GT SUMMIT PROPOSAL
SCCA GT Summit Meeting
Denver, Colorado
December 11-12, 1999

Member Input Request:
Inputs on the following proposed changes to the GT rules and specifications are solicited from all interested members, with input strongly desired from current GT competitors.
It is intended to have these changes, as modified due to member input, approved by the Competition Board in time to submit to the Board of Directors at their normally scheduled December, 2000 meeting, for implementation effective 1/1/2002.
While inputs are desired on all parts of this proposal, the proposed future changes to GT1 maximum engine sizes and GT1,2, and 3 wheel sizes are still under significant debate and input is specifically requested on these issues.
Address all comments to the SCCA Club Racing Department, 9033 E Easter Place, Englewood, CO 80112; Fax: (303)694-7391; E-mail: ClubRacing@scca.org. Please include your GT racing background with your comments.
Attending Representatives:
· SCCA, Inc.: Dennis Dean, Howard Duncan, Patc Henry
· SCCA Competition Board: Phil Creighton, Tom Howen
· SCCA GT Advisory Committee: Hubert Duprez, Robert Dowie, Peter Zekert, David Finch, Duane Davis
· Toyota: Tom O'Connor, Don Preston
· Nissan: Frank Honsowetz, Ron Johnson
· Mazda: Steve Sanders, Daryl Drummond
· BMW: T.C. Kline
This meeting was called to address improvements to the current GT rules to better position the category for the coming years, particularly from the perspective of manufacturer support. This support is believed necessary for the long term viability of the category, in view of the relatively high technology and costs of the category. Several fundamental principles were agreed upon by the participants during the course of the meeting, which are described below.
There was a strong desire on the part of all concerned to take the politics out of GT category classifications and to base future classifications on a sound, scientific-based system.
The manufacturer representatives were asked to participate directly in these discussions, in addition to the member representatives present in the form of the Competition Board members and the GT Advisory Committee, in recognition of the manufacturer involvement envisioned in the guiding principles of the category, as outline in the GTCS. Specifically, all concerned are reminded of the following GTCS wording:
"The GT Category is intended to provide the membership and interested manufacturers with the opportunity to compete in purpose built, highly modified replicas of series produced automobiles. . . . the intent of these rules to allow modifications useful and necessary in the construction and preparation of an extremely high performance road racing vehicle. It is understood that such a vehicle can be updated and/or changed from marque-to-marque, based on member interest and manufacturer incentive."
1. Fundamental Guiding Principles:
a. The current GT specifications will be used as the baseline for any future modifications, as well as these proposals.
b. The desire is to race contemporary models against contemporary models
c. A Scientific weight and displacement rule is needed to get away from the current classification of individual cars.
d. Weight variation within a class will be minimized.
e. GT1, 2, 3 should be treated in a like manner using the general concept of the current GT1 rules as a framework, but not necessarily linked to the Trans-Am rules.
f. GT4, 5 should be treated in a like manner, but different than the big bore classes. The intent is keep GT4,5 much as they currently are.
g. Once, updated, rules should be stable, which would allow manufacturers long term usage of a particular engine.
h. "Current Bodywork" defined as being models which are currently being produced or have been out of production for no more than three years, somewhere in the world.
i. Upper and lower engine displacement limits will be established for each class, taking into account distinctions between 2-valve and multi-valve motors.
j. The class formula for weight/displacement is NOT intended to equalize the extremes of the class or make every bore/stroke combination competitive; rather, it offers all manufacturers and competitors the ability to build competitive engines by altering and/or exchanging existing blocks. The intention of the formula will be for optimum displacement/weight for the class to be near the center of the range.
k. Horsepower figures shown in the below table are planning guidelines only to be used to form an initial framework for the classes.
l. Engine bore and stroke will be free within established displacement limits.
m. Wheel sizes will be guided by the desires of the tire manufacturers in order to provide the greatest economic benefit to the competitor by maximizing tire competition.
2. Rotary Engine Definitions:
a. Street Port - as currently allowed in E Production
b. Bridge Port - as currently allowed in GT3
c. Peripheral Port - as currently allowed in GT2
3. Air Cooled Engines:
a. Should be factored at 102-105 hp per liter with 2-valve single plug head (exact hp figures to be reviewed).
