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BoP Lab / Rules / GT1

GT1: rule changes

In our results from 2015-09-19 to 2026-09-28.

Wording removed by a change is shown struck through, as in the original. 56 changes, 46 other letters.

Changes made

Request TA Cup Cars Into GT1

#40250 from Scotty B White · Rule change · TB 26-08 (2026-08 Fastrack)

In GT1 Spec Lines, GT1 Cars – Porsche T/A Cup, change as follows:
Model: "T/A Porsche Cup"
Notes: "Max flat plate size 1-11/16 inch, must run T/A Porsche Cup rule set, Must have T/A Porsche Cup rule set in possession at
all race events."

Request TA Cup Cars Into GT1

#40250 from Scotty B White · Rule change · TB 26-07 (2026-07 Fastrack)

In GT1 Spec Lines, GT1 Cars – T/A Cup, classify T/A Porsche Cup as follows:
GT1 Cars – T/A Cup
Model Years Body Style Drive-
line
Wheel-
base (in)
Notes
T/A Porsche Cup Max flat plate size 1-11/16 inch, must run

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T/A Porsche Cup rule set, Must have T/A
Porsche Cup rule set in possession at all
race events.

Lamborghini Huracan Super Trofeo in GT1

#40288 from Tony Ave · Rule change · TB 26-07 (2026-07 Fastrack)

In GT1 Spec Lines, GT1 Cars - Lamborghini, classify Huracan Trofeo, Evo 2, Evo 3 as follows:
GT1 Cars - Lamborghini
Model Years Body Style Drive-
line
Wheel-
base (in)
Notes
Huracan Trofeo, Evo 2,

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Evo 3
All three (3) Classified to compete with original
Rule Spec's. All Three (3) allowed to compete at
"As Run weight".

Request for Huracan GT3 Evo Weight Reduction to 2950lbs

#40147 from Mike McAleenan · Rule change · TB 26-06 (2026-06 Fastrack)

In GT1-ST Spec Lines, Lamborghini Huracan GT3 (2019-), change weight as follows:
"3000 2950"

Reduce Weight for GM 275ci Carbureted V6s

#39713 from Cameron Wagner · Rule change · TB 26-03 (2026-03 Fastrack)

In GCR, Section 9.1.2.D.E.b., V-6 - up to 275 (4.5), change as follows:
"2345 2295"

Remove GT3U from GCR as it is now in STU

#39862 from SCCA Staff · Rule change · TB 26-03 (2026-03 Fastrack)

In GCR, change as follows:
9.1.2 Page 68: "GT-3U (GT3U)"
9.1.2.F page 320: "9.1.2.F. GT-2, 3, 3U LI TE CATEGORY SPECIFICATIONS"
9.1.3.9 Page 320: "9. All GT3U (Majors and Runoffs) cars using up to 15”x7” wheels limited to 225 section width tires shall run at
current GT3 race weight plus 225lbs. All Gt3U cars shall run a DOT approved tire with a maximum section width of 245. GT3U
cars are allowed optional 15”x9” wheels with a 1.5% weight addition or up to 18”x9” wheels with a 3.0% weight addition to the
total weight including the 225 lbs. TCR cars are ineligible for GT3/GT3U.
Table B: Alternate Vehicle and Engine Allowances Page 461:

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“Increase the minimum weight of all GT3/GT3U 2.0 liter unrestricted engines to +75 lbs. All GT3 cars running in STU must meet
the minimum ride height of 3.0” for the main frame rails not including rub blocks and a 2” minimum for the front spoiler and
splitter."

Request for Addition of Porsche 992.1 GT3 Cup into GT1

#39322 from Erik Madsen · Rule change · TB 26-02 (2026-02 Fastrack)

In 9.1.2. GT1 Spec Lines, add the following:
"992.1 GT3 Cup (2022-2025)
OEM ABS and Traction Control allowed. Porsche OEM RSR bumper and canards allowed. Any exhaust system may be utilized."

NSX Parity With Other GT3s Let Alone a GT1 Car

#39311 from Taz Harvey · Rule change · TB 26-01 (2026-01 Fastrack)

In GT1-ST, Acura NSX GT3 EVO 22, change Weight as follows:
"3100 3000"

RM 25-06 GT1 reclassify the Acura NSX GT3 EVO 22 to GT1-ST

#39101 from Club Racing Board · Rule change · TB 25-10 (2025-10 Fastrack)

IN GT1 reclassify the Acura NSX GT3 EVO 22 to GT1-ST as follows:
GT1 Approved Automobile List
Make/Model Wheelbase
ACURA
NSX GT3 EVO 22 103.5”
DOHC 4v per cylinder EFI Twin Turbo Crossflow V-6 Displacement 3500cc Bore and Stroke 91x90
MAX RPM 7500 MAX BOOST 2.1 bar Weight 3100 lbs
GT1-ST Maximum

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Displacement
Minimum
Weight Restrictor Notes
ACURA NSX GT3 EVO 22 3500cc 3100 Per FIA Homologation GT3-047

Correction to Limited prep LS Chevy engine for GT1

#38902 from Robert Logsdon · Rule change · TB 25-09 (2025-09 Fastrack)

In GCR, Section 9.1.2. GT1 Spec Lines, GT1 Approved Automobile List, LS1 engine allowed with stock intake, make the following
change:
"LS1 Limited Prep GT1 Motor Chevy LS Limited Prep Engine including LS1, LS2, LS3 and LS6."
"Pistons: Factory or aftermarket flat top pistons only, valve reliefs allowed, coatings allowed. Maximum compression ratio
11:1."

