Page 14 - Demo

Page 14.Alvis Three Litre Shop Manual - T.A. 21 and T.C. 21THE ENGINEThe Three LLititre EEngi gineIs a six cylinder overhead valve engine of nearly square bore-stroke ratio. It has been designed to develop its most useful power output at medium rather than at peak engine speeds, resulting in a car possessing an exceedingly flexible top gear performance and outstanding powers of acceleration. The comparatively low piston speeds obtained by using a short stroke enable high cruising speeds to be effortlessly maintained.The crankshaft runs in seven white metal thin wall shell bearings located in the generously ribbed crankcase. Bearings of the same type are employed in the connecting rods, in the little ends of which the gudgeon pins are clamped, leaving the pins free to float in the pistons. Each piston has two compression and one scraper ring, the top compression ring being chromium plated in the interest of low cylinder bore wear. The valves are disposed in line in the lozenge shaped combustion chambers, and are actuated through rockers and push rods by light barrel tappets. The camshaft mounted high up in the cylinder block is carried in five white metal shell bearings. An automatically tensioned duplex roller chain drives the camshaft, a skew gear and vertical shaft take the drive from the camshaft to the distributor at the upper end and the submerged gear type oil pump in the crankcase sump.Twin S.U. Carburettors deliver mixture through a light alloy induction manifold each feeding three cylinders. The induction system for the front cylinders is, therefore, completely independent of that for the rear three cylinders. The same applies to the exhaust manifold which is also divided internally, the exhaust gases from each half being carried to the rear of the car through entirely separate silencers and exhaust pipes. The induction and exhaust manifolds are bolted together below the carburettor to form a localised hot-spot.