Steel crankshaft, with hardened journals, five-bearing, with lubrication channels and centrifugal traps for oil cleaning, main journal diameter 75-0.020mm, and connecting rod diameter 65.5-0.020mm (Fig. 1)

ZIL-131 crankshaft

Thin-walled trimetallic bearing shells 2.25-0.013 mm thick, interchangeable on each support (except the rear).

In the new engine, the diametrical clearance in the connection of the crankshaft main journal - the block with liners assembly is 0.026-0.085 mm.

The main bearing cap bolts must be tightened with a torque wrench. The tightening torque should be equal to 11-13 kgm.

Check and, if necessary, tighten the bolts of the main bearing caps every time the oil sump is removed.

In the new engine, the axial clearance of the crankshaft in the thrust bearings is 0.075-0.245 mm.

If the connecting rod or main bearings are worn, both halves of the bearings must be replaced at the same time.

The crankshaft is dynamically balanced with the flywheel and clutch.

The torque of the flywheel bolts on the crankshaft flange should be 14-15 kgm.

Design features of the crankshaft and flywheel (ZIL-131)

A rubber skeleton oil seal is installed at the front end of the crankshaft to prevent oil leakage.

For the same purpose, at the rear end of the crankshaft there is a drainage groove in the rear main bearing shell (with an oil drain hole), an oil-dumping ridge, an oil-removing spiral groove, an oil seal made of asbestos packing, an oil-removing spiral knurling on the crankshaft journal under the packing and rubber seals under the main bearing cap.

The cast-iron flywheel, with a steel ring gear for starting the engine from the starter, is attached to the flange of the rear end of the crankshaft with six bolts.

When removing the flywheel, to facilitate subsequent assembly, it should be noted that it is installed on the crankshaft, since the crankshaft flange has offset (asymmetrical) holes.

Tightening order for flywheel to crankshaft bolts (view of crankshaft flange).

When attaching the flywheel to the crankshaft flange, tighten the nuts evenly in the order shown in fig. 2.

It is necessary to monitor the accuracy of the cotter pins of the flywheel mounting bolts. The cotter pin should tightly fit the end of the bolt.

the installation of the flywheel, it is necessary to check the runout of its working surface (the mating surface with the clutch disc)

in relation to the axis of the crankshaft. At a radius of 150 mm, this runout should be no more than 0.15 mm.

Note: since October 1969, engines have been produced with bimetallic liners 2.5-0.025 mm thick and with a crankshaft having main journals with a diameter of 74.5-0.020 mm.

The diametrical clearance in the connection of the main journal - the block with liners as an assembly in the new engine is 0.050-0.107 mm. The crankshaft complete with liners is interchangeable.