allowed except roof rock guard and hood scoop. Body and interior deck must be same width, front to rear, and parallel to
OEM frame. Aluminum nose panel must be flat. Maximum 2.250 inch side fins allowed on aluminum nose. IMCA-approved plastic nosepieces allowed. Nose must be mounted in an
approved manner and can extend no higher than front top of hood. Nose piece must remain inside confines of front bumper (exception is plastic valance) and be no lower than four inches
below frame horns. Cooling holes allowed. Engine compartment must remain open (no side panels). Hood must cover radiator, be level or sloped down at front, enclosed and maximum
two inches above interior deck at rear. No reverse hood rake allowed. No panel in front of right door to engine compartment. No inner panels. No complete or half-car covers, rear tail
cover allowed in personal pit area only. Must have front and rear roof support posts. Driver and passenger side windows must have at least 12 inch opening (height and width). Full size,
fiberglass or aluminum roof only (see diagram). No dished roofs allowed. Driver roof hatch allowed. Maximum 1.5 inch rolled down rock guard allowed on roof front. Maximum four
inch roof sides allowed. Maximum one inch ridge down sides of roof. Maximum one inch rear roof stiffener (must face down). Solid sail panels must resemble all aspects of drawing and
may not extend ahead of back of seat. Rear spoiler (optional) may be minimum one inch or maximum eight inches in material height and maximum 67 inches wide. Spoiler may have
rear stiffener, must be one inch or more down from top. Maximum three spoiler braces allowed, must be mounted in line. Spoiler braces must resemble all aspects of drawing. Spoiler
must be mounted within confines of spoiler braces. No fins, lips, wings or vortex generators allowed. Maximum four inch plastic skirting allowed on bottom of doors and quarters. Car
number must be minimum four inches thick and 20 inches tall and clearly visible, on both sides and roof of car; six inches tall on front and rear.
6. DRIVER COMPARTMENT:
Must have minimum three windshield bars in front of driver. Lexan or aluminum cowl panel in front of driver can be no wider than cockpit and no further
back than steering wheel. Floor pan must be metal or aluminum and cover entire driver compartment. Aluminum high-back seat only, must be securely bolted, using minimum 0.375 inch
bolts, to roll cage and support system. Bottom of seat can be no lower than bottom of frame rail. Driver must be sealed off from track, driveline, engine, fuel cell, cannisters 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.
7. FRONT SUSPENSION:
All components and mounts must be steel, unaltered OEM, in OEM location, and match frame. All A-frame bushings may be aftermarket, but no offset or
bearing type. No sway bars or jack bolts allowed. Exceptions are: adjustable spring buckets are allowed. OEM upper A-frame mount may be moved or replaced (OEM material no longer
required) with aftermarket steel non-adjustable mount matching upper A-frame bolt on design. OEM upper A-frame may be replaced using aftermarket upper A-frame, must display
“IMCA approved” decal. Upper solid steel shock mount may be maximum four inches above frame. Lower A-frame mount may be notched for clearance. OEM or OEM replacement
ball joints allowed, may be tacked in. No suspension stops of any kind allowed.
All components must be steel, unaltered OEM, in OEM location and match frame. Exceptions are: tie rod adjusting sleeve may be replaced with 5” steel tube, replacement
spindle with Speedway Motors raised cast – part number 91034501; bolt on OEM spindle savers 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 unaltered steel, nonadjustable, OEM mount shock, in OEM location, per wheel. All shocks must completely collapse at any time. No external or internal bumpers or
stops. Mounting spacers and weld or screw-on shock ends allowed. No coil-over shocks, air shocks, remote reservoir shocks, or shock covers. No Schrader or bladder type valve allowed.
One or all shocks may be claimed per event for $50 each, counting as one claim on card, following shock claim procedures (Refer to www.imca.com).
10. SPRINGS: One steel closed end spring (racing allowed) per wheel only. Minimum 5.5 inches (front), minimum 4.5 inches (rear) O.D., non-progressive coils only. No torsion bars or air bags.
11. REAR SUSPENSION:
All components and mounts must be steel, unaltered OEM or OEM replacement, 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 offset or bearing
type. Bushings cannot be drilled. No suspension parts may be altered or lightened. No aluminum parts allowed, other than bushings. No suspension stops of any kind allowed.
12. REAR END:
Must use OEM 7.5 inch GM 10 bolt rear end (bracing optional), must remain stock width. No Ford or floater rear end allowed. Housing end, from control arm mount out, may be
modified with three inch tubing to accept nine inch Ford axle. If Ford axles are used, rearend must remain minimum GM width or maximum three inches wider. 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.
