Replacing Valve Guides

1.Clean cylinder head and check. If the valve seats or mating faces of the cylinder heads cannot be remachined, the cylinder heads are not suitable for replacement valve guides.

2.Position cylinder head on press-out base.

3.Working from the camshaft side to the combustion-chamber side, press out valve guides with a press.

5.Machine KD valve guide, part no. 944 104 327 51 (external diameter 11.26 mm) to correct size.

Loading must be 0.06 - 0,08 mm for both intake and exhaust valve guides.

Example:

Bore in cylinder head measured 11.020 mm. Machine outside diameter of KD valve guide to 11.080 or 11.10 mm.

4.Use internal calipers to measure bores in cylinder head.

Note:

Replacing valve guides, ENGINE TYPE M 28. 41/42, '87 MODELS ONWARD

It is essential to place a 1 mm thick washer on the cylinder-head mating face before installing the valve guide.

6.Heat cylinder head to 170°C. Coat valve guides with talcum powder, tap lightly into position, align and, using a thrust piece and working from the camshaft side, press into cylinder head until seated.

Caution:

Do not maintain the temperature of 170°C for more than a maximum of 90 minutes.

7.Roughen valve guides with Special Tool 3120.

Proceed as follows:

It is essential to use petroleum as a lubricant when roughening valve guides. During this operation, withdraw reamer frequently to remove chips. Once bore has been reamed, finish with dry reamer.

8.The valve-seat rings must be remachined when the valve guides have been replaced, it is not sufficient to grind in the valves with grinding paste.

Note:

Distinguishing feature, cylinder head

185/'86 models M 28.43/44/45/46

Bearing bridge attachment, M 6

Exhaust manifold attachment 2-bolt flange

'87 models onward M 28.41/42

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