The International Motor Sport Association ran its first full season in 1971. It was similar to the European GT Championship as there were no prototypes. It was an alternative to the SCCA Trans-Am, and was better managed. From the earliest years, Camel Cigaretttes were the title sponsor, and the term "IMSA Camel GT" was the de facto name that Americans like myself used for "sportscar endurance racing". Both IMSA and Camel's brand image flourished during this partnership.
An early Camel GT logo
This image coutresy of Andrew S. Hartwell, the creator of the first-rate sportscar photo site ASHautomobilia.
The main classes were GTO and GTU, which stood for "Grand Touring Over (2 litres)" and "Grand Touring Under".
For the first time in decades, Sebring was not a World Championship Event. Instead, a Porsche Carerra RSR running in the top-level "GTO" class took the win.
IMSA 1973 | |||||
Place |
Car |
Car # Class |
Model |
Ref. # |
Image |
| Sebring 12 Hours | |||||
| 1 | Porsche Carerra RSR 'Garrard' Hurley Haywood  Peter Gregg Dave Helmick | 59 GTO | Minichamps | 430 736999 |  |
While the BMW sport coupes have always been a strong presence, the cars have never seemed sporty enough to get excited about.
This exerpt is from the BMW CCA Website
In 1975, the CSL of Brian Redman, Allan Moffat, Hans Stuck, and Sam Posey led for most of the race, then survived a failing differential in the waning moments of the enduro to beat the Porsches to the checker.
This year the 1975-winning #25 CSL was on display in the Prototype Technology Group paddock along with the team's exciting new E46 M3, and Redman, Posey, and Stuck were on hand to talk about the old days. Redman, who drove seven of the twelve hours in 1975, said, "With about twenty minutes to go, we had a two-lap lead, and Ijust glanced at the gauges-a routine look as I came past the pits-and the oil temperature gauge for the rear axle was off the top. And tears came to my eyes. I thought, 'It's going to break,' and I slowed right down, went as slowly as I could. I probably went from running 120-130 miles an hour to running 50, and I watched pit signals as the gap came down. The second car was catching up like crazy, but we just won. A pinion bearing had failed in the axle. It could have gone at any time -- but it held out."
IMSA needed to get some American cars on the grid to add variety to the Porsche parade. There were no capable cars coming out of Detroit, so they created a new tubeframe class.
A normal road car is considered to be a unibody construction. This means that most of the frame is formed by pressed sheet metal. This makes a tub shape that provides the stiffness
A tubeframe car is made of metal "pipes" welded together at intersections with the body hanging on as an appendige
These retained most of the contours of the body panels, doors, and windshield. But ths really ruins some of the spirit of things, as they are no longer cars you can buy and drive.
This was the most successful of the tubeframe cars. But to me the term Chevy Monza equates to "rusting piece of crap". However, the DeKon-built Monzas were decent cars.
IMSA 1975 | |||||
Place |
Car |
Car # Class |
Model |
Ref. # |
Image |
| 1 | BMW CSL 3.0'BMW' Brian Redman  Allan Moffat  | 25 GTO | Minichamps | 430 752925 |  |
IMSA 1977 | |||||
Place |
Car |
Car # Class |
Model |
Ref. # |
Image |
| Daytona 24 Hours | |||||
| 10 | Porsche 934 'Brumos' Jim Busby Peter Gregg | 61 GTO | Universal Hobbies ('Eagle Collectibles') | UNHV2305 |  |
| 40 | BMW 320i 'First National City' David Hobbs Ronnie Peterson  Sam Posey | 2 GTO | Quartzo ('3000 Series') | 3037 |  |
| 53 | Porsche GTP 'Interscope' Danny Ongais George Follmer Ted Field | 00 Sports | Ebbro | 44019 |  |
International Motor Sports Association 1978 | |||||
Place |
Car |
Car # Class |
Model |
Ref. # |
Image |
53 | Ferrari 308 GTB | 8 | Vitesse | L112 |  |
The 1979 Daytona 24 hour race was technically part of the World Sportscar Championship, but it was sanctioned by and run to IMSA's specifications. Therefore the models from this race appear in this section only.
These GTU Mazdas were the backbone of IMSA for years, and the GTU designation was used for the "sporty" version of the production model. The IMSA GTU classes ran separate races at shorter events.
An unsung hero of this era is Jim Downing, whose independent spirit developed the Kudzu cars. He ran the Mazda rotary engines, which made him get his own section in the rulebook. He also developed the HANS safety device that may revolutionize crash safety. The device prevents Dale-Earnhardt-like whiplash, and by most accounts does not impair the driver's sight or movement.
International Motor Sports Association 1979 | |||||
Place |
Car |
Car # Class |
Model |
Ref. # |
Image |
| Daytona 24 Hours (Part of the World Championship and IMSA) | |||||
5 | Mazda RX-7 | 7 | Ebbro | 43238 |  |
6 | Mazda RX-7 | 77 | Ebbro | 43239 |  |
| 53 | Ferrari 512 BB Jean-Claude Andruet  Spartaco Dini  Claude Ballot-Léna | 66 GTX | Brumm | 411 |  |
