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Kenper Miller and David Cowart dominated the 1981 GTO season with this BMW M1.


The GTO were big bore production based cars. It was the home of the big bangers, such as Chevrolet Corvettes and Camaros, Ford Mustangs and Ferrari 365GTB4, then later BMW M1s, Datsun 280ZX Tcs.
Engines:

Proprietary engine block could be used; may be machined so long as camshaft location was not altered.

Bore and stroke could be altered so long as the appropriate weight regulation was respected.

Cylinder head could have same number and location of valves, ports and spark plugs.

Induction was free, except turbocharging was only permitted on FIA recognized models and was limited to one turbocharger.

Turbocharged engine displacement was 1.4 X actual displacement. Rotary engine displacement was 1.8 X actual displacement.

Engine could be relocated within the standard engine compartment.

Drive Train:

Gearbox or transaxle were free but must remain in standard location.

Maximum 5 forward speeds.

Rear axle had to remain live or independent as appropriate.

Chassis:

The standard body tub had to be retained along with standard wheelbase. Tube frame extensions were permitted.

All suspension components could be modified or replaced so long as wheelbase remained standard.

Brakes and operating system were free but components had to remain in the standard location.

Axle locating devices could not pass into the driver compartment; however, the rear seat well could be covered with sheet metal to satisfy this requirement.

Coachwork:

The original external shape and material had to be maintained except that the floor pan may be replaced by a continuous flat .032" steel or .040" alloy sheet. The firewall could be replaced with a similar metal sheet in the standard location.

Material of engine and luggage compartment covers, doors and fenders was free. Fender extensions were allowed to cover the legal wheels and tires but should retain the standard opening shape as viewed from the side. Any additional bodywork must not confuse the make and model identity of the car.

Bumpers and external decorative trim could be removed. Any substitute bumpers had to have standard dimensions and shapes.

Wheels and Tires:

Wheel and tire section width (maximum width at widest point of tire) could not exceed:

5.0L - 14", 6.0L - 15", over 6.0L - 16"

All four wheels must have the same diameter.

Track dimension was limited by inner tire clearance and the permitted maximum car width.

Aerodynamic devices:

An optional rear spoiler may be fitted to the rearmost part of the body without protruding beyond the perimeter contour as viewed from above.

Maximum height 6" above the standard bodywork. May not be adjustable from within car. No air may pass between spoiler and body.

Any front device had to be located below the centerline of the hubs and within the perimeter of the body when viewed from above.