HOBBY STOCK - 2019
1800 West D Street
P.O. Box 921
Vinton IA 52349-0921
Revised October 2018. phone: 319-472-2201
Refer to www.imca.com for General Rules.
rules and/or regulations set forth herein are designed to provide for the
orderly conduct of racing events and to establish minimum acceptable
requirements for such events. These rules shall govern the condition of all
events, and by participating in these events, all participants are deemed to
have complied with these rules. NO EXPRESSED OR IMPLIED WARRANTY OF SAFETY SHALL
RESULT FROM PUBLICATIONS OF OR COMPLIANCE WITH THESE RULES AND/OR REGULATIONS.
They 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.
race director shall be empowered to permit reasonable and appropriate deviation
from any of the specifications herein or impose any further restrictions that in
his opinion do not alter the minimum acceptable requirements. NO EXPRESSED OR
IMPLIED WARRANTY OF SAFETY SHALL RESULT FROM SUCH ALTERATION OF SPECIFICATIONS.
Any interpretation or deviation of these rules is left to the discretion of the
officials. Their decision is final.
one with an IMCA license during the same calendar year in any other division may
compete in this division, except: licensed Sport Compact or SportMod™ drivers
(must still purchase Hobby Stock license). Unless otherwise noted, all parts to
be approved OEM and must match make and year of car.
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’.
FRAME: (see frame
drawing) Any American OEM full body rear wheel drive passenger car, 1964 or
newer, full frame or unibody. Frame must match body. Minimum 107.5 inch
wheelbase, maximum one inch difference from side to side. Rear of frame behind
rear tires, no further forward than one inch behind factory seam, may be
replaced in OEM location with two inch by three inch steel tubing with minimum
0.083 inch wall thickness, same length as material removed. Factory seam must
remain visible. Unibodies must tie rear frame to front frame. Frames may be
“X” braced. No Station Wagons, Camaros, Firebirds, or Mustangs.
ROLL CAGE: Main
cage must consist of continuous hoops, minimum 1.75 inch O.D. tubing, with wall
thickness of at least 0.095 inch. Recommended:
low carbon or mild steel. Four-post roll cage required, front down bars and
rear hoop must be welded to OEM frame. Driver’s head must not protrude outside
cage with helmet on. Rear hoop must have “X” brace, consisting of one full
horizontal and one full diagonal bar, minimum 1.25 inch O.D. with 0.083 inch
wall thickness. Front down bars must be tied together, passenger side front down
bars must be maximum 11 inches in from top of door. Must be minimum 40 inches
between outside edge of front and rear down bars at top of door panel. Maximum
41 inches from top center of windshield to front edge of rear hoop; maximum 13
inches to front edge of top halo. Top halo must be minimum 40 inches across,
outside to outside. Rear hoop may be maximum 12 inches in from bottom of opera
window. Minimum one cross bar in top halo. May have maximum two horizontal bars,
(in addition to bar tying front frame horns together) for radiator protection;
must be behind bumper, within confines of body, no wider than OEM frame horns.
Rear kickers (down bars) and engine hoop required, and must be minimum 1.25 inch
O.D. tubing with 0.083 inch wall thickness. Fuel cell protection required, must
be mounted frame rail to frame rail, no higher than fuel cell, inside trunk area
with maximum 1.75 inch O.D. tubing. All bars must be inside body.
DOOR BARS: All door
bars and uprights must be minimum 1.75 inch O.D. with 0.095 inch wall thickness.
Minimum three door bars, both sides, parallel to ground, and perpendicular to
driver. Minimum four uprights tied from frame to top door bar on driver side,
and minimum three uprights on passenger side. Steel door plates, 18 gauge or
0.049 inch minimum thickness, must be securely welded to outside of door bars on
driver’s side. Plate must cover area from top door bar to rocker panel and
from rear down post to five inches in front of seat. Must be visible for
BODY: All bodies
must be approved unaltered OEM, or OEM replacement, in OEM location and match
frame. Maximum 31 inches from back of engine
block to front edge of GM metric roof. Front body mounts must be visible.
