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 TM 55-1905-220-14-6
3-164. CYLINDER HEAD - MAINTENANCE INSTRUCTIONS.
a.
General
(1) The cylinder head, one on each cylinder bank, is a one-piece casting securely held to the cylinder block
by special bolts. The exhaust valves, fuel injectors and the valve and injector operating mechanisms are
located in the cylinder head.
(2) Four exhaust valves are provided for each cylinder. Exhaust valve seat inserts, pressed into the
cylinder head, permit accurate seating of valves under varying conditions of temperature and prolong the life of
the cylinder head.
(3) To ensure efficient cooling, each fuel injector is inserted into a thin-walled tube, which passes thru the
water space in the cylinder head. The lower end of the injector tube is pressed into
the cylinder head and flared over; the upper end is flanged and sealed with neoprene seal. The sealed upper
end and flared lower end of the injector tube prevent water and compression leaks.
(4) The exhaust passages from the exhaust valves of each cylinder lead through a single port to the
exhaust manifold. The exhaust passages and the injector tubes are surrounded by engine coolant. Cooling is
further ensured by the use of water nozzles pressed into the water inlet ports in the cylinder head. The noz-
zles direct the comparatively cool engine coolant at high velocity toward the sections of the cylinder head which
are subjected to the greatest heat.
(5) The fuel inlet and outlet manifolds are cast as an integral part of the cylinder heads. Tapped holes are
provided for connection of the fuel lines at various points along each manifold.
(6) To seal compressions between the cylinder head and the cylinder liner, separate laminated metal
gaskets are provided at each cylinder. Water and oil passages between the cylinder head and
cylinder block are sealed with synthetic rubber seal rings which fit into counter-bored holes in the block. A
synthetic rubber seal fits into a milled groove near the perimeter of the block. When the cylinder head is drawn
down, a positive leak-proof, metal-to-metal contact is assured between the head and the block.
b.
Cylinder Head Maintenance
(1) The engine operating temperature should be maintained between 160 to 185F (71C to 85C), and the
cooling system should be inspected daily and kept full at all times. The cylinder head fire deck will overheat and
crack in a short time if the coolant does not cover the fire deck surface. When necessary, add water very
slowly to a hot engine to avoid rapid cooling which can result in cracking and distortion of the cylinder head and
block.
3-2686
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