Request to Classify Acura NSX GT3 Evo 22

#37367 from Taz Harvey · Rule change · TB 25-03 (2025-03 Fastrack)

In GT1 Spec Lines, GT 1 Cars - ACURA, classify Acura NSX GT3 EVO 22 as follows:
GT 1 Cars - ACURA
Model Years Body Style Drive-
line
Wheel-
base (in)
Notes
Acura NSX GT3 EVO 22 N/A 2dr RWD 103.5 Ground Clearance 50mm

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In GT1 Spec Lines, GT 1 Engines - ACURA, classify Crossflow V-6 as follows:
GT 1 Engines - ACURA
Engine
Family
Engine Type Bore x

A specification table follows in the original; it is not shown here.

Addition of a limited prep LS Chevy engine for GT1

#37045 from Robert Logsdon · Rule change · TB 25-01 (2025-01 Fastrack)

In GCR, Section 9.1.2. GT1 Spec Lines, GT1 Approved Automobile List, LS1 V8 engine allowed with stock intake, add the
following:
"LS1 Limited Prep GT1 motor
2600 # with driver
Blocks : GM castings or aftermarket, no lightening, Max volume 383 cubic inches
Cylinder Heads: GM LS castings or aftermarket, stock valve angle, intake and exhaust ports must be in stock location, porting
and polishing allowed
Valves: No titanium valves, must be stock size for head part number

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Rockers: Factory 1.7 rockers only, aftermarket trunion mod allowed
Pushrods: Free
Intake manifold: stock EFI for variant used or GM 525 carb intake or Edelbrock carb variants ie: Performer RPM, Victor, Victor Jr.
or similar.
Camshaft: Hydraulic roller only, standard journal size, lift and duration free
Timing chain: single or double roller type only
water pump: stock or aftermarket in stock location
Harmonic dampener: SFI approved,
Pistons: Factory or aftermarket flat top pistons only, valve reliefs allowed, coatings allowed
Crankshaft: Factory or forged steel aftermarket, 50 lb min. weight
Rods: GM stock or aftermarket forged steel
Carburetor: one 4150 type 750 cfm max"

Correct language regarding OEM Areo Devices

#37137 from Christopher Childs · Rule change · TB 25-01 (2025-01 Fastrack)

In GCR, Section APPENDIX L. 2013 TA2 TECHNICAL REGULATIONS, B.2.c., change as follows:
"B. Aerodynamic Devices
2. Rear wing
c. The entire rear wing assembly, including the end plates and any Gurney flap, shall be mounted level
with, or below, the peak of the roof. OEM aerodynamic devices do not need to adhere to the height rule."

A specification table follows in the original; it is not shown here.

GT1-ST Adjustments

#37481 from Grand Touring Committee · Rule change · TB 25-01 (2025-01 Fastrack)

In GT1-ST SPEC LINES, change as follows:
Aston Martin Vantage GT3 (2012) :
Restrictor: "2 x 41.5mm"
Audi R8 LMS Ultra GT3 (10-14) :
Restrictor: "2 x 49mm"
BMW Z4 GT3 (10-13):
Restrictor: "70mm"
Chevrolet Corvette C8 (20-):

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Restrictor: "71mm- Flat Plate"
Dodge Viper GT3R (2012-):
Restrictor: "2 x 40mm"
Dodge Viper, incl Comp Coupe, ACR/ACR-X Max Displacement 8400, Weight 3200:
Restrictor: "68mm flat plate"
Ferrari 458 GT3 (2011-):
Restrictor: "2 x 43mm"
Lamborghini Gallardo GT3 (2013):
Restrictor: "2 x 47mm"
Lamborghini Huracan GT3 EVO(1) (2018-):
Restrictor: "2 X39mm"
McLaren MP12C GT3 (2013-):
Restrictor: "2 x 36mm 1.50 bar"
Lamborghini Huracan GT3 (2019-):
Restrictor: "2 x 40 mm"
McLaren MP12C GT3 (2013-):
Restrictor: "2 x 40 mm"
Mercedes Benz SLS GT3 (2011-):
Restrictor: "2 x 36 mm"
Porsche 991 GT3-R (2016):
Restrictor: "(2) 35 mm"
Porsche 997 GT3 R (2013-):
Restrictor: "65mm"

Lamborghini Huracan GT3 Evo Restrictor Help

#36254 from Michael McAleenan · Rule change · TB 24-12 (2024-12 Fastrack)

In GT1-ST Spec Lines, Lamborghini Huracan GT3 EVO(1) (2018-), change Restrictor as follows:
"2 X 39mmUnrestricted"
In GT1-ST Spec Lines, Lamborghini Huracan GT3 (2019-), change Restrictor as follows:
"52mm Unrestricted"

Request to Classify Mazda 26B Engine

#36230 from Wayne Graham · Rule change · TB 24-09 (2024-09 Fastrack)

In GT1 Spec Lines, GT1 Approved Automobile List, Mazda, add the following:
"(Effective 11/1/2024) 26B engine = 2850 lbs."