Sunroofs and T-tops must be enclosed. OEM appearing aftermarket plastic
nosepiece allowed (must match body on GM metric car), minimum
9 inch ground clearance. OEM appearing
aftermarket plastic tailpiece allowed (recommended to match body). Tailpiece must be trimmed for unaltered
trunk lid. No metal fabricated rear tailpieces allowed. No spoilers, hood
scoops, ground effects or skirting altering OEM appearance allowed. OEM STEEL
hood only, maximum three inch bow, hood may be gutted. OEM STEEL unaltered trunk
lid only, no gutting. Hood and trunk must be securely fastened and back of hood
must be sealed off from driver compartment with metal. Hood must be separate
from fenders. Front and rear inner wheel wells may be removed. Trunk floor
directly over rear end housing must be removed. Trunk floor may be replaced,
frame rail to frame rail, with 0.049 inch thick steel, must be located on top of
frame rail. Overlapping of body panels permitted. All glass must be removed, all
windows in body must remain open; maximum seven inch metal sun visor allowed
across top of windshield opening. All doors must be securely fastened. Fenders
and quarter panels may be trimmed for tire clearance, ONLY. 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. No Station Wagons, Camaros,
Firebirds, or Mustangs.
Minimum three windshield bars in front of driver. Aluminum high-back seat only
and must be bolted in using minimum 0.375 inch bolts. Driver seat may be no
further back than rear edge of B-pillar. Driver must be sealed off from track,
driveline, engine and fuel cell. Dash not to extend more than 24 inches back
from center of lower windshield opening. Dash must be flat, rear can be no
higher than front, except for cowl in front of driver. No other interior tin or
covers. Inside rear quarter panels, below window level, may be cut out. Doors
and driver side B-pillar may be gutted. No cutting out roof except for roll cage
clearance. Kick and rocker panels may be
removed. Front OEM firewall may be replaced using steel fabricated
full firewall, 18 gauge or minimum 0.049 inch thickness. Front firewall may be
no further back than the rear of oval frame hole, must be vertical and 24-26
inches tall. All holes in firewalls and floor must be covered. OEM floor may
be replaced from OEM front firewall to OEM rear firewall using steel fabricated
floor pan, 18 gauge or minimum 0.049 inch thickness, securely welded to frame.
Must remain flat, OEM appearing from frame rail to frame rail, no higher or
lower than frame rail. Exception is maximum eight inch tall driveshaft tunnel
similar to OEM tunnel in size. Rear firewall and speaker deck must be metal and
be of OEM design for that make and model. Firewalls
must extend to body. No mirrors of any kind.
All components and mounts must be steel, unaltered OEM, in OEM location and
match frame. OEM rubber A-frame bushings only. OEM or OEM replacement ball
joints allowed. No rebuildable ball joints. No sway bars, spring spacers, chains
or cables. Exceptions are: for 1978-1987 GM mid-sized metric frame, OEM upper
A-frame may be replaced using aftermarket upper A-frame (steel or aluminum cross
shaft allowed), must display “IMCA approved” decal on top of rear tube of
A-frame. Upper A-frame mount must remain OEM and cannot be moved. No suspension
stops of any kind allowed.
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
(metric frame only); bolt on spindle savers allowed; OEM steering column may be
replaced with steel knuckles and steel steering shafts (collapsible
recommended), steering wheel and quick release (required) may be aluminum.
No steering quickeners (minimum 2.5 turns lock to lock), or remote power
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. No bulb-type, threaded body, coil-over, air, or remote reservoir shocks.
Maximum 2.125 inch O.D. shock body. No gas port, Schrader or bladder type valve
allowed. No coil-over eliminators. Rear OEM shock location is 4.5 inches from
bottom of housing to center of bolt hole, and centered on control arm bracket.
$25 claim on any shock. One or all shocks on car may be claimed per event,
counting as one claim on card, following shock claim procedures and penalties
(Refer to www.imca.com).
SPRINGS: One steel
closed end spring per wheel only in OEM location. Minimum 4.5 inches O.D.,
maximum 14 inch free height, non-progressive coil springs only. No spring
All components and mounts must be steel, unaltered OEM or OEM replacement, in
OEM location and match frame. OEM rubber control arm bushings only. Center of
rear lower control arm bolt hole must be 2.25 to 2.5 inches from bottom of
housing. No independent rear suspension. No sway bars, panhard bars, spring
spacers, extensions, chains or cables. No suspension stops of any kind allowed.
