Big J at the Commercial Show, Earls Court.

The Big J (Big Jaguar) was the successor to the Warrior and Invincible range of trucks. It arrived in 1964 and featured an all steel cab manufactured by Coventry Motor Panels. The basic cab design was also sold by them to other truck manufacturers such as Seddon. Originally, the cab was designed to have the capability to be tilted for engine access, but in the final production version, this feature was not fully developed. The front cab mounting still remained as a hinge, but in practice, it was not possible to tilt the cab. The possibility for tilting came about because the truck was intended to have a new engine – the Cummins VIM V6. As part of a projected deal between Jaguar and Cummins, the Cummins VIM V.6 and VINE V.8 engines were slated to be made at the Henry Meadows factory, also owned by Jaguar, situated next door to Guy Motors factory in Park Lane, Wolverhampton. In the event, the engine proved to be problematical, and was not fitted to most trucks. Many other engines were offered, and these were mostly inline 6 cylinder types, which did not permit the same space for tilting.

Early Big J with cab tilted, Cummins V6 Engine. Note the air intake pipe fixed to the rear cab mounting tower. The holes for this were present in every mounting tower, even though this was the only engine variant to use them.

The image below shows a photograph taken at Guy Motors of an early BigJ4 tractor chassis. The engine is the Cummins V6. The early trucks had no power steering. The manual handbrake is fitted, albeit with air assistance – the air cylinder can be seen behind the fuel tank. Late models had spring brakes and so needed no handbrake lever. This photograph was used by an illustrator to draw a cutaway view of the chassis for the brochure.

Here is a cab view from the early Big J. The advantage of the Cummins V6 engine was that there was room in front of the engine cover to move across the cab. A “Walkthrough” cab, in effect. The later straight 6 cylinder engines, from Gardner, Cummins and Rolls Royce, intruded further into the cab and made this impossible.