Request for Spec Line 1010 Reconsideration

#35009 from Kristofer Olson · Rule change · TB 24-05 (2024-05 Fastrack)

In GT2-ST Spec Lines, Acura NSX, change as follows:
Minimum Weight: "2700 3000"
Restrictor: "43 45mm TIR"

Camaro 1993- and 2010-

#35652 from John Bodnar · Rule change · TB 24-05 (2024-05 Fastrack)

In GCR, Section 9.1.2.E.1.b.3., change as follows:
"Camaro (1993-2002)"

Rear Blade Spoiler Clarification

#35261 from Butch Kummer · Rule change · TB 24-02 (2024-01 Fastrack)

In GCR Section 9.1.2.G (GTA Category Specifications), change as follows:
“9.1.2.G.III.I
The single-plane rear spoiler must be mounted at an angel angle from 50 to 75 degrees (perpendicular to the ground
being 90 degrees) and may not extend beyond the rear bumper when viewed from directly above the rear
bumper. Spoilers must be a minimum of .063 aluminum or Lexan and may vary in overall height to match the contours
of the bodywork. The rear spoiler dimensions shall not exceed 59.0 inches wide by 5.0 inches in height, (measured on
the material surface) , or 295.0 square inches total surface area. Braces to prevent spoiler deflection are allowed, but
may serve no other purpose.”

GT Direct Injection allowance and rules

#35437 from Grand Touring Committee · Rule change · TB 24-02 (2024-01 Fastrack)

In GCR, Section 9.1.2.F.7.5.E. change as follows:
“Direct Injection is not permitted only if it came OE and must be installed using only OE high pressure pump(s), hard and
soft hoses and injectors.”

GT2/3 remove Direction Injection not allowed in Spec line notes

#35439 from Grand Touring Committee · Rule change · TB 24-02 (2024-02 Fastrack)

In GT2/3 modify Spec Line notes as follows:
GT2:
Nissan: “Direct Injection not permitted, may be used per 9.1.2.F.7.5.E.”
GT3:
Mazda: “Direct Injection not permitted, may be used per 9.1.2.F.7.5.E.”
Mitsubishi 4G93: “Direct Injection not permitted, may be used per 9.1.2.F.7.5.E. ”
Nissan QR25DE/DD 1988cc: “Direct Injection not permitted, may be used per 9.1.2.F.7.5.E.”
Nissan QE25DE/DD 2489cc: “Direct Injection not permitted, may be used per 9.1.2.F.7.5.E.”

Request for Acceptance of Lamborghini Huracan GT3 in GT1-ST

#34929 from Michael McAleenan · Rule change · TB 24-01 (2024-01 Fastrack)

In GT1-ST Spec Lines, classify Lamborghini Huracan GT3 EVO(1) (2018-) as follows:
GT1-ST Maximum Displacement Minimum Weight Restrictor Notes
Lamborghini Huracan
GT3 EVO(1)
(2018-)
5204 3000 2 X39mm Per FIA Homologation
GT3-040
In GT1-ST Spec Lines, classify Lamborghini Huracan GT3 (2019-) as follows:

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GT1-ST Maximum Displacement Minimum Weight Restrictor Notes
Lamborghini
Huracan GT3
2019-
5204 3100 52mm Per FIA Homologation
GT3-040

Cylinder heads

#35040 from Pater Mumford · Rule change · TB 24-01 (2024-01 Fastrack)

In GCR, Section 9.1.2.D.1.e.3., add at the end of section add the follows:
"Trick Flow Specialties Ultra 18 Degree GM Cylinder Head assembly Part #TFS-3181T001-CO1 is allowed."

Errors in GTCS Headings and Use of the Terms Category and ClassChange existing GTL and GTA Rules

#34453 from David Gomberg · Rule change · TB 23-12 (2023-12 Fastrack)

from the current (or before) Table of Contents (TOC), to what is shown in the after TOC.
GTL spec lines will now be contiguous with GT2 and 3 spec lines.
GTA category and spec lines will be moved and renumbered behind GTL. GTA Section will not change but page numbers will, (as
shown in Red italics).
9.1.2.F. GT-2, 3, LITE Category Specifications 314
GT2 Cars 327
GT2/ST 341
GT3 Cars 348

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GTL Cars 364
GTA Cars 377
P2 Engine Table B.1
2010 and older
Stock Kawasaki
38.5mm
minimum width 52 inches. AMAC-AM5:
minimum width 54 inches.
P2 Engine Table B.1
2008 and older
Stock Engine Suzuki,
Yamaha,
Honda, BMW
38.5mm
P2 Engine Table B.2 Not required
P2 Engine Table B.3 38.5mm
Modified Engine
950 lbs.
1005cc max
P2 Engine Table B.1 37mm
P2 Engine Table B.2 Not required
P2 Engine Table B.3 39mm
Stock Engine
1050 lbs.