REAR END: Approved
OEM housing and carrier only. No floater rear ends. OEM, or OEM replacement
(recommended) solid steel axles only. Nine inch Ford rear end allowed, but must
be mounted like OEM rear end (centered) for that make and model. One inch
inspection hole in housing required. Ring gear, center section and yoke cannot
be lightened. Steel or aluminum U-joint caps allowed. Welded spider gears or
mini spool only. No scalloped ring gears, cambered rear ends, heavyweight axle
tubes (max .250” wall) or housing braces.
Maximum one inch wide by two inch tall steel or lexan rub rails allowed - bolted
flush to body. Front and rear tow hooks mandatory. No sharp edges allowed on
bumpers, rub rails or bolts. No bars past outside edge of body other than rub
rails. All front bumpers must be mounted minimum six inches from front frame
horns. Steel bumper mounts only. One of two bumper options must be used and must
be OEM height: OEM: Bumpers not covered by plastic nose or tail piece must be
complete, unaltered OEM, capped to fender with steel, welded or bolted.
Aftermarket: Fabricated tubular bumpers (front and rear) allowed, but must be
covered by plastic nose or tail piece and bent to fit with rounded ends. Main
bumper bar must be minimum 1.5 inch O.D. (maximum two inch) with 0.083 inch
(maximum 0.125 inch) wall thickness.
Unaltered OEM 205/75, or 205/70, 14 inch or 15 inch passenger car tires only.
All four tires and wheels must be same size. Tires must be inside body. No
racing, snow, or all-terrain tires. No softening, conditioning, siping/grinding
or grooving (Refer www.imca.com for automatic penalties). Maximum seven inch
wide, three to four inch offset, unaltered, D.O.T.-stamped steel wheels with
standard bead bump - must weigh minimum 21 pounds. No wheel spacers or bleeder
valves. One inch O.D. steel lug nuts required.
unaltered OEM, or unaltered OEM replacement, operative four wheel, disc (front)
and drum (rear) brakes, must match frame or rear end. Full OEM backing plates,
no aftermarket. OEM or OEM appearing master cylinder must be in OEM location. No
antilock brake systems. No aftermarket brake pedal assemblies, brake shut-off or
bias adjuster. Steel brake lines only, must be visible. No oil bath front hubs.
Hubs/rotors, axle flanges and drums may be changed to different bolt pattern and
EXHAUST: OEM cast
iron exhaust manifolds only. No center dump type manifolds. Exhaust manifold can
be ported and drilled to fit. No adaptor allowed between manifold and head. All
engines must use maximum two inch O.D. exhaust pipes. Exhaust must extend past
firewall and turn toward ground. Must remain dual exhaust, no crossover or
‘Y’ pipes. No pan evac systems, exhaust sensors, coatings or wrap. Mufflers recommended.
FUEL SYSTEM: Racing
fuel cell required, maximum 22 gallon capacity (Recommended:12
gallon), must be in minimum 20 gauge steel container. Must be securely
fastened in trunk above level of OEM trunk floor, behind rear tires, no further
forward than factory seam where rear frame rail can be replaced, with minimum
one inch square tubing or two solid steel straps around entire cell, two inches
wide and .125 inch thick. No fuel cells allowed over rear end housing. Metal
firewall must be between driver and fuel cell. All cell mounts must be steel,
securely welded to frame/cage. No adjustable fuel cell mounts. 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 lines through driver compartment must
run through metal pipe or metal conduit. One fuel filter allowed, cannot be in
driver’s compartment. No cool cans. Air cleaner top/stud cannot direct air
into carburetor. No top flow air cleaner housings, cold air boxes or air cleaner
ductwork. Mechanical OEM type push rod fuel pumps only. No fuel pressure
regulators. Fuel shut-off recommended.
CLAIM ENGINE: must use unaltered OEM
two barrel carburetor for that engine, except: booster I.D. may be machined to
0.25 inch, venturi I.D. machined to 1.375 inch and throttle bore I.D machined to
1.6875 inch on Rochester carburetor. 0.625 inch minimum booster height on
Rochester carburetor. Must remove carburetor choke plate. No carburetor spacers
on cast iron intake. One 0.25 inch (maximum) thickness gasket only on cast iron
intake. Speedway Motors carburetor adaptor, part #135-3502G, allowed on aluminum
intake with Rochester carburetor. Speedway Motors carburetor adaptor, part
#135-3502G, allowed on GM aluminum intake. Mr. Gasket carburetor adaptor, part
#1933 with OEM carburetor, or Speedway Motors carburetor adaptor part #135-3502G
with Rochester carburetor allowed on Ford and Chrysler aluminum intake. Maximum
of two 0.100 inch thick carburetor gaskets on all aluminum intakes. GM
CRATE ENGINE: must use same Rochester carburetor and Speedway Motors
carburetor adaptor, part #135-3502G as claim engine. Maximum of two 0.100 inch
thick carburetor gaskets only. $50 cash claim on ALL carburetors, following
carburetor claim procedures and penalties (Refer to page 14).