13. BUMPERS/RUB RAILS:
(see diagram) Steel bumpers must be on front and rear and welded, or mounted with minimum 0.375 inch bolts. Two bar front bumper must be minimum 1.25
inch O.D. tubing with minimum .065 inch wall thickness (maximum 0.095 inch) mounted frame end to frame end, no wider than width of material outside frame horns and with bottom
loop parallel to ground. Top bar must be directly above bottom bar, minimum 6.5 inches apart, measured center to center. Rear bumper must be constructed of solid square, or minimum
1.25 inch O.D. tubing with 0.095 wall thickness, (similar to diagram), maximum six inches beyond rear deck, no wider than five inches outside of rear frame rails. If wider than five inches
outside rear frame rails, must be bent forward 90 degrees, or constructed in a loop design. Must have at least one upright, minimum 1.25 inch with 0.065 wall thickness, from bumper to fuel
cell guard. All bumpers and rub rails must be capped with no sharp edges. Single bar rub 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 rub rail.
Must use unaltered Hoosier ‘500’ Race tire, with IMCA stamped on sidewall. 27 x 8 x 15 or 26.5 x 8 x 15 ‘stagger tire’ allowed. No chemical softening, conditioning
or grooving of tires (Refer to www.imca.com for automatic penalties). Tires may be ground or straight siped within confines of tread. All wheels must be unaltered and display white “IMCA
approved” decal and wheel manufacturer decal. Any offset allowed. May use IMCA approved bead lock, on right rear only. External steel bead lock only and it cannot make wheel any narrower
than eight inches and no wider than 8.75-inches. Steel bolts only. Foam type or securely bolted plastic outer mud cover allowed on right side wheels. Outer mud cover mounting tabs and rings
must be integral to the wheel or bead lock or be securely welded to wheel. Aluminum inner mud cover allowed on left rear only. No bleeder valves. Must use minimum one inch O.D. steel lug
nuts and 0.625 inch studs are recommended. Aluminum wheel spacers only. Wheel adapters are treated as spacers, maximum 1.50 inches thick.
Must be steel OEM, operative four wheel, drum or disc. Right front brake shut-off allowed. Must maintain minimum OEM dimensions for hubs/rotors and calipers, cannot
be lightened. No oil bath front hubs. Bolt pattern may be changed. Larger 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 0.81 inch thickness (new), maximum 12 inch O.D.
Vented solid surface rotors only, no scalloped or ceramic coated rotors. Rear caliper brackets must be welded to housing.
Must use one of following header part numbers: Schoenfeld – GM #161, #151, #151E, or GM #161CM, #151CM, #151ECM (for crate motor) with 1.625 inch tubes and
three inch collector. Chrysler: #451, #461. Ford: #351, #361, #562, #562-4B. Dynatech – GM #701-16210, #701-10010. Collector and turn down length maximum nineteen inches total.
No header modifications allowed. No pan evac systems, exhaust sensors, merge collectors, cross-overs, inserts, cones or balance tubes. Coated headers allowed. Schoenfeld mufflers,
stamped IMCA609, IMCA930 or IMCA935, must be used if track has noise reduction rule of 98 dB or more.
Headers must be 1 5/8 primary 3″ collector headers must remain independent no merging of any kind.
17. FUEL SYSTEM:
Racing fuel cell required, maximum 22 gallon capacity (Recommended: 12 gallon), must be in minimum 20 gauge steel container. Must mount with minimum one
inch square tubing or two solid steel straps around entire cell, two inches wide and 0.125 inch thick, between frame rails and behind rear axle. 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. Fuel shut-off recommended.
No part of cell can be lower than protective tubing. No regulators, bypass fuel systems, pressurized, or return lines allowed. One fuel filter allowed. No cool cans. Any air cleaner
allowed. No cold air boxes or ducting of any kind between engine and hood. Mechanical OEM type push rod fuel pumps only. Maximum 0.100 inch thick carburetor gaskets on all
engines. CLAIM ENGINE: must use IMCA approved naturally aspirated, unaltered 500 c.f.m. Holley – part no. 0-4412, may be modified to Holley HP Dorton part no. 0-80583-1
specs only. Float bowl must face forward. Any adapter, maximum one inch thick. No throttle bore adjustable carburetor spacers. GM CRATE ENGINE: may use any Holley four-barrel
carburetor, all components (float bowls and main body) must be Holley manufactured. Metering blocks and base plate may be billet aluminum non-Holley. No aerosol-style carburetors
allowed. May use Speedway Motors part #545-64940 or Moroso part #64940 carburetor spacer on crate.