Please classify Fields Cardinal V8

#33784 from James Rogersn · Rule change · TB 23-05 (2023-05 Fastrack)

In GT Spec Lines, GT1 Cars - Fields Cardinal, classify Fields Cardinal V8 as follows:
GT1 Cars – Fields Cardinal
Model Years Body Style Drive-
line
Wheel-
base (in)
Notes
Fields Cardinal V8 2023 2 Dr. RWD 92.0 Roll Cage MUST be modified to comply with

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GCR Section 9.4.
In GT Spec Lines, GT1Engines - classify Ford V8 as follows:
GT1 Engines - Ford
Engine
Family
Engine Type Bore x

A specification table follows in the original; it is not shown here.

Mercedes AMG GT3 Notes

#33804 from Gary D'Abate · Rule change · TB 23-04 (2023-04 Fastrack)

In GT1-ST Spec Lines, Mercedes Benz AMG GT3 (16-19), change Notes as follows:
"Car must be prepared to per its FIA GT3 homologation. except as specified differently within the GT1 class rules."

Sequential Transmission Weight Penalty

#33503 from Richard Grant · Rule change · TB 23-02 (2023-02 Fastrack)

In GCR 9.1.2 Grand Touring 1 (GT1) Specifications, Section 9.1.2.D.4.b.2, change as follows:
"Sequential shifting transmissions are permitted with a 50 25lb. weight penalty."

GT1 Porsche 992

#33730 from Grand Touring Committee · Rule change · TB 23-02 (2023-02 Fastrack)

In GT1-ST Spec Lines, Cars - Porsche, classify Porsche 992 GT3 Cup Car as follows:
GT1-ST Maximum
Displacement
Minimum
Weight Restrictor Notes
Porsche 992 GT3 Cup 3997 2950 Car must be prepared in accordance with
the appropriate model/year Porsche 992
factory service manual. Factory (OEM

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manufactured) Lexan front windows
allowed as delivered. ABS permitted.

GT2 (TA2)/GTA Part Number Update

#33315 from Butch Kummer · Rule change · TB 22-12 (2022-12 Fastrack)

In GCR Appendix L-TA2 rules, Addendum A, change A.2. as follows:
"The throttle body must be either a GM 90mm, electronic, part #1257 → 0790, or Edelbrock 90mm, mechanical, part 33869 or
#3870."
In GTA, GCR Section 9.1.2.G.3., change as follows:
"The throttle body must be either a GM 90mm, electronic, part #1257 → 0790, or Edelbrock 90mm, mechanical, part 33869 or
#3870."

Request to Reduce Trans Am Bodywork Weight Penalty

#33331 from David Pintaric · Rule change · TB 22-12 (2022-12 Fastrack)

In Grand Touring 1 (GT1) Specifications, GCR Section 9.1.2.D.8.a.7., change as follows:
"Current Trans Am bodywork is allowed with a 100 75lb. weight penalty."

Request for Reduction in FR9 Weight Penalty

#33332 from David Pintaric · Rule change · TB 22-12 (2022-12 Fastrack)

In GT1 (GT1) Specifications, GCR Section 9.1.2.E.1.b.1., change as follows:
"Chevrolet/GM - RO7 + 50 25 lbs.
Ford - FR9 + 50 25 lbs.
Dodge - R7 + 50 25lbs."

Tail lights on all GT category race cars.

#32799 from John Mills · Rule change · TB 22-09 (2022-09 Fastrack)

In GT, GCR Section 9.1.2.F.7.a.6:
"Glass and/or plastic headlights, front parking lights, front signal lights, lenses, and bulbs shall be removed. Headlight openings
shall be covered with a wire mesh screen or panel having the same contour as the original lens, mounted so that the headlight
bezel/rim remains in place, maintaining the standard appearance of the Production automobile. Side marker light assemblies
shall be removed and the resulting openings covered with a plate whose dimensions do not exceed those of the original parts;
side marker lights that are an integral part of the taillight assembly cannot be removed. Other lighting parts and operating
mechanisms may be removed. In the case of pop-up headlights, the entire assembly may be removed and the opening covered
with a screen or plate (as above, without the headlight bezel/rim requirement) which provides a stock appearance. It is not

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permitted to relocate the standard headlight, parking light, signal light, etc., openings. Traditional GT cars only. Not allowed with
any "Spec Car, GT2-ST, or any other added non Traditional GT car. Taillights shall be in the original location and shall may be the
original style/type of taillight for the make, model, and year of car. A rear body panel having the same contour as the original
lens area and in the original location, may be fitted with a tail-light graphic of the original style/type frame/lens adhered to it. If
side marker lights are an integral part of the tail-light assembly they must be represented by the panel graphic. These
panel/graphics shall have a functioning red LED lamp assembly fitted through them on both sides of the car to serve as brake
lights. A 15-watt or equivalent rain light may be included with-in this LED assembly or may be a separately mounted single or
dual LED assembly."

GT-1/TransAm rules simplification/modernizing

#32763 from Tony Ave · Rule change · TB 22-08 (2022-08 Fastrack)

In GT1 Category Specifications, GCR Section 9.1.2.D.8.a. add the following:
"7. Current Trans Am bodywork is allowed with a 100lb. weight penalty."

Mercedes Benz AMG GT3 in GT1

#31883 from THOMAS HERB · Rule change · TB 22-03 (2022-03 Fastrack)

In GT1 Cars - Mercedes Benz, classify Mercedes Benz AMG GT3 as follows:
GT1 Cars – MERCEDES BENZ
Model Years Body Style Drive-

A specification table follows in the original; it is not shown here.

