Engines

British rear-engined double-deck buses from 1958 onwards have had the engine mounted transversely at the extreme of the rear overhang, with the exception of the Bristol VRL (1968-1972). The engine is on the left (nearside), with the gearbox attached on the right (offside). If a turbocharger is fitted, it usually goes above the gearbox. (However, the Dennis Trident of the late 1990s onward has its shorter, more compact engine on the right.)

767 being overhauled at Longstone to become a trainer

Views of the engine compartment of 763 show the TL11 engine with gearbox and turbocharger. Some Olympians of the mid 1980s have the louvres on the left side like 763, but later Olympians usually have this panel plain.

The Leyland TL11 (11.1 litres) was developed in the later 1970s from the 680 engine (11.1 litres) of the mid 1950s, which itself was an enlarged version of the 600 engine (9.8 litres) of the late 1940s. Thousands of trucks and buses, Leylands, Daimlers, Guys, Bristols, Scammells, in the UK and abroad, had 600, 680 or TL11 engines.		The 600 could be set to deliver between 125 and 140 bhp, the 680 between 150 and 202 bhp, and the TL11 between 170 and 260 bhp.
The slow-revving 600, 680 and TL11 engines all had a distinctive, bell-like, heavy, ringing sound produced by each knock of the cylinders. To a lesser extent the smaller Leyland engines, 350, 370, 375, 400/410 and 500/510, had this as well. It is quite different from the more business-like sound of the equally slow-revving Gardner engines. It is very different from the harsh, fast, whirring noise of modern Cummins and Volvo engines, which sound like an oversize version of a Ford Sierra I once had. AEC engines in trucks and buses had a sound with some of the ringing quality of Leylands. AEC engines of course are only heard now on preserved vehicles. The Dutch company DAF's 11.6 litre engine makes a sound a bit like a Leyland 680; not surprisingly, since in the 1960s DAF used to supply their vehicles with Leyland engines, and based their own principal truck and bus engine on the 680 design.		Gardner, after a seventy-year history of developing first-rate diesel engines, no longer make complete engines, only parts. As with Leyland engines, most Gardner products could not meet modern noise regulations. Somehow, the terrible racket from a 2002 Dennis Trident, with the fan roaring on the nearside and the transmission whining, moaning and wailing, supposedly meets the regulations! You have to wonder which components of noise are being measured.