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Engine Oil Pump - Dry Sump Oiling
Engine lubrication is supplied by a two-stage oil pump assembly. The oil pump assembly consists of a primary vane-type
variable displacement pump and a secondary geroter-style pump. The primary pump contains a pressure relief valve that
protects the oil pan mounted oil filter from over pressurization during cold engine start up. If system pressure exceeds 600
kPa (87 psi), the pressure relief valve will open and exhaust oil back into the oil pan. The front or forward gear set is the
secondary pump. The rear or rearward housing contains the primary pump. The pump assembly is mounted at the front
of the engine and driven directly by the crankshaft sprocket. The vanes of the primary pump rotate clockwise and draw oil
from the engine oil tank through the oil tank screen. The oil is pressurized as it passes through the primary pump and is sent
through the engine block lower oil gallery.
Pressurized oil is directed through the engine block lower oil gallery to the full flow oil filter where harmful contaminants are
removed. A bypass valve is incorporated into the oil filter, which permits oil flow in the event the filter becomes restricted.
Oil exits the oil filter and is then directed to the external oil cooler. The external oil cooler is a liquid to liquid (engine coolant
to oil) oil cooler and consists of an oil pan mounted core and coolant lines that connect the oil cooler to the engine cooling
circuit. A bypass valve is incorporated into the oil cooler assembly in the event oil flow within the cooler is restricted. Oil
returns from the oil cooler and is directed to the upper engine main oil galleries.
The oil tank inlet port is used to supply scavenged oil from the engine to the storage tank. The oil tank outlet port is used
to supply non-aerated oil from the storage tank to the engine. Chevrolet Performance parts oil adaptor kit part number
25534412 can be used to convert to AN-12 fittings, when using specialized reservoir tank (Figure 3).
When replacing engine oil, there are two oil drain plugs within the oil pan. One plug drains the oil pan and the other plug
drains the storage tank. (Figure 3A).
Fig. 3
Oil tank outlet port
Fig. 3A
Engine Oil Cooling
The engine as delivered comes with a liquid to liquid engine oil cooler. Engine oil is pumped thru the cooler and engine
coolant is pumped thru the cooler, to transfer the engine oil heat into the engine coolant. The engine coolant should route to
the lower portion of the radiator, or inlet hose of the coolant pump. Heat is then removed by the engine radiator. Depending
on the installation, the engine oil cooler can be used or it can be removed. If using this heat exchanger, then the following
parts will assist in the installation (Figure 4).
LT4 Engine Installation
TITLE
Dry sump oil (LT4)
Oil tank inlet port
Oil system drain plugs
Front
19332703
IR 12AU15
PART NO.
6
40
SHEET
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