Wheel Widths

#32205 from Club Racing Board · Rule change · TB 22-03 (2022-03 Fastrack)

In GT1, GCR section 9.1.2.D.7.a., change as follows and renumber:
"1. Wheels shall be made of steel, aluminum, magnesium, or a combination thereof. Multi-piece wheels shall utilize mechanical
fasteners (bolts, rivets, etc.) for assembly.
2. Wheels may be thirteen (13), fourteen (14), fifteen (15), sixteen (16), seventeen (17), or eighteen (18) inches in diameter, but
all four (4) wheels shall be of the same diameter. Use of eighteen (18) inches wheels must add 50 lb. weight penalty.
3. 1.Wheels shall have a maximum width of twelve (12) inches in the front and thirteen (13) inches in the rear. 18” tires shall
have thirteen (13) MAX inches in the front and fourteen (14) MAX inches in the rear."

Wheel Widths

#31844 from Richard Grant · Rule change · TB 22-02 (2022-02 Fastrack)

In GCR, Section 9.1.2.D.7.a., change as follows:
"2. Wheels may be thirteen (13), fourteen (14), fifteen (15), or sixteen (16), seventeen (17) or eighteen (18) inches in diameter,
but all four (4) wheels shall be the same diameter. Use of eighteen (18) inches wheels must add 50 lb. weight penalty.
3. Wheels shall have a maximum width of twelve (12) inches in the front and thirteen (13) inches in the rear. 18" tires shall have
thirteen (13) in the front and fourteen (14) inches in the rear ."
SP - Tony A to consolidate response.

Request car classification

#31032 from Bryan Scheible · Rule change · TB 21-10 (2021-10 Fastrack)

In GT3 Engines - VOLKSWAGEN, classify Fun Cup Beetle EVO3 as follows:
GT3 Engines - VOLKSWAGON

A specification table follows in the original; it is not shown here.

Request to Update GTA Obsolete Part Numbers

#30615 from Butch Kummer · Rule change · TB 21-08 (2021-08 Fastrack)

In GCR, Section 9.1.2.G.16., change as follows:
"0-80541-1 0-80541-2"
In GCR, Section 9.1.2.G., Appendix Z 5.a. change as follows:
"0-80541-1 0-80541-2"
In GCR, TA2 Appendix B.3.4, change as follows:
"#6010 6014X"

GT Category Wording

#29193 from Randall Smart · Rule change · TB 20-09 (2020-09 Fastrack)

In GCR, Section 9.1.2.F.3.5., Specifications, change as follows:
"Turbocharging/supercharging is not permitted. unless listed on the spec line."

Request to Allow New Trans Am Legal Engines in GT1

#29002 from Tony Ave · Rule change · TB 20-08 (2020-08 Fastrack)

In GT1, Weight Chart for GT-1, add to chart as follows:
"Trans Am spec:
Chevrolet/GM - R07 + 50 lbs.
Ford - FR9 + 50 lbs.
Dodge - R7 + 50 lbs."

TA2 Gurney flap wicker clarification

#28874 from SCCA Staff · Rule change · TB 20-07 (2020-07 Fastrack)

In Appendix L TA2 Rules, clarify wording as follows:
“4.8.4.1.10.1.1: The maximum height of the wing, including end plates and wicker Gurney flap, can be
no greater than the highest point on the roof. The roof may not be altered or pushed up to increase its
height.”
“4.8.4.1.10.1.5: The wing end plates must fit within a rectangle measuring 11.00 inches long by 4.00
inches tall. All wing elements, including the wicker bill Gurney flap, must be kept within the profile of the
end plates. The endplates must be mounted parallel to the vehicle centerline, and must be
perpendicular to the ground. Endplates must be flat, with no curvature or Gurney tabs flap. “

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“4.8.4.1.10.1.6: A wicker bill (Gurney) Gurney flap may be added to the wing element. It must be a
uniform shape across the complete width of the wing. No air may pass between the wicker bill Gurney
flap and the wing. It must form a 90 degree angle with the wing surface. The size of the wicker bill
Gurney flap cannot exceed 0.50 inch high as measured from the wing surface. The thickness of the
wicker Gurney flap material must be 0.625 inch.”
“4.8.4.1.10.2.4: The dog leg style Howe endplates must be used without modification. All wing
elements, including the wicker bill Gurney flap, must be kept within the profile of the end plates. The
endplates must be mounted parallel to the vehicle centerline, and must be perpendicular to the ground.
Endplates must be flat, with no curvature or Gurney tabs flap. “
“4.8.4.1.10.2.5: A wicker bill (Gurney) Gurney flap may be added to the upper wing element. It must be
a uniform shape across the complete width of the wing. No air may pass between the wicker bill Gurney
flap and the wing. It must form a 90 degree angle with the wing surface. The size of the wicker bill
Gurney flap cannot exceed 0.375 inch. The thickness of the wicker bill Gurney flap must be 0.0625
inches.”
“4.8.4.2.10.3.4: The dog leg style Howe endplates must be used without modification. All wing
elements, including the wicker bill Gurney flap, must be kept within the profile of the end plates. The
endplates must be mounted parallel to the vehicle centerline, and must be perpendicular to the ground.
Endplates must be flat, with no curvature or Gurney tabs flap. “
“4.8.4.2.10.3.5: A wicker bill (Gurney flap) Gurney flap may be added to the upper wing element. It must
be a uniform shape across the complete width of the wing, and must be kept within the profile of the
end plates. It must form a 90 degree angle with the wing surface. The size of the wicker bill Gurney flap
cannot exceed 0.375 inch high as measured from the wing surface. The thickness of the wicker Gurney
flap material must be 0.0625 inch.”