only. Racing fuel allowed. No E85. No performance enhancing or scented
additives. Fuel must pass both dielectric meter and chemical tests (Refer to
www.imca.com for automatic penalties).
WEIGHT: No ballast
allowed. Any item deemed as ballast will be required to be replaced - i.e. fuel
cell straps, fuel cell cans, battery boxes, etc. No titanium, magnesium, carbon
fiber or tungsten products. No gun-drilled, tubular, hollow bolts or studs.
Steel fasteners only.
One 12 volt passenger car battery only, must be securely mounted between and
above frame rails, and positive terminal must be covered. Battery must be in
Marine type case if mounted in driver compartment. Starter must bolt in OEM
location. 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
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 HEI distributor only. Ford/Chrysler may use HEI distributor. No
billet distributors or crank triggers. Ignition rotor, cap, coil and module must
remain OEM-appearing. All engines MUST use unaltered MSD #8728 or #8727CT
rev-control and maximum 6,200 rpm chip for crate engine and maximum 7,000 rpm
chip for claim engine. (Refer to www.imca.com for automatic penalties.)
Rev-control must be mounted under hood on engine firewall and accessible for
inspection with rev limiter facing upward. No ignition boxes. All wiring must be
visible for inspection. OEM type alternator with internal regulator allowed. No
electronic traction control devices. (Refer to www.imca.com for automatic
SHAFT: All forward and reverse gears must be operational.
Must be unaltered OEM three or four speed, with minimum 10.5 inch steel/organic
single disc-type clutch and steel pressure plate assembly inside an
explosion-proof steel bellhousing - minimum 270 degrees around top of clutch and
flywheel area. No lightweight bellhousings. Hydraulic clutch release bearing
allowed. Steel unaltered flywheel only - 16 pound minimum - $150 fine if
Must be unaltered OEM, with unaltered OEM pump. Aluminum OEM bellhousing may be
replaced with aftermarket explosion-proof steel or aluminum bellhousing. Minimum
10 inch diameter torque converter containing a minimum of three quarts of fluid
- $150 fine if illegal. Torque converter must have a minimum 0.125 inch plug.
Must have approved scatter shield constructed of minimum 0.125 inch by three
inch steel, 270 degrees around flexplate. Flexplate must be full, unaltered OEM,
or OEM replacement. No bump starts allowed.
shaft: Steel drive shaft (minimum 2.5 inch diameter) and slip-yokes only.
Drive shaft must be painted white. 360-degree driveshaft loop required and must
be constructed of minimum 0.25 inch by two inch solid steel, or one inch tubing,
mounted six inches back from front U-joint.
Engine must be in OEM location. On GM metric frame, center of fuel pump must be
located minimum 1.75 inches in front of cross member (measured at frame). Ford
metric frames must have back of fuel pump in front of cross member. Frame and
cross member may not be altered for engine placement. Engine mount holes cannot
be removed or altered on block. Aftermarket steel engine mounts allowed. No
mid-plate allowed. Engine must be OEM appearing, must be able to be used in
conventional passenger car without alteration. GM with GM, Ford with Ford,
Chrysler with Chrysler. Minimum two-core radiator, must be mounted in front of
engine. Overflow tubes must be directed to ground. (2) Steel or aluminum V-belt
pulleys only. No electric fans, surge tanks or vacuum pumps.
ENGINE OPTIONS AND
SPECIFICATIONS: All cars utilizing the GM602 crate engine must clearly
display on both front roof posts the Chevrolet Performance emblem.
