b. Engine-Compressor.
(1) The basic engine-compressor is a four-piston engine and a four-piston compressor. All eight pistons are
connected to a single crankshaft in the V-type crankcase. Power from the engine bank is transmitted
through the crankshaft to compress air in the compressor bank.
(2) The crankshaft is-mounted in five main bearings. Drilled holes from each main bearing journal to the
adjacent half of the crankpins permit oil to pass from the main bearings to the connecting rod bearings.
(3) Full pressure lubrication is supplied by a gear type pump mounted on the front main bearing cap. The
accessory drive, rocker arms, and all main bearings are lubricated and no other lubrication needs to be
supplied to the internal parts of the engine or compressor banks. The lubricating oil supply is filled through
the combination oil-fillercap and crankcase breather located in the engine bank saluter head cover. Two
bypass filters in the oil pan keep the lubricating oil clean.
(4) The ignition and electric starting system has been radio suppressed to prevent noise disturbances which
would interfere with proper reception of radio signals or which would permit detection of the compressor
location by receivers.
(5) The engine bank has four wet-sleeve type cylinders of 499 cubic inch displacement with a valve-in-head
designed for maximum fuel economy and low operating costs. Both exhaust and intake valves are stellite-
faced and each have stellite-faced inserts with positive-type valve rotators to increase valve life.
(6) The compressor bank also has four wet-sleeve type cylinders. Above each cylinder, in the compressor
cylinder head, is a compressor valve assembly. Free air is admitted through the dry-type air cleaners and
the intake valve part of the assembly by the action of the piston on its downward stroke. As the piston
moves up from bottom dead center the suction valve is closed. When the pressure in the' cylinder rises
slightly above that in the discharge manifold, the discharge valve port will open allowing air in the cylinder to
flow into the compressor discharge manifold. The valve assembly is connected to an automatic operating
pressure control system.
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