Volkswagen New Beetle. Manual - part 68

 

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Volkswagen New Beetle. Manual - part 68

 

 

Fig. 6: Measuring Valve Stem-to-Guide Clearance 

Lower valve approximately 1/16" below valve seat. Push valve stem against valve guide as far as possible. 
Adjust dial indicator to zero. Push valve stem in opposite direction and note reading. Clearance must be within 
specification.  

If valve guide clearance exceeds specification, valves with oversize stems may be used and valve guides are 
reamed to larger size or valve guide must be replaced. On some applications, a false guide is installed, then 
reamed to proper specification. Valve guide reamer set is used to ream valve guide to obtain proper clearance 
for new valve.  

Reaming Valve Guide 

Select proper reamer for size of valve stem. Reamer must be of proper length to provide clean cut through entire 
length of valve guide. Install reamer in valve guide and rotate to cut valve guide. See Fig. 7 .  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Fig. 7: Reaming Valve Guides 

Replacing Valve Guide 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Replace valve guide if clearance exceeds specification. Valve guides are either pressed, hammered or shrunk in 
place, depending upon cylinder head design and type of metal used.  

Remove valve guide from cylinder head by pressing or tapping on a stepped drift. See Fig. 8 . Once valve guide 
is installed, distance from cylinder head to top of valve guide must be checked. This distance must be within 
specification.  

Aluminum heads are often heated before installing valve guide. Valve guide is sometimes cooled in dry ice 
prior to installation. Combination of a heated cylinder head and cooled valve guide ensures a tight guide fit 
upon assembly. The new guide must be reamed to specification.  

Fig. 8: Typical Valve Guide Remover & Installer 

VALVES & VALVE SEATS 

Valve Grinding 

Valve stem O.D. should be measured in several areas to indicate amount of wear. Replace valve if not within 
specification. Valve margin area should be measured to ensure that valve can be ground. See Fig. 9 .  

If valve margin is less than specification, the valves will be burned. Valve must be replaced. Due to minimum 
margin dimensions during manufacture, some new type valves cannot be reground. Some manufacturers use 
stellite coated valves that must NOT be machined. Valves can only be lapped into valve seat.  

CAUTION: Some valves are sodium filled. Extreme care must be used when 

disposing of damaged or worn sodium-filled valves. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Fig. 9: Measuring Valve Head Margin 

Resurface valve to proper angle specification using valve grinding machine. Follow manufacturer's instructions 
for valve grinding machine. Specifications may indicate a different valve face angle than seat angle. Measure 
valve margin after grinding. Replace valve if not within specification. Valve stem tip can be refinished using 
valve grinding machine.  

Valve Lapping 

During valve lapping of recently designed valves, be sure to follow manufacturer's recommendations. Surface 
hardening and materials used with some valves do not permit lapping. Lapping process will remove excessive 
amounts of the hardened surface.  

Valve lapping is done to ensure adequate sealing between valve face and seat. Use either a hand drill or lapping 
stick with suction cup attached.  

Moisten and attach suction cup to valve. Lubricate valve stem and guide. Apply a thin coat of fine valve 
grinding compound between valve and seat. Rotate lapping tool between the palms or with hand drill.  

Lift valve upward off the seat and change position often. This is done to prevent grooving of valve seat. Lap 
valve until a smooth polished seat is obtained. Thoroughly clean grinding compound from components. Valve-
to-valve seat concentricity should be checked. See VALVE SEAT CONCENTRICITY .  

Valve Seat Grinding 

CAUTION: Valve guides must be in good condition and free of carbon deposits prior 

to valve seat grinding. Some engines contain an induction hardened valve 
seat. Excessive material removal will damage valve seats. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

 

 

 

 

 

 

 

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