STO Gurney flap wicker clarification

#28883 from SCCA Staff · Rule change · TB 20-07 (2020-07 Fastrack)

In Appendix K, STO, clarify wording as follows:
B.2.a.: "Wings shall be a single element with a maximum chord length of 12.00 inches, including any
wicker Gurney flap."
B.2.c.: "The entire rear wing assembly, including the end plates and any wicker Gurney flap, shall be
mounted level with, or below, the peak of the roof."

GT1 Gurney flap wicker clarification

#28886 from SCCA Staff · Rule change · TB 20-07 (2020-07 Fastrack)

In GT1 Specifications, section D, clarify wording as follows:
"The use of fences, end rails, Gurney lips flaps, wickerbills, or other forward facing lips or aerodynamic
devices is prohibited."
In GT1 Specifications, section E, clarify wording as follows:
"A maximum 0.50 inch Gurney tab flap is allowed at the trailing edge of the wing element."
"Endplates must be flat, with no curvature or Gurney tabs flaps. The maximum width of the entire wing
assembly (wing element, endplates, Gurney tab flap, and mounting hardware) is 72.00 inches. In
keeping in line with ˜Trans Am body work is legal in GT1”, An alternate rear wing of 12” average chord

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length and maximum 72” long is allowed, with a maximum 1/2” tall wicker Gurney flap, additionally
endplates having a maximum size of 100 square inches."

GT Gurney flap wicker clarification

#28909 from SCCA Staff · Rule change · TB 20-07 (2020-07 Fastrack)

In GT, GCR section 9.1.2.F.7.b.12., clarify Gurney flap as follows:
"D. The use of fences, end rails, Gurney flaps, wickerbills,or other forward facing lips or aerodynamic
devices is prohibited."
"E. A maximum 0.50 inch Gurney tab flap is allowed at the trailing edge of the wing element. The tab
must be mounted 90 degrees to the upper wing surface. No air may pass between the tab and the wing.
The endplates must be mounted parallel to the vehicle centerline, and must be perpendicular to the
ground. Endplates must be flat, with no curvature or Gurney tabs flaps."
"GT3: The maximum width of the entire wing assembly (wing element, endplates, Gurney tab flap and

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mounting hardware) is 64.00 inches, but no wider than the rear body width including fender flares."
In GT, GCR section 9.1.2.F.7.b.13., clarify Gurney flap as follows:
"A. Endplates must be flat, with no curvature or Gurney tabs flap. A maximum 0.5-inch wicker-
bill Gurney flap may be employed."
In GT, GCR section 9.1.2.F.7.b.15.D., clarify Gurney flap as follows:
"2. Rear Wing: Wings shall be a single element with a maximum chord length of 12.00 inches, including
any wicker Gurney flap."
"4. The entire rear wing assembly, including the end plates and any wicker Gurney flap, shall be
mounted level with, or below, the peak of the roof."

Windshield Clips

#27323 from Todd Oppermann · Rule change · TB 20-02 (2020-02 Fastrack)

In GCR section 9.1.2.F.6.c.1, add as follows:
Alternatively, the bottom may be captured in a channel.
"No clips or straps are required if bonded-glass factory windshields and/or rear windows are attached to
chassis per original specifications (i.e., glass-bonding adhesive).”

Request to classify the Ford Coyote 3rd Gen OEM

#27146 from Cheyne Daggett · Rule change · TB 19-09 (2019-09 Fastrack)

Effective 01/01/2020, In GT2/ST, Ford 5.0L “Coyote” engine, add to the notes as follows:
““Boss” intake manifold permitted. Ford Coyote 3rd Gen OEM (2018-2019) Part # M-6007-M-50C
@3200lbs."

Request Factory Five Daytona coupe classification

#26308 from Andrew Wickline · Rule change · TB 20-01 (2020-01 Fastrack)

In GTX - MISC., Classify and add as follows:
GTX – MISC.
Make Model Engine Restrictor
mm Weight (lbs) Notes
Factory Five Type 65
Coupe R
Ford
302/351

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NA 2600
Factory Five Type 65

A specification table follows in the original; it is not shown here.

Request to Adjust Transmission Penalty

#27750 from J Richard Grant · Rule change · TB 20-01 (2020-01 Fastrack)

In GT1 Specifications, section 9.1.2.D.4.b.2., make change as follows:
"Sequential shifting transmissions are permitted with a 75 50 lb. weight penalty."

Request to Reduce Additional Weight for 18

#27751 from Matthew Miller · Rule change · TB 20-01 (2020-01 Fastrack)

In GT1 Specifications, section 9.1.2.D.7.a.5., make change as follows:
"For cars not specified to allow 18 inch wheels, 18 inch wheels permitted with a 100 50 pound weight
penalty."

