Valve Guide: Service and Repair

Specifications:

Valve guides:

Association engines - guide sleeves - broaches:

NOTE: In the event of repairs, cylinder heads with standard normal dimension valve guides must be fitted with standard dimension valve guides (grey-brown). First, ream basic bores with reamers 14.035 mm dia. (intake) and 15.035 mm dia. (exhaust) to avoid too great an overlap.

Basic bores in which the use of standard dimension value guides do not provide an adequately tight seat (minimum interference 0.007 mm) must be machined with broaches for repair stage valve guide installation.

The broaches must be driven through the basic bores with a plastic hammer and the aid of guide sleeves.


Checking Valve Guides:




With cylinder head removed, check valve guides by means of plug gauge in longitudinal and transverse direction.

Valve guides which accept the no-go end with the wear limit (+220) in its entire height (5 mm) must be renewed.

Valve guides which are worn outside on the valve stem seal seat so that the valve stem seal is no longer seated tightly, should also be replaced.


Replacing Valve Guides:








1 Knock out valve guide from combustion chamber end by means of knocking mandrel.
2 Check valve guide basic bore with plug gauge in longitudinal and transverse direction.
Basic bores into which the measuring plug can be inserted at one point for its entire height (8 mm), must be finished to repair stage dimensions.
If the measuring plug cannot be inserted fully or only in part, the basic bore for the valve guide can be reamed to normal dimension for the valve guides.

Machining Basic Bore:





Standard dimension
3 Ream basic bore with reamer 14.035 mm dia. or 15.035 mm dia. while lubricating with kerosene.
Ream with low pressure and do not cant the reamer.

NOTE: Handle reamers carefully and put back into protective sleeve so that the cutting edges are not damaged.

Repair stage
4 Remove all soot from cylinder head and clean, in particular the inside of the valve seat rings.
5 Remove metal chips (use stiff plastic brush or similar) from the cutting edges of the broach prior to use.
6 Select correct guide sleeve (refer to table). Make sure that the guide sleeve is centered only by the inner diameter of the valve seat ring concerned and is not impaired with carbon residue, casting projections, intake and exhaust port walls etc.





7 Liberally lubricate guide sleeve, basic bore and the entire broach with engine oil.
8 Introduce broach in the direction of broaching into the guide sleeve so that during the subsequent introduction of the guide sleeve into the cylinder head the broach will enter into the bore up to the first cutting edge. Center the sleeve in the valve seat ring by means of rotary movements.





9 Drive broach through the bore by means of an aluminum mandrel approx. 130 mm long and a plastic hammer of approx. 250 g.


Inserting Valve Guide:





10 Cool valve guide in liquid nitrogen (approx. 3 minutes) and insert.
If no liquid nitrogen is available, heat cylinder head in a water bath to approx. 80 °C. Drive valve guide into the cylinder head by means of the installing mandrel until the locking ring contacts the cylinder head.
11 Check valve guide for tight seat with the cylinder head in a cooled-down condition.





12 Check inner dia. of valve guide with plug gauge.
The entire go end should be introduced into the bore.





13 If required, ream inner dia. with reamer.
14 Check valve seats for runout and refinish if required.