Valve timing specifications (BMW 5 Series E12)

The engine uses a valve timing mechanism with an overhead camshaft, the drive of which is carried out by a double-row roller chain or a toothed belt (BMW "520" from the 1978 model year and "520i" from the 1982 model year). The covers of the timing mechanism drive are cast from an aluminum alloy. The chain tension is adjusted by an automatic tensioner with a hydraulic shock absorber and a lock. The tension of the toothed belt is adjusted automatically.

Covers of the drive of the timing mechanism of engines of automobile models "518", "520", "520i" differ from the covers on the models "525" and "528".

Valve timing (with a calculated clearance of 0.50 mm between the rocker arm tip and the camshaft back)

* Tolerance +2.50°.

Total opening angle of intake and exhaust valves: 236°.

Lift of intake and exhaust camshaft lobes, mm:

• "518", "520", "5201": 7,0267±0,080;
• "525", "528": 6,8471;
• "528i": 7,4228;
• "520" since 1978 model year, "520i" since 1982 model year: 6.850+0.08.

Number of camshaft sprocket teeth: 26.

Number of teeth on crankshaft sprocket: 13.

Number of chain links: 94.

Since model year 1978, the chain tensioner plunger length is 61.8+0.2 mm.

Valve timing on the "528" and "528i" models (with a calculated clearance between the rocker arm tip and the cam back of 0.50 mm)

Intake valve timing before TDC of exhaust stroke with advance: 14°.

Intake valve closing after BDC of compression stroke with delay: 54°.

Start of opening of the exhaust valve before BDC of the working stroke with advance: 54°.

Closing of the exhaust valve after TDC of the exhaust stroke with a delay of 14°.

Total opening angle of the intake and exhaust valves: 248°.

Installation of the valve timing mechanism

Since model year 1978 on BMW "525", "528" and "528i" the following features must be taken into account.

Marking of camshafts:

• "525": mark "1, 260°";
• "528" and "5282": "3, 272°" mark.

When removing the camshaft, check the clearance between the mounting flange and the camshaft and replace the mounting flange if necessary.

Valve timing (with a calculated clearance between the rocker arm tip and the cam back of 0.30 mm)

BMW "520" from 1978 model year and "520i" from 1982 model year

Start of opening of the intake valve before TDC of the exhaust stroke with advance: 22°.

Intake valve closing after BDC of compression stroke with delay: 58°.

Start of opening of the exhaust valve before BDC of the working stroke with advance: 62°.

Closing of the exhaust valve after TDC of the exhaust stroke with a delay of 18°.

Camshaft

The camshaft is three-bearing ("518", "520", "5202") or four-support ("525", "528", "528i", "535i").

Camshaft characteristics

Note: The axial clearance of the camshaft of the BMW "520" engine from the 1978 model year and "520i" from the 1982 model year is 0.20 mm.

(The original text of the article is available on the resource: BMWman.ru)