Welcome to the IMSA History unofficial website

This site is aimed at bringing you memories from the glory days of sportscar racing in the US.



Howard Katz entered this Chevrolet powered Tiga GT286 in 1987.

The Lights class was the home for smaller prototypes with a maximum of 3,4L displacement. Many manufacturers would build such cars, which were less expensive than GTPs. Spice Fieros, Argo JM16s and JM19s, Tiga GT285s, TIGA GT286s and TIGA GT287s, Denali Mazda, Royale RP40s were familiar Lights entrants.

In 1985, IMSA has developed rules for cars known as GTP(Grand Touring Prototype) Lights cars.

GTP were two-seaters conceived primarily for competition in closed circuit races. They carried equipment for normal road use and all safety devices. They did need not meet production requirements nor be offered to the public. Car identification was by engine manufacturer first, then the manufacturer of the chassis.

The eligible engines were :
  • Type 1 : 2-valve conventional engine with a maximum of 3,4L displacement
  • Type 2 : 4-valve conventional production engine up to 3,0L and 6 cylinders
  • Type 3 and 4 : not eligible
  • Type 5 : rotary engines Two rotor (12A, 13B) or Three rotor (13G,20B)
Engine modifications were free, except as follows :
  • Type 2 production engines and all Type 1 engines must use the production block or an IMSA approved alternate block.
  • Type 1 engines may use modified or alternate cylinder heads that retain the original number and location of valves, camshafts and spark plugs.
  • Type 2 production engines must use the production cylinder heads that retain the original number and location of valves, camshafts and spark plugs. The heads may be modified but material may not be added.
  • Oil tank was limited to 20 liters capacity.
Chassis :

Wheelbase was free

Overall length : 480cm

Overall width : 200cm

Overall height : min : 100cm max : 110cm

Two seats of similar construction and of equal dimension must be mounted in the cockpit

Air intakes may protrude from the plane of the bodywork provided they did not impair the driver's field of vision.


All coachwork had to be mounted to the fully sprung part of the chassis.

The coachwork sections had to be contiguous and cover all mechanical components when viewed from above.

Wheels and Tires:

Wheel and tire section width may not exceed 16".

All four rims should be of the same diameter.

Aerodynamic devices:

Aerodynamic devices were governed by the rules of overall length, width and overhangs of an individual automobile.

Cars are permitted a single element wing to which may be added separate flaps, with no more than one inch of air passing between them.