4. Allowed Reciprocating Engine Mod:
a. Welding and re-machining combustion chamber, ports, valve perch, and overhead cam attachment area
b. No alteration of camshaft centerline or valve angle
c. Cylinder head origin must be OEM or SCCA approved factory homologated optional casting as listed in GTCS
d. Cylinder head choice and displacement will determine engine designation
e. Engine size and type declaration will be required on hood
5. Fuel Injection Guidelines:
a. Open (both method and manufacturer)
b. Independent runner
c. No balance pipes
d. Air inlet restriction (if necessary) by individual runner chokes or common inlet orifice. All engine air must pass through these measurable orifices
6. Engine Setback Rule:
a. Front axle spindle centerline 3" forward of leading spark plug (change is proposed to facilitate steering rack mounting due to clearance and geometry issues)
7. Suspension:
a. Solid axle is standard spec
b. Any car using IRS (by choice or by OEM design) may use it with a 100# weight penalty
c. OEM IRS designs defined as trailing arm, semi-trailing arm, or double A-arm
d. Will rework current front shock mounting location rule, deleting "outboard end" from the A-arm wording
8. Wheels and Tires:
a. GT4, 5 wheel and tire rules unchanged
b. Possible change to 18" wheels for GT1, 2 due to industry movement to larger diameter wheels and lower profile tires.
c. GT3 could be moved to 15x10 wheels for likely improvements in speed, durability, and consistency with only a small cost increase.
d. Suggestion has been made for GT3 to go to a maximum tire cross-section rule (for example 11"), rather than wheel width to allow either narrow wheels and cantilevered tires or wider wheels with straight sidewall tires. Could be expanded to other classes.
9. Brakes:
a. Dimensionally free in GT1,2,3 (restricted materials)
b. No change in GT4,5
10. Spoiler:
a. (Intent is to allow enough spoiler to be tuneabl
b.
c. Current spoiler cross-section wording stays as written. Air gap tolerance below spoiler of 1/8" to facilitate imperfect mounting will be included in overall spoiler height.
d. GT1 - 8" flat plane
e. GT2 - up to 6" flat plane
f. GT3 - up to 6" flat plane
g. GT4 - up to 5" flat plane
h. GT5 - up to 5" flat plane
11. Wheelbase Specifications:
a. Case by case request for homologation by manufacturer
b. Wheelbase will be as requested by the manufacturer
c. Current measurement tolerance remains
12. Bodywork:
a. Allow alternate windshield surround and roof materials on tube frame cars
b. Undertray/underbody - desire to merge GT rules with current Trans-Am rules in this area
c. Allow venting through rear license plate frame
d. Allow air ducts in rear quarter windows for differential and transmission coolers
e. Allow Trans-Am style "Taxi Window" option (polycarbonate bulkhea
f. in addition to metal bulkhead
g. No roadsters in GT classes. All current roadsters to have windshields by 1/1/02 and hardtops by 1/1/03
13. Grandfathering:
a. Current GT1,2,3 bodywork will be grandfathered for 5 years. After that, no bodywork will be allowed which has been out of US domestic delivery for more than 5 years.
b. No new GT4,5 cars will be registered for National racing after 1/01/02 with bodywork which has been out of US domestic delivery for more than 5 years. Cars registered by 1/01/02 may continue to compete if the vehicle logbook shows completion of at least one National race per year.
c. GT1 engines will also be grandfathered for 5 years. Eventual desire is to go to a 2-valve V-8 displacement limit of 5.1 liters to minimize weight variations in the class.
d. It is recognized that many GT1 competitors have a significant investment in 5.7 liter 9:1 compression engines. The weight required to keep these cars equalized is not fully consistent with the desire to limit the weight range for the class. This issue is under review.
e. Proposed bodywork grandfathering rule: No car registered or reinstated after 1/01/02 with a body style out of production world-wide more than 5 years. (Body must still must have been imported into the U.S.)
f. All current GT Category roadsters would have windshields by 1/1/02 and hardtops by 1/1/03

GT Category Key Specification Framework
GT1
Max HP More than 2-VDisplacement 2-V Displacement Rotary Notes
670 3.0 - 4.0 5.1 20B 3 rotor, peripheral port, restricted to 475 hp
Power to Weight ratio - 4.1 - 4.5 Weight: 2,000 - 2,750 lbs
F.I. - unrestricted, no variable runner Max Wheel Size: 18x12