Production of the E-Type began with the Series 1 beginning in 1961 featuring the 3.8 liter six-cylinder engine from the XK-150. All E-Types were given an independent coil spring rear suspension with torsion bar front ends, and four-wheel, power assisted disc brakes. Notably, Jaguar was one of the first vehicle manufacturers to equip cars with disc brakes as standard equipment dating back to the XK-150 in 1958.
The competition continued to grow, with the lightweight Shelby Cobra and the big block Corvettes. Jaguar addressed the need for more power by adding another 6 cylinders, introducing the 5.3 liter 60-degree V12 E-Type in 1971, also known as the Series III.
Through the 1970s and 1980s, the racing scene in the United States continued to remain a hotly contested battlefield. There were two sanctioning bodies in the USA that were both promoting professional racing series; IMSA had the GT Categoreis and SCCA had the TransAm class. Manufactures from all over the world were participating in one or both of these series.
Long-time British car racer Bob Tullius, an American, got the contract to field this XJR-4 under the banner of his race team GROUP 44. Bob was well known for not only his skill as a driver but also his professionalism with regards to operating a race team. What Tullius came up with was the first tube framed Jaguar ever produced. He fitted it with the 6.0 Liter V-12 manufactured by Jaguar but highly modified by Group 44.
The car met the rules for both SCCA and IMSA so the car did double duty throughout its life and had great success, including three wins in the SCCA TransAm Series. The car was also used as a test bed to establish the endurance limits of the V-12 engine as Jaguar was considering plans to produce a Prototype race car for LeMans which would utilize this engine.