Request for Five Star Nascar Compliant Bodywork

#27756 from Tim Adolphson · Rule change · TB 20-01 (2020-01 Fastrack)

In GT1 Spec Lines, 9.1.2.c, General Motors Corporation, add the following:
"5 Star NASCAR Camaro (2018-) body allowed"

Request to classify Porsche 944/968

#26242 from Marvin Epps · Rule change · TB 19-09 (2019-09 Fastrack)

In GT1, classify the 944/968 as follows:
“944/968
94.5”
2981cc 4, DOHC, Bore x Stroke (mm) 104.0 x 88.0, Aluminum crossflow, Unrestricted, Twin (2) Turbo.
Weight = 2585”

Clarify Trans Am Legal Bodywork and Wing

#26953 from Tony Ave · Rule change · TB 19-07 (2019-07 Fastrack)

Effective 6-01-2019, In GT1, GCR section 9.1.2.D.8.k.2.E, make changes as follows:
"In keeping in line with ˜Trans Am bodywork is legal in GT1", An alternate rear wing of
12" average chord length and maximum 72"ÂÂÂÂÂÂ
 long is allowed, with a maximum
1/2" tall wicker, additionally endplates having a maximum size of 100 square inches.
There is no weight penalty for this wing."
Effective 6-01-2019, In GT1, GCR section 9.1.2.D.8.n.1.B.2, make changes as follows:
"In keeping in line with ˜Trans Am bodywork is legal in GT1", A front undertray is

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allowed, as shown in 13.15.7 of the Trans Am racing rulebook, with a 50 pound penalty."

Request GTX Fuel injection for previous GT-1 tube frame cars

#26141 from Michael Major · Rule change · TB 19-05 (2019-05 Fastrack)

In GTX, GCR section 9.1.2.H.I.3, add throttle body size as follows:
“GTX tube frame cars may install fuel injection system, maximum throttle body
size TBD 90mm.”

Request to Classify Ligier JS2 R

#26535 from Jeffery Smisek · Rule change · TB 19-05 (2019-05 Fastrack)

In GTX, classify the Ligier JS2 R as follows:
GTX- MISCModel Homologation Model Restrictor Weight Notes

Request Ride Height Clarification

#26600 from SCCA Staff · Rule change · TB 19-04 (2019-04 Fastrack)

In GT1, GCR section 9.1.2.D.5.a.1, omit ride height and re-number section as follows:
“a. Ride Height
1. No part of the car to the rear of the front tire opening, including the exhaust, may touch the
ground when two (2) tires on the same side of the vehicle are deflated.”
In GT-2, 3, LITE, GCR section 9.1.2.F.7.b, remove and re-number section as follows:
“3. No part of the bodywork or chassis, to the rear of the front wheel opening, shall touch the
ground when both tires on the same side of the car are deflated.”

GTX Homologation table update

#26034 from Club Racing Board · Rule change · TB 19-01 (2019-01 Fastrack)

In GTX, FIA GT3, classify the Audi R8, BMW Z4, and Ferrari 488 Challenge as follows:
FIA GT3 -
Make Homologation Model Restrictor
mm Weight (lbs) Notes
Acura GT3- 047 NSX (2) 35 TIR 3015
Aston Martin GT3-O32 Vantage (2) 41.5 2980
Audi GT3-017 R8 (2) 40 TIR 2900
Audi GT3-038 R8 LMS (2) 39 TIR 2980

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Bentley GT3-035 Continental (2) 38 TIR 3070
BMW GT3-043 M6 (2) 34 TIR TBD
BMW GT3-023 Z4 70 2800
Chevrolet GT3-045 Corvette C7 52 3070
Dodge GT3-036 Viper (2) 39 3120
Ferrari GT3-029 458 (2) 40 3025
Ferrari GT3-044 488 (2) 35 TIR 3025
Lamborghini GT3-040 Huracan (2) 39 TIR 3015
Mclaren GT3-037 650S (2) 36 TIR 2915
Mercedes GT3-042 AMG GT (2) 34.5 TIR 3090
Porsche GT3-041 991 (2) 41.5 2960
Nissan GT3-030 GT-R (2) 40 TIR 3050

A specification table follows in the original; it is not shown here.

Other letters

Classification and Approval of CEI Trans Am Cup Cars into GT1

#40264 from Chris Rhom · No action required · Minutes (2026-07 Fastrack)

Please see letter #40250 in current Fastrack.

Clarification for LS1 Limited Prep GT1 Motor Rules

#38516 from Daniel Speer · No action required · Minutes (2025-08 Fastrack)

Thank you for your letter. In answer to your questions:
1. Any mass-produced aftermarket intake manifold is permitted.
2. Intake manifold with 90mm OEM throttle body is permitted
3. Any mass-produced aftermarket cylinder heads is permitted with no valve angle modifications.

FIA GT3 Classing

#37291 from Scotty B White · Taken care of · Minutes (2025-01 Fastrack)

Thank you for your letter. Please see the CRB response to letter #36254 in December Fastrack.

GT1 Alternate Engine Combination for Cost Reduction

#36850 from Daniel Speer · No action required · Minutes (2025-01 Fastrack)

Thank you for your letter. Please see the CRB response to letter #37045 in current Fastrack.

