TM-9-2815-220-24 Maintenance Manual for AVDS-1790-2CA AVDS-1790-DA and AVDS-1790-2DR Engines Download
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TM 9-2815-220-24 THEORY OF OPERATION 0004 00 ENGINE COMPONENTS (Continued) Cylinder and Head Assembly: Each cylinder assembly is an individually replaceable unit that consists of a barrel, cooling fin muff, and a cylinder head. The cylinder barrel, dome, intake and exhaust port liners are made of steel. The aluminum cylinder head cooling fins are cast to the steel dome. The cooling fins for the barrel are machined into an aluminum muff and shrunk onto the steel barrel. After the cylinder barrel fins are machined, the head and barrel are electron-beam welded to form a single unit. Valve guides and seats are shrunk into place in the head. The cylinder barrel is tapered at the head end to provide a straight bore under running conditions. A mounting flange is machined on the cylinder barrel near the base to provide an attachment of the cylinder to the crankcase. The cylinder assembly is secured to the crankcase with studs and nuts. An outer extension of the cylinder head provides mounting for the fuel injection nozzle and encloses a recess or rocker box, which houses the valves, valve springs, and related parts. Rocker arm assemblies are held in place by rocker shafts in the cylinder head valve rocker support cover. The stem of the intake valve and exhaust valve for each cylinder extends into the rocker box. Three nested springs, compressed between two retainers and secured to the valve stem by two cone-shaped locks, hold each valve to its seat. Each exhaust valve has a positive valve rotator, which also serves as the lower spring retainer. Valve clearance adjusting screws with flat swivel pusher pads are mounted on one end of the valve rocker arms. Forged steel valve rocker arms with roller cam- followers are used. The rollers are hardened and honed to provide an extremely smooth and permanent contact surface. Hollow rocker arm shafts and drilled passages in the rocker arms convey oil to all moving parts. A camshaft bearing surface is provided in each cylinder and is split equally between the cover and the cylinder head. The camshaft bearing surface is bored with the cylinder head valve rocker support cover in place. Therefore, the covers are not interchangeable and each must remain as part of a specific cylinder assembly. Identifying numbers are used on cylinders and covers to prevent mismatching. Each cylinder has replaceable camshaft bearings at the camshaft bore. Counter bores in the rocker box and rocker support covers accommodate inter- cylinder rubber hoses and steel flanges which enclose the camshaft between the cylinders. WP 0004 00-16