Measure the alignment of the centers of the holes of the connecting rod heads, the distance "A" between which should be within 150-0.04 mm, and the longitudinal bend "B" of the connecting rod rod, which should not exceed 0°-30'.
Make sure that the connecting rods belong to the same weight group: connecting rods without bearing shells should not differ from each other in weight by more than ±4 g. The connecting rod weight groups are marked with paint.
When erasing the marks, compare the connecting rods by weight, using one of them as a reference.
When connecting the piston to the connecting rod, it is necessary that the piston pin, lubricated with engine oil, enters the hole in the bushing of the upper head of the connecting rod by simply pressing with the thumb.
Wipe the crankshaft journals dry. Place a piece of plastic calibrated wire on the surface of the journal. Install the connecting rod with the cap on the journal and tighten the nuts of the previously used connecting rod bolts.
Remove the cover and, using the scale on the packaging and by flattening the wire, determine the size of the gap between the bearing shell and the connecting rod journal.
Lubricate the connecting rod journal with engine oil and install the connecting rod with the cap on the journal.
Tighten the nuts of the new connecting rod bolts to a torque of 2.0 kgf·m, then turn them an additional 70°.
(Information taken from this resource «BMWMan.ru»)