Place the pulley on the crankshaft nose without tightening the pulley mounting nut. Set the piston of the 1st cylinder to the TDC position at the end of the compression stroke. In this case, the TDC mark on the pulley should be opposite the pointer (models "518", "520") or tide (models "525", "528") on the lower timing cover. Make sure this is done when installing the timing cover.
Insert the chain into the guide and place it on the crankshaft sprocket in accordance with the timing mark applied to the chain when it was removed.
Connect both branches of the chain with wire at the top of the damper.
Install the lower timing cover gasket and apply Atmosit type sealing paste to the lower mating surface of the cover.
Remove the crankshaft pulley without turning the shaft, then install the lower timing cover.
After assembling the cylinder heads (see "Cylinder head assembly") install the camshaft flange so that the dowel pin points downwards. In this case, the mark on the flange (models "518", "520") must be aligned with the installation lug on the cylinder head (see photo in the subsection "Installing the cylinder head"). On models "525" and "528" the flange locating pin should be offset at an angle of approximately 45° downwards and to the left.
The upper threaded hole must align with the mounting boss on the cylinder head (see picture).
Place a dry gasket on the cylinder head studs (the installation of the gasket is possible only in one position). Install the cylinder head. Tighten the mounting bolts in three stages in the specified order (see above).
Disconnect the chain branches and place it on the camshaft sprocket, aligning the holes in the pulley and in the camshaft flange (models "518", "520").
Tighten the camshaft sprocket mounting bolts and lock them by bending the locking plates.
Pour engine oil into the recess of the upper timing cover to the level of the chain tensioner plunger. Bleed the chain tensioner as follows:
- install the plunger and tensioner spring; in this case it is necessary to insert the front groove of the plunger into the bracket of the tensioner shoe and direct the spring with the conical part towards the plug;
- partially tighten the tensioner plug;
- press the tensioner shoe bracket several times with a screwdriver until oil starts to flow out of the plug;
- wipe the cork and screw it on tightly.
Note: Causes of camshaft drive chain noise may include air in the plunger, plunger sticking, clogged plunger ventilation slots, faulty ball valve, excessively stiff or weak plunger spring, or sticking chain tensioner shoe bracket.
Install the upper timing mechanism drive cover, having previously applied a sealant such as Atmosit to its lower part.
Install the ignition distributor bracket. Set the ignition distributor in such a position that the rotor is opposite the mark on the distributor housing, and the piston of the 1st cylinder is at TDC of the end of the compression stroke.
Insert the segment keys into the sockets on the front end of the crankshaft, press in the new front crankshaft oil seal. Install the crankshaft pulley and secure it with a nut and washer, tightening it to a torque of 14.0-15.0 kgf·m.
Install the clutch, positioning the driven disk with the protruding part towards the pressure plate and center the disk relative to the flywheel with a mandrel.
Adjust the valve drive clearances. Install the removed components and assemblies onto the engine.
Stop the engine (or power unit) and install it on the car.
Since 1978 model year, engine disassembly and assembly "525", "528" and "528i" are produced taking into account the following:
- when replacing the camshaft drive chain: remove the distributor cap; set the piston of the 1st cylinder to the TDC position, aligning the "OT" mark on the torsional vibration damper with the mark on the lower cover of the valve timing mechanism drive; the speed limiter must be directed towards the mark on the ignition distributor housing;
- when replacing the crankshaft sprocket: remove the camshaft drive chain, oil pan, oil pump drive sprocket; remove the woodruff key and remove the oil seal from the crankshaft sprocket; press the sprocket with a puller 112000; replace the camshaft drive chain and the oil pump drive chain;
- when replacing the valve rocker shafts: after removing the threaded plugs, screw in the 113060 tool (previously 7004); remove the mounting studs, press out the front valve rocker arm axles; installation is carried out in the following order: spring 3 (see photo), washer 4, rocker 5, thrust ring 6;
- when replacing the valve rocker arms: install the calibrated screw 1 (see photo), eccentric 2, washer 3 and nut 4 on the new rocker arm. If the eccentric is worn, replace it.
Note: The calibrated screw and nut have a thread of M6x0.75. The flat of the calibrated screw should be directed towards the back of the rocker arm.