Crankshaft, Flywheel, and Damper

1-15. Cylinders and Valves

1-12. Crankshaft, Flywheel, and Damper

Note. The key letters shown below in

parentheses refer to figure 1-8 except where

parentheses refer to figure 1-8.

otherwise indicated.

a. Crankshaft assembly (QQ) is a nitrided steel

a. Each cylinder assembly (fig. 1-1) is an

forging with seven main bearing journals and six

individually replaceable unit that consists of a

crankpins. Each crankpin accommodates two

barrel, cooling fin muff, and a cylinder head.

opposing connecting rod assemblies (UU ).

The cooling fin muff is cast directly on the steel

Flanges are provided on the crankshaft for

barrel. The finned, cast aluminum cylinder head

mounting the flywheel (N ) on the rear end and a

is threaded and shrunk on the barrel. Cooling

torsional vibration damper (TT ) on the front

fins, exhaust and intake ports, and a single

end.

rocker box are cast integrally with the cylinder

b. All crankpin and main bearing journals are

head. Valve guides and seats are shrunk into

hollow to reduce weight. Holes are drilled

place in the head, The cylinder barrel is

diagonally through each main bearing journal

"choked" at the head end to provide a straight

and extend through the crank cheek and crank-

bore under running conditions. A mounting

pin to provide a direct passage for oil under

flange is machined on the cylinder barrel near

pressure to the connecting rod and crankshaft

the base to provide an attachment of the cylinder

main bearings as shown in figure 1-9.

to the crankcase. The cylinder assembly is

c. The crankshaft and flywheel are statically

secured to the crankcase with studs and nuts. An

and dynamically balanced.

outer extension of the cylinder head encloses a

d. The torsional vibration damper (TT) is a

recess or rocker box, which houses the valves,

precision viscous type and is replaceable only as

valve springs, and related parts. Rocker arm

an assembly.

assemblies (A and B ) are held in place by rocker

1-13. Connecting Rods and Bearings

shafts in the cylinder head valve rocker support

The connecting rod assemblies (UU, fig. 1-8)

cover.

are tapered, I-beam section steel forgings. A

b. A camshaft bearing surface is provided in

bronze-lined, steel-backed, split, bushing type

each cylinder. The camshaft bearing is bored

bearing is pressed into the piston pin end of the

with the cylinder head valve rocker support

rod. The replaceable precision connecting rod

cover in place. Therefore the covers are not

bearings are the steel-backed, split type having

interchangeable and each must remain as a part

copper-lead alloy bearing surfaces.

of a specific cylinder assembly. Identifying

1-14. Pistons, Pins and Rings

numbers are used on cylinder and covers to

The pistons (VV, fig. 1-8) are aluminum

prevent mismatching. Counterbores in the

forgings, cam ground and tapered to provide an

rocker box. and rocker support covers ac-

accurate fit in the cylinders at operating tern.

commodate the intercylinder rubber hoses and

peratures. The piston dome is machined to the

the steel flanges which enclose the camshaft

shape of a conical section (toridal shape) so that

between the cylinders.

it tapers into the open type combustion chamber.

c. The stem of the intake valve (YY) and

Each piston is fitted with four rings. The upper

exhaust valve (XX ), for each cylinder, extends

three rings are compression rings and the bottom

into the rocker box. Three nested springs,

ring is an oil control ring. The heavy walled,

compressed between two retainers and secured to

tubular, steel piston pins are full-floating in the

the valve stem by two cone-shaped locks, hold

p i s t o n and the connecting rod. Domed

each valve to its seat. Each exhaust valve has a

aluminum plugs are inserted into each end of the

positive valve rotator which also serves as the

piston pin to center it in the piston and prevent

lower spring retainer. Valve clearance adjusting

scoring of the cylinder wall.

screws with flat swivel pusher pads are mounted

on one end of the valve rocker arms (A and B).

1-6