CRATE ENGINE: Must use
unaltered sealed GM #88869602 (Chevy cap seal), #88958602 or #19258602 crate
engine. All GM 602 Crate engines part
#88869602 with Chevy cap seals must have
IMCA Cable-Lok seals. Upon inspection, any different, altered or missing GM
seal bolts will result in automicatic 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 and pick-up, or with Kevko
pan #1087NRHw/ISP or IMCA87 and Kevko pick-up #1003-1 3/4. 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
CLAIM ENGINE: Any
American make engine allowed. BLOCK: OEM steel passenger vehicle production block only. No GM
Bowtie, Ford SVO or Chrysler W components allowed. GM approved block numbers
are: 10105123, 10066034, 3892657, 3914660, 3914678, 3932388, 3932386, 3956618,
3970000, 3970006, 3970010, 3970014, 10066033, 10066036, 10243880, 14010207,
14010209, 14010287, 14016376, 14016379, 10054727, 14088528, 14088548, 14088552,
14093638, 14101148. Stroke must match block. No 400 or larger cubic inch parts
allowed. Maximum 361 cubic inches (GM); 363 (Ford); 370 (Chrysler). 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. Maximum compression ratio is nine to one, no tolerance.
Compression ratio checked using Whistler and cubic inches checked using pump, OR
by visual inspection of part and/or casting numbers, pistons, etc (track option
which method is used). Flat top or dish pistons only, no gas ported pistons. 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. OEM or OEM cast appearing replacement steel rods only – GM 5.7 inch, 6
inch or GM Vortec rod part number 10108688 allowed. Cap screw allowed. No
splayed main caps. Conventional flat tappet cam and lifters only, cannot alter
lifter bores. OEM firing order cannot be changed (GM: 1-8-4-3-6-5-7-2). May use
oil restrictors. ‘Wet’ sump oiling system only. Steel oil pans only. Racing
oil pans allowed. Mandatory one inch inspection hole in all pans - no
obstructions to crank and rods. Accumulator allowed, must be mounted under hood.
CYLINDER HEADS: Steel only. Must be
unaltered approved OEM and minimum 76 cc combustion chamber (GM). Only GM OEM
approved head numbers are: 14079267, 3986336, 3986339, 3986339X, 3986388,
3932441, 376445, 3928454, 3932454, 3876487, 3973487, 3973487X, 3973493, 3951598,
468642, 330862, 333882, 3998920, 3998991, 3998993, 3998997, 3970126. Maximum
size valves on these heads are 2.02 inch intake and 1.60 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); Ford - no SVO heads; Chrysler - no W-2 heads, 360 cubic
inch heads only. No porting, polishing or unapproved alterations allowed to any
cylinder head or intake, disqualification and $250 fine if illegal. Guide
plates, screw-in shouldered studs (GM 0.375 inch max) and polylocks allowed. No
stud girdles. Steel roller tip rocker arms allowed. GM - 1.250 inch (± .015
tolerance) maximum O.D. valve spring, no beehive valve springs allowed. INTAKE:
Unaltered, approved OEM cast iron, low-rise, two barrel intake. 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. No
cooling lines allowed. Unaltered OEM type harmonic balancer only. OEM type steel
or aluminum water pumps only.
ENGINE CLAIM: Refer
to www.imca.com for claim eligibility requirements.
$550 cash claim on engine, $25 goes to wrecker for pulling engine
and $25 goes to official.
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.
exhaust manifold and pipes.
During engine claim, block and head numbers should be verified, heads, intake,
connecting rods and crankshaft should be visually inspected, exhaust manifold
must be removed to inspect heads, and one spark plug must be removed to check
flat top or dish pistons prior to transfer of engine to claiming driver. If, at
this time, engine is found illegal, claimed driver is disqualified and suspended
from all IMCA sanctioned events until such time as a $250 fine is paid, for
first offense, second offense penalties will be $500 fine and/or suspension.
Claimer then has option to accept or decline engine - if declined, driver is not
charged with claim.
STRUCTURE/PROCEDURES: Refer to www.imca.com.
EIRI: (Except in
rare instances) Decisions of officials are final and binding without exception.
In some cases, track safety rules may take precedence over IMCA rules - any
discrepancy between IMCA and track rules should be brought to the attention of
IMCA. Any rule changes or clarifications during the course of the year will be
amended at www.imca.com as well as published in Inside IMCA, the official
newsletter of IMCA, and will be considered as an official part of rules.
more information, call Dave Brenn at 785-307-8482 or Kirk Niehouse at
© 2019 IMCA. All rights reserved.
part of this publication may be reproduced, stored, or transmitted in any form,
without prior written permission.