Under the hood of the XK8

Automotive Manufacturing & Production, July, 1997

Of course, a car is more than sheet metal, so the XK8 is fitted with an all-new, Jaguar-designed, 290-hp V8 engine, which is being produced in a dedicated facility within the larger Ford engine plant in Brigdend, South Wales. The engines - referred to as the AJ-V8 by Jaguar personnel - are shipped to the car maker's Browns Lane plant in Coventry, England, for installation into the XK8s.

The engine is an all-aluminum, double-overhead cam, four-valve-per-cylinder unit with a 4.0-liter displacement. It provides 290 hp at 6,100 rpm and 284 ft.-lb. of torque at 4,200 rpm. The diecast aluminum block features a structural bedplate; this aluminum casting, which forms the bottom of the block, incorporates the five main-being caps in a single ladder-type structure, a design that helps result in both durability and reduced vibration.

Unlike many other aluminum engines, the AJ-V8 doesn't utilize cast iron cylinder liners. Instead, a nickel/silicon carbide finish is electroplated onto the surface of the cylinders. The electroplating process is called "Nikasil." Plating solutions are pumped through the block that's in an immersion tank. The process is controlled so that just a 0.003-in. thick coating covers the surfaces of the cylinders. Not only does this help reduce the weight of the engine - 15 additional pounds would be needed if the cast iron liners were used - but performance improvements are said to result, such as reduced friction (better fuel economy), faster warm ups (not only helps with fuel economy, but also with emissions), and improved oil retention.

Other materials used in the engine:

* Spheroidal graphite (SG) iron. This is used for the crankshaft and the camshafts. It is said to combine light weight with strength and durability. The cam-shafts are rifle-drilled along their main axis in order to help reduce even more weight.

* Steel - that's processed through sinterforging. The application: the connecting rods. The process permits the production of a single-piece con rod with high dimensional accuracy.

* Polyamide, a composite material. The molded air intake system is made with it. The material has insulation properties that help ensure quick starting when the engine is hot.

According to one of the suppliers of manufacturing equipment for the AJ-V8, John Nicklin, technical director of Marwin Production Systems (Wolverhampton, England), the machining specs for the engine are more accurate than is the norm. For example, the pilot bearing hole in the flywheel end of the crankshaft must be rough and finish bored to a total accuracy of 16 microns. Marwin supplied the crankshaft and camshaft end-machining lines to the Bridgend facility, so it knows about this one in some detail: "In practice," Nicklin said, "we have to achieve half the drawing tolerance, and the only way this is possible in a mass production environment is to in-process gage the hole and continuously apply automatic tool compensation. On all our previous similar projects, this was unnecessary."

(Marwin Production Systems, incidentally, is the international partner of Dayton Machine Tool Co. [Dayton, OH], a manufacturer of custom-built machines.)