On the model «518», from chassis no. 4 625 659, on the model «520», starting from chassis no. 4 712 954, on the model «520i», starting from chassis no. 4 453 077, the design of the combustion chambers has been changed in order to unify them with the models «525» And «528».
Cylinder head height, mm: 129±0.1.
Reducing the height of the cylinder head during grinding, no more than, mm: 0.5 (in this case, it is necessary to grind the cover of the timing mechanism by the same amount).
Since the 1980 model year, the following minimum height of the cylinder head after grinding has been established, mm: «518»: 128,6; «525»: 128,6; «528i»: 128,6; «535i»: 128,6.
Permissible cylinder head height after grinding («520» from model year 1978, «520i»), not less than, mm: 124.7.
Cylinder head gasket
Cylinder head gasket only installs in one position, dry, except at the front (camshaft drive side), to which to apply a sealant such as «Atmosit» or «Kuril K2».
On the model «520i» reinforced metal lining of the cylinder head gasket. This type of gasket can also be applied to the carburetor engine of the car model «520». It is not allowed to install the cylinder head gasket of the carburetor engine of the model «520» on the model engine «5201» with fuel injection. Gasket thickness (not compressed), mm: 1.2.
Valve seats
Valve seats are plug-in.
Characteristics of valve seats of the engine model «518»
Characteristics of the valve seats of the engine models «520», «520i», «525», «528»
* «525»: 1.60-2.00 mm.
** «525»: 2.00-2.40 mm.
From model year 1978 on BMW models «525», «528» And «528i» The following characteristics of valve seats have been changed.
Working chamfer width, mm:
- intake valves: 1.6-2.0;
- exhaust valves: 2.0-2.4.
Angle of chamfer of intake and exhaust valves: 45°30'+20'.
Since model year 1980, new valve seat sizes have been introduced
From model year 1982 on BMW «518i» the outer diameter of the inlet valve seats and the diameter of the seat seats are 47.35 and 47.35 H7 mm, respectively. When repairing, the dimensions increase by 0.20 mm. bmw «520» from model year 1978 and «520i».
Outer diameter of seats, mm: inlet valves: 42.35; exhaust valves: 37.85.
Repair size of saddles, mm: +0.20.
Seat seat diameter, mm: inlet valves: 42.35 H7; exhaust valves: 37.85 H7.
Chamfer angle: 45°.
Width of the working chamfer, mm: inlet valves: 1.6-2.0; graduation: 2.0-2.4.
Valve guides
The valve guides are made of special cast iron and are pressed into the cylinder head. The dimensions of the guide sleeves for the intake and exhaust valves are the same.
Valve guide specifications for all models
Since 1978 modal year on models «525», «528» And «528i» tightness when pressing the valve guide bushings into the cylinder head, mm: 0.015-0.044.
Since the 1980 modal year, the following characteristics have changed.
Length (for ace models), mm: 50.5.
Outer diameter of guide sleeves/diameter of seat in cylinder head (for all models) mm: 14/14 H7.
Inner diameter (for all models), mm: 8 H7.
The protrusion of the guide bushings relative to the plane of the cylinder head, mm: «518»: 15; «525», «528i» And «5351»: 13,5.
Characteristics of valve guides for «520» from model year 1970 and «520i».
Length, mm: 45.
Inner diameter, mm: 4 H7.
The protrusion of the bushings relative to the plane of the cylinder head, mm: 14.5.
The outer diameter of the sleeve / the diameter of the socket in the cylinder head, mm: 13/13 H7.
Repair dimensions: 1st: increased by 0.1 mm; 2nd: enlarged by 0.2 mm; 3rd: enlarged by 0.3 mm.
Heating temperature of the cylinder head when pressing in the guide bushings,°С: 220-250.
Valves
The valves are made of special steel, the stems are chrome-plated. In the cylinder head, the valves are arranged in a V-shape and are actuated from above by a non-located camshaft.
Valve specifications
* Values in brackets are for BMW «525» And «528».
Clearances in the valve drive mechanism
The normal clearance between the rocker eccentric and the end of the valve stem, measured with a feeler gauge on a cold engine, is for intake and exhaust valves on «518», «520», «520i» 8.15-6.20 mm, on «525», «528» - 0.25-0.30 mm.
From model year 1978 on «525», «528» And «528i» some characteristics of the valves have been changed.
Total length of valves, mm:
- intake: 106.5±0.2;
- graduation: 107.5±0.2.
Nominal height from the plate to the chamfer of the valve head, mm:
- intake: 1.5±0.15;
- graduation: 2.2±0.1.
Minimum height of the edge of the valve head, mm:
- intake: 1.2;
- graduation: 1.9.
Maximum allowable distortion between the working chamfer and the inlet and outlet valve stem, not more than, mm: 0.02.
Nominal clearance between guide bushings and valve stems, mm:
- intake: 0.025-0.055;
- graduation: 0.040-0.070.
Maximum allowable clearance (when worn), mm: 0.15.
For model year 1980, the following features have changed for all models.
Minimum valve head height, mm:
- intake: 1.3;
- graduation: 2.0.
Maximum allowable clearance between valve guides and valve stems (when worn), mm: 0.15.
BMW «520» from model year 1978 and «520i»
The minimum height of the edge of the valve head after grinding, mm:
- intake valves: 1.3;
- exhaust valves: 2.0.
Maximum allowable clearance between valve guides and valve stems (when worn), mm: 0.15.
Clearances in the valve drive mechanism
Normal clearance between the rocker eccentric and the end of the valve stem, measured with a feeler gauge on a cold engine (oil temperature 35°C), is 0.25 mm for intake and exhaust valves.
Valve springs
Valve springs are the same for intake and exhaust valves. The springs are installed with the color mark down and towards the cylinder head.
Valve spring specifications
From model year 1978 on «525», «528» And «528i» the length of the springs is 37.6 mm under a load of 28.45 kgf and 28.5 mm under a load of 68.67 kgf.
Valve rocker arms
The rocker arms are made of light alloy, the contact points of the rocker arms with the camshaft cams are made of cast iron of increased hardness.
Rocker hole diameter, mm: 15.5+0-0.018.
Rocker axle diameter, mm: 15.5-0.016-0.034.
Gap between rocker arms and axle, mm: 0.016-0.077.
From model year 1978 on «525», «528» And «528i» the rocker arm bore diameter is 15.5+0.043, the gap between the rocker arms and the axle is 0.016-0.052 mm.
The latest change applies to all models from MY 1980 onwards.
BMW «520» from model year 1978 and «520i»
Gap between rocker arms and axle, mm: 0.010-0.052.