Characteristics of the valve timing mechanism (BMW 3 Series E21)

The engine uses a valve timing mechanism with an overhead camshaft, which is driven by a toothed belt from a toothed pulley mounted on the crankshaft.

Valve timing

Camshaft

The camshaft has seven bearings.



Clearance between camshaft journals and bearing holes, mm: 0.059–0.1.

Axial clearance of camshaft, mm: 0.2.

Timing Belt for Camshaft Drive

Brands and type: Pirelli 111 R 254 or Gates 6017.
Number of teeth: 111.
Belt width, mm: 25.4.

Belt tension is provided by a mechanical tensioner from FAG, INA or SKF.

End runout of the belt on the side guide at a diameter of 52 mm, mm: 0.3.

Radial runout of the belt, mm: 0.2.

Number of teeth:

• camshaft pulley (catalog N 12 64 532): 42;
• intermediate shaft pulley (catalog N 1 265 458): 28;
• crankshaft pulley (catalog N 1264 5313): 21.

Intermediate shaft

The drive of the two-support intermediate shaft is carried out from the crankshaft by a toothed belt. A 12-tooth gear for driving the oil pump and ignition distributor is installed on the rear end of the intermediate shaft. On carburetor engines, the intermediate shaft drives the fuel pump through a cam.

Diameter of bearing journals, mm:

• on "320": 38.0^-0,009_-0,025;
• on "323i": 36.5^-0,009_-0,025;

Outer diameter of oil pump and distributor drive gear, mm: 18.0^+0,048_+0,035;

Diameter of the hole for the gear drive of the oil pump and ignition distributor, mm: 18^-0,005_-0,023;