Sir William Lyons and his brainiac engineers started conceiving the all-new XK engine amid fire-watching duties during WWII. The company had a running four-cylinder prototype after the war, and it had the base ingredients of what would eventually evolve into the Jaguar XK engine: Dual overhead camshafts, two valves per cylinder, hemispherical combustion chambers, and polished cam covers.
Moreover, the XK inline-six has two sets of three cylinders with wider spacing in the middle to improve the coolant flow. Each cylinder has a cast aluminum piston with dual compression rings, a single oil ring, and a full-floating wrist-pin design to minimize friction. Each piston has a dome on top to deliver an 8.0:1 compression ratio in early models of the XK 120.
Sealing the deal are shiny aluminum components like a cast aluminum head, front timing cover, cam covers, and oil pan. The decision to use an aluminum head saved 70 pounds, but the XK’s cast-iron engine block and transmission casing meant the entire powertrain tipped the scales at about 700 pounds.
