Replacing valve guides Removal

Working from the camshaft side, machine off protruding valve guide sections using a spot facer until the valve guides are flush with the cylinder head. Loosen guide with a sharp hammer blow and press out remainder towards combustion chamber using a press.

Valve Guide Reamer

1761-15

3. Coat machined valve guides with tallow and fit into cylinder head with a shop-made drift, working form the camshaft side.

4. Bore inner valve guide dia. to a dimension of "g" = 8.00 to 8.015 mm using a broach or precision boring equipment. In an emergency, the valve guides may also be machined with a special reamer.

Important: Place and chuck the cylinder in the correct angular position for pressing in and boring the valve guides. After replacing the valve guides, check sealing pattern of valve seats and recut valve seats if required.

1761-15

Installation

The valve guide mounting bores in the cylinder head are widened slightly during removal of the old guides.

When fitting new guides, use oversize valve guides and adjust them accordingly (refer to measurement table).

1. Measure valve guide mounting bores.

2. Machine the outside diameter of the oversize valve guides on a lathe according to the bores in the cylinder head. Guideline for machining: 14.08 - 13.09. The press fit for the inlet and exhaust valve guides must be 0.06 to 0.08 mm.

Valve guide

Outside 0d* of valve guide

Valve guide

Outside 0d* of valve guide

Standard (production) 13.060 1st oversize 13.260

Standard (production) 13.060 1st oversize 13.260

* Machine valve guide 0 d to the respective bore 0 D - observe correct press fit.

Porsche 993 Gauge
How to tell the valve guides apart
Engine Valve Guide Dimensions
1745- 15

Valve dimensions

911 Carrera RS (values in brackets) Inlet valve

Dimension

Inlet valve (sodium-filled)

a

49 ±0.1 mm

(51,5 ±0,1 mm)

b

7.970 - 0.012 mm

c

110.1 ±0.1 mm

a

45°

Valve Guide Puller
1770 - 15

The intake valves of the 911 Carrera (993) and the 911 Carrera RS are sodium-filled!

Exhaust valve

Dimension

Exhaust valve

(b1 - b2 = tapered)

a

42.5 ±0.1 mm

(43.5 ±0,1 mm)

b1

7.950 - 0.012 mm

((7.940 - 0.012 mm)

b2

7.970-0.012 mm

(7.960-0.012 mm

c

109 ±0.1 mm

a

45°

Sodium Filled Valve
1771 - 15

The exhaust valves of the 911 Carrera RS are sodium-filled!

15 65 06 Checking and adjusting installed length of valve springs

Installed length, dimension "A"

1. Assemble shims, valve spring support, valve, auxiliary spring, e.g. for oil thermostat (engine 928), part number 928.107.171.01, valve spring cap and valve keepers.

Note

If required, the spring may be shortened slightly to facilitate assembly.

2. Using a depth gauge, measure vertically from valve spring cap top surface to valve spring seat surface. Record measurement.

Porsche Valve Spring Tool

3. Determine thickness of valve spring cap Record measurement.

Recording Valve Spring Dimensions
1733-15

Installed length, dimension "A"

4. Determine actual dimension

Example for determining the actual dimension:

Inlet valve spring Measured value Thickness of valve spring cap

The value of 36.9 is within the admissible

Note

Take care not to confuse the parts after the measurement.

Engine

Installation dimension specifications Inlet valve A = 36.7 + 0.3 mm

Porsche 911 Bracket Oil Thermostat

15 63 19 Removing and installing valve seal

Removal

Hook special tool 9237 into recess in valve seal and pull valve seal out.

Valve Guide Puller

2204-15

Valve Seal Removal Tool

2204-15

Installation

Install the washers and valve spring seats which have been determined. Push plastic mounting sleeve (8 mm dia.) onto valve stem. Oil seal lip and seat surface of valve seal, position it by hand and knock it carefully onto the valve guide using special tool 9569 (pressure piece). Remove plastic sleeve.

993 Porsche Cam Tools
2203-15

15 03 37 Dismantling and assembling camshaft housings Left-hand camshaft housing

Note: Unless indicated otherwise, coat all aluminum plugs with Optimoly HT (copper paste) and

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