Cylinder head characteristics (BMW 3 Series E21)

The cylinder head is cast from aluminum alloy. The head has three-spherical combustion chambers. The valve seats and guide bushings are pressed into the cylinder head.

Combustion chamber volume, cm³:

• "315", "316" (since 1981 model year): 57,7±1;
• "3181": 59,5± 1.

Cylinder head height, mm: 129.0±1.

Reduction in cylinder head height during grinding, mm, no more than: 0.5 (in this case it is necessary to grind the distributor cover to the same extent).

Valve seats

The valve seats are insertable; after cooling to a temperature of minus 70°C, the seats are pressed into the cylinder head, heated to a temperature of 220-250°C.

Cylinder head gaskets

Cylinder head gaskets used on engines of cars of the following models: "315", "316" up to and including the 1980 model year and on engines of "316" model cars from the 1981 model year, "318", "318i", "320", "320i", are not interchangeable.



Nominal thickness of gaskets, mm: 1.2. Gaskets with a thickness increased by 0.3 mm are supplied as spare parts.

Valve guide bushings

The valve guides are made of special cast iron and pressed into the cylinder head. The parameters of the inlet and outlet valve guides are the same for all engines. The valve guides are pressed into the cylinder head heated to a temperature of 220-250°C.

Valve guide bushing characteristics

• Length, mm: 52.0.
• Outer diameter, mm: 14^+0,044_+0,043
• Repair dimensions, mm: +0.1; +0,2; +0,3.
• Inner diameter, mm: 8^+0,015₀
• Cylinder head socket diameter, mm: 14⁰_-0.018
• Increased repair dimensions, mm: 14.1; 14,2; 14,3.
• Protrusion of valve guide bushings relative to the plane of the cylinder head, mm: 15±0.5.

Valves

The valves are located in the cylinder head in a V-shape, the stems of the exhaust valves are chromed.

The clearance between the rocker arm and the valve stem is adjusted by rotating the eccentric with a lock nut located on the rocker arm.

Clearances in the valve drive mechanism

The normal clearance between the rocker arm eccentric and the end of the valve stem, measured with a feeler gauge on a cold engine, is 0.15-0.20 mm for intake and exhaust valves.

Note: Since the 1981 model year, the clearances in the intake and exhaust valve drives on a cold engine for the "316" are 0.20±0.025 mm, and for the "318" - 0.20-0.25 mm.

Frequency of inspection and adjustment: every 15 thousand km.

Valve springs

Each intake and exhaust valve is equipped with one spring. Valve springs are installed with the color mark facing down, towards the cylinder head.

Inlet and outlet valve spring characteristics

Valve drive rocker arms

The rocker arms are made of light alloy and are the same for the intake and exhaust valves. The contact points of the rocker arms with the camshaft cams are made of high-hardness cast iron.

• Rocker arm hole diameter, mm: 15.5^+0,018₀
• Rocker shaft diameter, mm: 15.5^-0,016_-0,034
• Diameter of holes in the cylinder head for rocker arm axles, mm: 15.5+0.043.
• Installation clearance of rocker arm axles in cylinder head, mm: 0.016-0.077.
• Clearance between rocker arms and axle, mm: 0.016-0.052.

Information obtained from this online resource: «BMWMAN.ru»