July 11th and 12th, 1970 saw the World Sportscar Championship return for the third race of the year in the United States. Watkins Glen would host the Six Hour endurance race on Saturday and the Can-Am race on Sunday making it a double-header for some of the teams and drivers.
Porsche came into the weekend on a roll, having already clinched the Manufacturer’s Championship and having recorded their first overall victory at Le Mans. Ferrari had a poor race at Le Mans and hadn’t been close to a victory since Monza in late April. John Wyer’s JWAE/Gulf-Porsche team had a truly disastrous race at Le Mans and were looking to regain the dominant form they had shown most of the season.
Early on in practice, Jo Siffert was very unhappy with his Gulf 917 according to Ermanno Cuoghi in his book, Racing Mechanic: “Siffert was not happy with his car, it was just no good compared to Pedro’s. So we put Pedro’s car in one flat concrete bay and take all the suspension geometry readings off that car. Then we push Siffert’s car on the same spot, check everything out – especially bump and rebound settings- and it was quite a long way out. So we put Siffert’s car in exactly the same trim and Siffert was very happy with that car.” In Ian Wagstaff’s book, Porsche 917 – Owner’s Workshop Manual, mechanic Alan Hearn confirmed that bump steer (and toe-in) was critical on the 917 and something the JWAE mechanics worked on very carefully when setting up the cars in the workshop at Slough. At Watkins Glen, the team experimented with a revised rear fender shape to better accommodate 17-inch rear wheels. They also used special 10.5-inch front wheels to work better with revisions to the front suspension with reduced off-set. Although the track surface was new, it was breaking up in places so the team chose Firestone intermediate tires.