CAT Engines Course ( Part 1)

INTRODUCTION
This presentation is about the 3500 Series Engine. One arrangement of the 3516 Vehicular Engine is used for most illustrations.

The 3500 Series Engine is a diesel engine with a
4-stroke cycle. It has a 60 degree “Vee” angle between the cylinders of the block. The cylinder bore is 170 mm (6.7 inch) and the piston stroke is 190 mm (7.5 inch). Each cylinder has approximately 4310 cu. cm. (263 cu. in.).

Standard engine rotation is counterclockwise. See
the Service Manual for Firing under specs (V8
and V16).

ORIENTATION
Looking at the right side of the engine, we see the:
1. cylinder heads, block and oil pan
2. valve covers
3. rear lifting eye
4. turbocharger (one of two)
5. oil cooler and oil pump
6. fuel priming pump, two secondary fuel filters,
and fuel transfer pump
7. crankcase filler opening and dipstick
8. air starting motor
9. water pump; and
10. alternator

NOTE: This is the first Caterpillar engine designed to
metric dimensions. All engines in the series have the
same bore and stroke and have the push rod valve
design. All engines are turbo charged and
aftercooled. All 3500 Series Engines have direct
injection combustion systems with a unit injector
fuel system.


On the front of the engine, we see:
1. the Caterpillar 3161 governor
2. the water pump and the line to the aftercooler
3. the thermostat housing and the bypass line
4. the vibration damper, and crankshaft pulley
The fan pulley and idler pulley is driven from the
crankshaft pulley belts. The fan pulley and idler
pulley each have an adjustment to adjust the
tension of the fan (drive) belts.
The plates shown on the right can be removed to install
other accessories on the auxiliary drives. The
governor and crankcase breather can be installed
on either the left side or right side.

On the left side we see:
1. the oil supply line (arrow)
2. the oil filter base/housing and four oil filters
3. the oil supply and oil drain for the turbocharger
4. the fume disposal group
Also on the rear we see three auxiliary drives above the
flywheel housing. Two turbochargers are
installed on this engine. This is the location of
the turbochargers on the vehicle arrangements.
Turbochargers can also be installed above the
rear of the engine for industrial generator set and
marine engines (shown later)

BASIC ENGINE
This is the flywheel housing and the flywheel. The
standard vehicular flywheel housing is SAE No.
“O”. The flywheel housing for the Marine,
Industrial, and Generator Set is SAE “OO”. The
SAE No. “O” is available for Marine, Industrial,
and Generator Set engines.

The starting motor is normally installed on the right
side of the engine. An air starting motor is
shown. There are two optional locations for the
starting motors.

. . . on the left side. The two plates cover the openings
for the optional locations for the starting motors.
Air or electric starting motors are also available.

SERIAL NUMBER PLATE
The serial number plate is on the left side of the
camshaft compartment near the rear of the
engine block.
Also you can see the location of the camshaft
compartment covers and the crankcase
compartment covers.

The serial number plate has the model number, serial
number, arrangement number, and modification
number. All numbers must be included on
Service Reports with warranty claims and when
ordering parts.

INFORMATION PLATE
This information plate is on the right side of the engine.

On later engines, the plate is on the left-hand side in
front of the cylinder head. This plate has the
high idle rpm, full load rpm, power setting and
other important engine information.
Other plates and transfers (not shown) give you
information about valve adjustment.

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CAT Engine Course (Part 8) Valve Lash

ENGINE TURNING TOOL
The top bolt in the cover plate of the bore for the engine turning tool is the timing bolt. The timing bolt is used to find the location of No. 1 piston on top center (TC).
This is important to the serviceman because thereference point for all timing proce dures is with No. 1 piston put at top center on the compression stroke.
The pipe plug (arrow) is removed from the flywheel housing to install the timing bolt.

The optional engine turning tool fits in the bore in the flywheel housing and has teeth which engage with the flywheel gear teeth. The engine turning tool is a special tool used for rotation of the crankshaft of the engine when you need to make adjustments, time the engine, or turn an engine in storage.

A 1/2 inch drive ratchet is used to turn the tool and the engine crankshaft.

LOCATING TOP CENTER COMPRESSION STROKE FOR NO. 1 PISTONTo find top center compression stroke for No. 1 piston, first turn the flywheel clockwise a minimum of 30 degrees. The reason for making this step is to be sure the backlash is removed from the timing gears when the engine is put on top dead center.

Next, turn the flywheel counterclockwise until the hole in the flywheel is in alignment with the timing bolt. When the timing bolt can be turned freely in the threaded hole in the flywheel, the engine No. 1 piston is on top center.

To check to see if No. 1 piston is on compression stroke, look at the valves of No. 1 cylinder. The valves will be CLOSED if No. 1 cylinder is on compression stroke. You should be able to move the valve rocker arms up and down with your hand.
If No. 1 piston is NOT on compression stroke, turn the crankshaft 360 degrees and follow the procedure again to put No. 1 piston on top center.

VALVE AND BRIDGE ADJUSTMENT
With the valve cover removed, we can see the three rocker arm assemblies. The rocker arm on the left (1) activates the bridge and the two exhaust valves. The center rocker arm (2) activates the unit injector for fuel injection. The rocker arm on the right (3) activates the bridge and the two inlet (intake) valves.

NOTE: On production engines, lower thread bosses are removed. EXHAUST and INTAKE are stamped on housing.

The valve arrangement is the same as other engine valvesactivated by push rods, except a valve bridge. The bridge activates the two inlet valves or exhaust valves at the same time (similar to the 3400 Series Engines). The bridge fits on a dowel which is the guide when the bridge moves up and down. The bridge is moved (activated) by the rocker arm. Adjustment of the valve bridge is done when the engine is assembled and when valve lash adjustment is made.

To adjust the bridge, loosen the locknut, push down on the rocker arm (or point of contact) and turn the adjustment screw clockwise until it contacts the stem of the valve. Turn the adjustment screw an additional 20 to 30 degrees (1/3 to 1/2 of one side of the nut) to position the guide of the bridge straight on the dowel.
Tighten the locknut to specifications.

NOTE: Normally, adjustment of the bridge will be donewith the rocker arm assembly off the cylinder head.

VALVE CLEARANCE SETTINGValve clearance or valve lash is measured with a feeler gauge or 8T5207 setting gage, put between the rocker arm contact and the bridge wear seat. Valve clearance is changed using a screwdriver.

A 3/4 inch wrench is needed to loosen and tighten the locknut which holds the adjustment screw. To make the adjustment, turn the adjustment screw until you feel an easy pull on the feeler gauge as you move it backward and forward between the rocker arm contact and the bridge wear seat. Tighten the nut on the adjustment screw and check the adjustment to be sure it has not changed. The adjustment of all valves and the injectors can be done by putting the engine crankshaft in two positions. Refer to the Service Manual for these procedures.

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