If the power unit is removed, disconnect the gearbox from the engine.
Disconnect the spark plug wires. On BMW "525" and "528" remove the wire mounting tube on the cylinder head cover and the distributor assembly.
Remove the distributor bracket mounted on the end of the camshaft.
Remove the carburetor and intake manifold.
On the model "520i" (with an engine with a fuel injection system "KugeHischer") disconnect the fuel supply lines to the injectors from the injection pump, disconnect the fuel line from the starting injector and the starting system power supply wire.
Remove the protective cover and exhaust manifold, generator, starter, cylinder head cover, fuel pump and its pusher.
Remove the camshaft chain tensioner spring and plunger while holding the spring in place.
Remove the upper timing drive cover, unscrew the camshaft sprocket mounting bolts, removing the locking plates.
Move the sprocket and chain forward away from the engine.
Loosen and remove the cylinder head mounting bolts in the reverse order of tightening.
Remove the cylinder head and gasket.
Remove the water pump assembly.
Remove the flywheel ring gear protective cover and lock the flywheel from turning using lock 6069.
Loosen the crankshaft pulley mounting nut and remove the pulley.
Remove the lower timing gear cover by unscrewing the bolts securing it to the block and oil pan. At the same time, push the cover forward to remove it from the mounting pins on the cylinder block.
Remove the camshaft sprocket and timing chain, making a paintable timing mark on the front side. Remove the chain guide and chain tensioner shoe.
Unscrew the bolts securing the flywheel mount housing and remove it together with the pressure plate. This releases the driven clutch disk. Note its position: the protruding part of the hub is directed toward the pressure plate.
Loosen the flywheel mounting bolts, remove retainer 6069, and remove the flywheel.
Remove the crankshaft rear oil seal holder, then press out the oil seal.
Drain the oil from the engine, turn the engine upside down and remove the oil pan.
Remove the oil pump (see above).
Check the markings on the connecting rod caps and main bearings (the covers are counted from the camshaft drive side) and, if necessary, mark them.
Loosen the connecting rod bolt nuts, remove the connecting rod caps and lower connecting rod bearing shells and put them in order.
Carefully remove the pistons and connecting rods through the cylinders and place them next to the corresponding connecting rod caps and connecting rod bearing shells.
Remove the main bearing caps together with the lower shells. Remove the crankshaft from the bearing seats. Remove the upper main bearing shells and put them in order.
Disassemble the cylinder head (see above).