Gasoline only. Racing fuel allowed. No E85. No performance enhancing additives or scented additives. Fuel must pass both dielectric meter and chemical tests. Fuel sample
may be taken from any car at any time (Refer to www.imca.com for automatic penalties).
19. WEIGHT: Minimum weight limit of 2,350 pounds after race with driver in car. Ballast must not be used in driver compartment or outside body. All ballast must be securely mounted
with at least two 0.5 inch bolts, painted white with car number on it. No titanium, magnesium, stainless steel, carbon fiber or tungsten components. Solid steel fasteners only.
1800 West D Street
P.O. Box 921
Vinton IA 52349-0921
319-472-2201 24-hour fax 319-472-2218
One 12 volt battery only, must be securely mounted between frame rails and positive terminal must be covered. Aftermarket starter allowed, must bolt in OEM location
and directly engage flexplate/flywheel. Car must have capability of starting without being pushed or pulled. Car must leave initial staging area on demand, unaided, or go to rear of that race.
No unapproved cameras, transmitting or listening devices (exception is one-way Race Receiver radio by officials), timing retard controls, or digital
gauges (including tach). No electronic monitoring computer devices capable of storing or transmitting information except memory recall analog tach. 12 volt ignition system and OEM
HEI style ignitions only. Ford/Chrysler must use HEI distributor. No crank triggers. Any module that fits inside distributor with no alteration allowed. Crate engine MUST use unaltered
MSD #8728 or #8727CT rev-control and 6,200 rpm chip. Claim engine MAY use MSD #8728 or #8727CT rev-control with any rpm chip. (Refer to www.imca.com for automatic
penalties.) No unapproved or additional ignition accessories allowed. All components must be out of reach of driver, but with rev-control easily accessible facing up or out for inspection.
All wiring must be visible for inspection. Only gauges allowed are analog oil pressure, fuel pressure, brake bias, water temperature and tach. OEM type alternator with internal regulator
allowed. No electronic traction control devices. (Refer to www.imca.com for automatic penalties).
22. TRANSMISSION/DRIVE SHAFT:
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, flexplate and converter must be steel.
Automatic: Any OEM automatic transmission allowed. Must use functioning, minimum 10 inch diameter steel torque converter. No direct drives, couplers, valved pumps, or bleeder
style valve bodies. Must have at least one forward gear and reverse gear, gears must function. Must have an approved scattershield constructed of .125 inch by three-inch steel, 270
degrees around top of flexplate. Aluminum OEM bellhousing may be replaced with aftermarket explosion-proof steel or aluminum bellhousing. 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. No bump starts allowed.
Manual: Three, four or five speed OEM manual transmissions only. All gears must function. Must have functioning 10.5 inch minimum diameter clutch and OEM appearing 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 bellhousing 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: Steel slip-yokes only. Minimum two inch diameter, white, steel drive shaft only. 360-degree drive shaft loop required, constructed of at least 0.125 inch by two inch steel,
or one inch tubing, mounted six inches back from front U-joint.
23. ENGINE COMPARTMENT: 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, 27 inches by 19 inches maximum in size, must be mounted in front of engine. Racing cap and electric fans allowed. No
sprinklers. Power steering pump and reservoir must remain one unit and mount in front of engine. Side engine mounts only (OEM or 45-degree style) must be steel, aluminum mid-plate
allowed. No vacuum pumps, oil coolers or remote oil filters. Belt driven, OEM style water pumps only, no aluminum water pumps on GM engine.
24. ENGINE OPTIONS AND SPECIFICATIONS:
All cars utilizing the GM602 crate engine must clearly display on both front roof posts the Chevrolet Performance emblem.
(A) CRATE ENGINE: Must use unaltered sealed GM #88958602 or #19258602 crate engine. Effective January 1, 2019, all GM 602 Crate engines must have IMCA Cable-Lok seals. Upon
inspection, any different, altered or missing GM seal bolts will result in IMCA penalty (see www.imca.com, Automatic Penalties for crate engine rule violations). GM seal bolt exception
is IMCA approved and issued Cable-Lok repair system, and oil pan may be replaced by IMCA certified repair center with IMCA approved Champ pan #CP57LTRB and Champ pick-up
#1012SB. Any driver using crate engine cannot claim engine or have engine claimed. During same season, no driver is allowed to claim an engine after competing with a crate. If a driver
switches to a crate after claiming an engine, the crate engine is then claimable.
(B) CLAIM ENGINE: All engines must be able to be used in conventional passenger car without alterations. External engine casting and threaded holes cannot be altered.