Follow Up to Letter # 36254 - Info Supporting Restrictor Removal

#36269 from Michael E McAleenan · Taken care of · Minutes (2024-12 Fastrack)

Thank you for your letter, please see the CRB's response to your earlier letter #36254 in current Fastrack.

GT Committee Application and Resume

#35118 from Ken Gassin · Member feedback requested · Minutes (2024-01 Fastrack)

Thank you for your resume. The GTAC would like to accept your offer to join the GT Advisory Committee.
DATE: December 20, 2023

Follow-up on Letter 34453

#35170 from David Gomberg · Taken care of · Minutes (2023-12 Fastrack)

Thank you for your letter. Please see letter #34453 in current Fastrack.

Makes no sense

#34713 from Philip Di Pippo · No action required · Minutes (2023-11 Fastrack)

Thank you for your letter. Please see letter #34815 in current Fastrack.

#33594 - Weight Clarification

#33820 from Jeremy Schwarz · No action required · Minutes (2023-04 Fastrack)

Thank you for your letter. Here is an example:
2780 base
+ 75 lbs. total for T/A aero adds (this includes a tunneled nose)
+ 50 lbs. for 18.0" wheels
+ 25 lbs. for sequential transmission
+ 25 lbs. for FR9 or RO7 engines
Total in this configuration would be 2955 lbs.

Weight Penalty - TA

#33594 from Jeremy Schwarz · No action required · Minutes (2023-02 Fastrack)

Thank you for your letter. You are incorrect in your interpretation. If you a competitor decides to add a front nose diffuser to an
otherwise GT1 compliant body, it's a 50 lb. weight penalty. If a competitor chooses to add anything else that T/A now allows
aero-wise, either in addition to, or instead of the nose diffuser, it's a 100 lb. weight penalty.

Trans Am Body Weight Penalty

#33433 from Richard Grant · No action required · Minutes (2023-01 Fastrack)

Thank you for your letter. Please see letter #33332 in December Fastrack.

Supplement and Correction to letter #32699 (Ginetta G56)

#32702 from Philip Di Pippo · No action required · Minutes (2022-11 Fastrack)

Thank you for your letter. Please see letter #33076 in September 2022 Fastrack.

Response and Further Request Following Letter 32514 (Ginetta G56)

#32699 from Philip Di Pippo · No action required · Minutes (2022-10 Fastrack)

Thank you for your letter. Please see letter #33076 in September 2022 Fastrack.

Engine Placement

#31272 from Robert Lewis · No action required · Minutes (2021-11 Fastrack)

Thank you for your letter. Your two assumptions are correct. For the answer to your question please see GCR page #146
Appendix G, item 4. Measuring Track.

Request aftermarket ECU allowance

#30593 from Nathan McBride · No action required · Minutes (2021-06 Fastrack)

Thank you for your letter. All GT2 and ST cars with the exception of various GT2 "spec" classifications can already have
an ECU of their choice!

Request for Clarification on Bridge Porting for Rotary

#26004 from Luis Rivera · Taken care of · Minutes (2021-01 Fastrack)

Thank you for your letter. Please refer to Technical Forms and Downloads on the SCCA website.

Resume for GT

#28181 from Samuel Fouse · Member feedback requested · Minutes (2020-03 Fastrack)

Thank you for your resume. We will keep your resume on file for future needs on the GTAC AdCom.
DATE: February 20, 2020

Request for reduction in weight penalty for 18

#27761 from David Pintaric · No action required · Minutes (2020-01 Fastrack)

Thank you for your letter. Please see the response to letter #27751 in this Fastrack's Technical Bulletin.

Request sequential transmission weight penalty reduction

#27760 from David Pintaric · No action required · Minutes (2020-01 Fastrack)

Thank you for your letter. Please see the response to letter #27750 in this Fastrack's Technical Bulletin.

Request to Reduce Weight Added for Use of Sequential Transmission

#27752 from Matthew Miller · No action required · Minutes (2020-01 Fastrack)

Thank you for your letter. Please see the response to letter #27750 in this Fastrack's Technical Bulletin.

Request for Splitter Clarification, Driver/Owner GT-1 #89 NYR

#27048 from Scott Quaile · Taken care of · Minutes (2019-08 Fastrack)

Thank you for your letter. Please see July Fastrack.

Request GT1-ST classification for Ferrari Challenge 488

#26163 from david mead · No action required · Minutes (2019-03 Fastrack)

Thank you for your letter, the GT1-ST was already classified in GTX.

Request to Classify Ferrari 488 Challenge Car

#25957 from Matt Jensen · Taken care of · Minutes (2019-01 Fastrack)

Thank you for your request. This car is being classified in GTX in letter #26034, Technical
Bulletin.

Request to Clarify Audi R8 Lifespan

#25824 from Jason Morris · No action required · Minutes (2019-01 Fastrack)

Thank you for your request. There is no sunset date as long as someone continues to race
that car.

Request to Classify 2016+ Shelby 5.2 350GTR

#23944 from Scotty B White · Taken care of · Minutes (2019-01 Fastrack)

Thank you for your request. Please see the response to letter #21466, Technical Bulletin.