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Engine run-in after overhaul
After overhaul the engine is bench tested (run-in) at no loads
under the following cycle:
750-800 rpm
1000 rpm
1500 rpm
2000 rpm
Locate the engine on the test bench, start the engine and
make checks with respect to the following items:
- evidence of coolant or fuel leaks through mating compo-
nents, pipe connections or gaskets;
- oil pressure and oil leaks through gaskets;
- ignition timing;
- idle speed;
- carburettor / intake pipe tightness;
- abnormal knock.
In case of any malfunctions or unknown rattle, stop the
engine, eliminate the faults, then continue the tests.
In case of oil leaks through the gasket between the valve
cover and cylinder head or through the gaskets between the oil
sump, cylinder block and covers, tighten the securing bolts to the
torque specified. If oil leaks persist, check the correct fitting of the
gaskets and renew when applicable.
Since the overhauled engine is not fully bed-in and frictions
between the working surfaces of renewed parts show significant
resistance to the rotation, a certain run-in period is required.
This especially concerns those engines, where the pistons,
main / big-end bearing shells have been renewed, or the crank-
shaft journals have been reground, or the cylinders - honed.
Therefore during run-in after the engine overhaul, never allow
the engine to run at maximum loads. When in the vehicle, always
run-in the engine at the speeds which are recommended for the
run-in periods.
In-vehicle engine inspection after overhaul
Locate the engine in the vehicle, thoroughly check its correct
mounting.
Run the engine for a while, then check for:
- coolant or fuel leaks through pipe connections, tighten when
necessary;
- full throttle opening and closing by the carburettor cable,
adjust accordingly, if necessary;
- alternator drivebelt tension, adjust, when applicable;
- reliable wiring connections and operation of the warning
lamps in the instrument cluster.
2 minutes
3 minutes
4 minutes
5 minutes
WARNING. Never check the engine or vehicle on the
roller stand without additional rollers for the front wheels.
Cylinder block
General description
The cylinder block basic sizes are shown in Fig.2-25.
The cylinder block is of a low-alloyed cast iron. The cylinder
bores are of five classes in steps of 0.01 mm and are designated
by the letters A, B, ë, D, Ö. The cylinder class is engraved on the
cylinder block bottom face. (Fig.2-26).
The cylinders can be rebored to accommodate the oversize
pistons of 0.4 mm and 0.8 mm bigger diameters.
The main bearing caps are machined complete with the cylin-
der block; therefore they are not interchangeable and feature dis-
tinctive notches on the outside surface (Fig.2-13).
Inspection and repair
Inspection. Wash the cylinder block thoroughly and clear the oil-
ways. Blow dry with compressed air and inspect the cylinder
block visually. Make sure there are no cracks in the mountings or
elsewhere in the cylinder block.
When cooling water is suspected in the crankcase, use a
special test bench to examine the cylinder block for leaks. To do
this, plug the cylinder block cooling water jacket ports, force in
some room temperature water at 0.3 MPa (3 kgf/sq.cm). There
should be no evidence of water leaks from the cylinder block with-
in 2 minutes.
When coolant is found contaminated with oil, do not strip the
engine completely, rather check the cylinder block for cracks in
the area of the oilways. For that, drain the coolant from the cool-
ing system, remove the cylinder head, refill the cylinder block
water jacket with water and apply compressed air to the vertical
oilway in the cylinder. If there are any bubbles in the water of the
cooling water jacket, renew the cylinder block.
Examine the split face between the cylinder block and cylin-
der head using a straight-edge and feeler blades. Position the
straight-edge diagonally and using a feeler gauge measure at the
centre, both transversely and longitudinally. The flatness to be
within 0.1 mm tolerance.
Cylinder repair. Check the cylinders for wear to be maximum
0.15 mm.
When available, use a dial inside gauge to measure the bore
diameter (Fig.2-27) in four lands, both longitudinally and trans-
versely (Fig.2-28). Use tool 67.8125.9502 to set the inside gauge
to zero.
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