Combustion chamber volume, cm3:
- «315», «316» (from model year 1981): 57,7±1;
- «3181»: 59,5± 1.
Cylinder head height, mm: 129.0±1.
Reducing the height of the cylinder head during grinding, mm, no more: 0.5 (in this case, it is necessary to grind the cover of the timing mechanism by the same amount).
Valve seats
The valve seats are plug-in, 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 model car engines «315», «316» up to 1980 model year inclusive and on engines of car models «316» from model year 1981, «318», «318i», «320», «320i», are not interchangeable.
Nominal thickness of gaskets, mm: 1.2. Spare parts are supplied with gaskets with a thickness increased by 0.3 mm.
Valve guides
The valve guides are made of special cast iron and are pressed into the cylinder head. The parameters of the guide bushings of the intake and exhaust valves of all engines are the same. The valve guides are pressed into the cylinder head heated to a temperature of 220-250°C.
Valve guide specifications
- 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 seat diameter, mm: 140-0.018
- Increased repair dimensions, mm: 14.1; 14.2; 14.3.
- The protrusion of the 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 exhaust valve stems are chrome-plated.
The gap between the rocker arm and the valve stem is adjusted by rotating the eccentric with the lock nut located on the rocker arm.
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 0.15-0.20 mm for intake and exhaust valves.
Note. From model year 1981, intake and exhaust valve clearances on a cold engine for «316» are equal to 0.20±0.025 mm, and for «318» - 0.20-0.25 mm.
Frequency of check and adjustment: every 15 thousand kilometers.
Valve springs
Each intake and exhaust valve is equipped with one spring. The valve springs are installed with the color mark down towards the cylinder head.
Characteristics of intake and exhaust valve springs
Valve rocker arms
Rocker arms are made of light alloy and are the same for intake and exhaust valves. The contact points of the rocker arms with the camshaft cams are made of high-hardness cast iron.
- Rocker hole diameter, mm: 15.5+0.0180
- Rocker axle diameter, mm: 15.5-0.016-0.034
- The diameter of the holes in the cylinder head for the axes of the rocker arms, mm: 15.5 + 0.043.
- Mounting clearance of the rocker axes in the cylinder head, mm: 0.016-0.077.
- Gap between rocker arms and axle, mm: 0.016-0.052.