BLOCK: OEM steel passenger vehicle production block only. No GM bowtie, Ford SVO or Chrysler W-2 components allowed. GM approved blocks are: 10105123, 10066034, 283, 302, 305, 307,
327, 350. Ford: 260, 289, 302, 351. Chrysler: 273, 318, 340, 360, no hemis. Maximum cubic inch limits: GM 364, Ford 363, Chrysler 370, no tolerance. Violation of cubic inch limit must be verified
by removal of head and will result in disqualification, loss of all IMCA points for the season, $1,000 fine and a 30-day suspension. No 400 or larger cubic inch parts allowed. Any flat top or dished
pistons allowed, no gas ported pistons. Stroke must match block. Maximum 175 lbs. per cylinder compression, no tolerance. Compression checked with one spark plug removed, turned five engine
compression revolutions (with throttle closed). Engines may be balanced and block decked. Oil filter system must remain OEM. ‘Wet’ sump oiling system only. No accumulators or external oil lines.
OEM or OEM appearing replacement steel crankshaft only – cannot be lightened. No aerowing, bullnose, knife edge, undercut or drilling of second or third rod throws allowed. OEM or OEM cast
appearing replacement steel rods only – GM must use maximum 5.7-inch rod or GM Vortec rod part number 10108688. Cap screw rods allowed. No splayed main caps. Racing oil pans allowed.
Mandatory one inch inspection hole in all pans – no obstructions to crank and rods. Engine bolts may be aftermarket. Fluid dampener balancer allowed. No roller bearings allowed.
CYLINDER HEADS: Steel only. GM OEM approved head numbers are (last 3 digits): 126, 185, 336, 441, 445, 487, 487X, 493, 598, 624, 862, 882, 920, 993, 997, with valve no larger than 1.94 inch
intake and 1.50 inch exhaust. May use Stock Replacement (SR) cylinder heads: Engine Quest (EQ) GM part number CH350I, (EQ) Chrysler part number CH318B, World Products Ford part number
53030 – 1.250 inch (± .015 tolerance) maximum O.D. valve springs. All SR heads must remain as produced, seat angles and valve sizes can not be changed: three angle valve job only (absolutely no
casting removal in valve pocket of EQ or World Products head, for any reason). No porting, polishing, or unapproved alterations allowed to ANY cylinder head or intake, disqualification and $250
fine if illegal. 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
vortec, bowtie, SVO, or W-2 heads allowed. Flat milling allowed. Guide plates, screw-in shouldered studs (0.375 inch max) and polylocks allowed. No stud girdles. Steel roller tip rocker arms allowed.
Chrysler may use OEM rocker arm bars. Any length push rods allowed. OEM diameter springs (GM – 1.250 inch maximum O.D.) must match heads, no beehive valve springs allowed.
INTAKE: Unaltered, approved OEM cast iron low rise, two- or four-barrel. Only unaltered (no porting or polishing) aftermarket aluminum intakes allowed are: Weiand GM #7547,
#7547-1; Ford #7515, #8023 or #7516; Chrysler #8022; Edelbrock GM #2701; Ford #7121, #7181, #7183; Chrysler #2176. Cooling lines allowed on aluminum intakes. Ford may use
OEM aluminum intake, no under air or hi-rise.
CAMSHAFT: Conventional flat tappet cam and lifters allowed, cannot alter lifter bores. OEM firing order cannot be changed (GM: 1-8-4-3-6-5-7-2). No maximum cam lift. No vacuum
rule. Must be chain driven, no gear/belt drives.
25. ENGINE CLAIMING RULES:
Refer to www.imca.com for claim eligibility requirements.
(A) $550 cash and exchange claim on engine ($25 goes to wrecker and $25 to official for each engine)
(B) Claim does not include – 1. flywheel, 2. clutch, 3. pressure plate, 4. bellhousing, 5. breathers, 6. carburetor, 7. starter, 8. motor mounts, 9. oil/temp. sending units, 10. fan and pulleys, 11.
clutch ball, 12. clutch arm, 13. throw out bearing, 14. dip stick, 15. water pump, 16. fuel pump, rod and plate, 17. distributor, 18. plug wires, 19. water outlet and restrictor, 20. headers.
NOTE: During engine claim, block and head numbers should be verified, head, intake, connecting rods and crankshaft should be visually inspected and one spark plug must be removed
to check pistons prior to transfer of engines. If, at this time, an engine is found illegal, driver is disqualified and suspended from all IMCA sanctioned events until such time as a $250
fine is paid, for first offense. Exchange of engines may proceed depending on circumstance. Decision to proceed is at discretion of track officials and/or IMCA.
The above rules have been imported from the official IMCA website, Rules are subject to change without notice.
Please check the IMCA website for any changes and updates.