Honda Accord/Prelude 1984-1995 Repair Guide

Valves

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REMOVAL & INSTALLATION



See Figures 1, 2, 3 and 4

This procedure requires the use of a valve spring compressor. This common tool is available at most auto supply stores. It may also be possible to rent one from a tool supplier. It is absolutely essential that all components be kept in order after removal. Old ice trays make excellent holders for small parts. The containers should be labeled so that the parts may be reinstalled in their original location. Keep the valves in numbered order in a holder such as an egg carton or an inverted box with holes punched in it. Label the container so that each valve may be replaced in its exact position. (Example: Exhaust No. 1, No. 2, etc.)

  1. Following the procedures outlined in this section, remove the head from the engine then remove the rocker arms and camshaft.
  2.  
  3. Compress the valve spring (using a valve spring compressor) and remove the keepers at the top of the valve.
  4.  



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Fig. Fig. 1: Be careful not to lose the valve keepers

  1. Slowly release the tension on the compressor and remove it. Remove the spring retainer (upper cap), the valve spring, the valve stem oil seal and the lower spring seat. Keep the springs in their correct orientation; they must be reinstalled exactly as they were, not upside down.
  2.  
  3. The valve is then removed from the bottom of the head.
  4.  
  5. Repeat for each valve in the head, keeping them labeled and in order.
  6.  
  7. Thoroughly clean and decarbon each valve. Inspect each valve and spring as outlined later in this section.
  8.  



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Fig. Fig. 2: Carefully scrape the carbon from the valve

To install:
  1. Lubricate the the valve stem and guide with clean engine oil. Install the valve in the cylinder head and position the lower spring seat.
  2.  
  3. Lubricate the new valve stem seal with clean engine oil and install it.
  4.  



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Fig. Fig. 3: Always use new valve stem seals

  1. Install the valve spring and the upper seat, compress the spring and install the two keepers. Relax tension on the compressor and make sure everything is properly placed. Tap the spring retainer of the installed valve with a plastic mallet to ensure proper locking of the retainers.
  2.  



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Fig. Fig. 4: Lightly tap the spring retainer of the installed valve with a plastic mallet to ensure proper locking of the retainers

  1. Complete the reassembly of the head by installing the camshafts and rocker arms. Refer to the procedures in this section.
  2.  

INSPECTION AND LAPPING



See Figures 5, 6, 7, 8 and 9

Accurate measuring equipment capable of reading to 0.0001 (ten thousandths) inch is necessary for this procedure.

Inspect the valve faces and seats for pits, burned spots, and other evidence of poor seating. The valve can be refaced to remove pits and carbon. If the valve is in such poor shape that refacing it will reduce the margin thickness out of specification, discard the valve. Never try to straighten and reuse a bent valve. It is recommended that any seat resurfacing or valve refacing be done by a reputable machine shop.



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Fig. Fig. 5: Valve stems may be rolled on a flat surface to check for bends

Check the valve stem for scoring and/or burned spots. If the stem and head are in acceptable condition, clean the valve thoroughly with solvent to remove all gum and varnish.

Use the micrometer to measure the diameter of the valve stem. Compare the reading to the Valve Specifications Chart. If not within specification, replace the valve.



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Fig. Fig. 6: Measure the valve stem at these points with a micrometer

The valve head margin thickness should be checked both before and after refacing. If at any time it is below the minimum thickness specification, it must be replaced. The specifications are as follows:



Accords through 1989 and Preludes through 1991-Intake: 0.045 in. (1.15mm) Exhaust: 0.057 in. (1.45mm)
 
1990-95 four cylinder Accords-Intake: 0.026 in. (0.65mm) Exhaust: 0.037 in. (0.95mm)
 
Accord V-6-Intake: 0.045 in. (1.15mm) Exhaust: 0.057 in. (1.45mm)
 
1992-95 Preludes with SOHC engines-Intake: 0.026 in. (0.65mm) Exhaust: 0.037 in. (0.95mm)
 
1992-95 Preludes with DOHC engines (except VTEC)-Intake: 0.026 in. (0.65mm) Exhaust: 0.033 in. (0.85mm)
 
1992-95 Preludes with DOHC VTEC engines-Intake: 0.033 in. (0.85mm) Exhaust: 0.057 in. (1.45mm)
 



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Fig. Fig. 7: If the margin thickness is less than specified, replace the valve

Check the top of each valve stem for pitting, mushrooming and unusual wear due to improper rocker adjustment, etc. The stem tip can be ground flat if it is worn, but very little can be removed. If more than just a touch of grinding is needed to make the tip flat and square, the valve must be replaced. If the valve stem tips are ground, make sure you fix the valve securely into a jig designed for this purpose. The tip must contact the grinding wheel squarely at exactly 90 degrees. Most machine shops that handle automotive work are equipped for this job.



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Fig. Fig. 8: The stem tip can be ground flat if it is worn, but very little can be removed

The valves should also be checked for proper seat contact.

  1. Apply a thin coat of prussian blue (or white lead) to the valve face and place the valve in the head.
  2.  
  3. Apply light pressure to the valve, but do not rotate it.
  4.  
  5. Carefully remove the valve from the head then check the valve and seat. If blue appears 360 degrees around the valve seat, the seat and valve are concentric.
  6.  
  7. Check that the seat contact is in the middle of the valve face.
  8.  
  9. If the valve and seat are not concentric or the seat contact is not in the middle of the valve face, you should consult a reputable machine shop for proper refacing.
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  11. After machine work has been performed on valves/seats, it may be necessary to lap the valves to assure proper contact. For this, you should first consult your machine shop to determine if lapping is necessary. Some machine shops will perform this for you as part of the service, but the precision machining which is available today often makes lapping unnecessary. Additionally, the hardened valves/seats used in modern automobiles may make lapping difficult or impossible. If your machine shop recommends that you lap the valves proceed as follows:
    1. Coat the valve face and seat with a light coat of valve grinding compound. Attach the suction cup end of the valve grinding tool to the head of the valve (it helps to moisten it first).
    2.  
    3. Rotate the tool between the palms, changing position and and lifting the tool often to prevent grooving. Lap in the valve until a smooth, evenly polished surface is evident on both the seat and face.
    4.  
    5. Remove the valve from the head. Wipe away all traces of grinding compound from the surfaces. Clean out the valve guide with a solvent-soaked rag. Make sure there are NO traces of compound in or on the head.
    6.  
    7. Proceed through the remaining valves, lapping them one at a time to their seats. Clean the area after each valve is done.
    8.  
    9. When all the valves have been lapped, thoroughly clean or wash the head with solvent. There must be NO trace of grinding compound present.
    10.  

  12.  



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Fig. Fig. 9: Hand lapping the valve and seat

REFACING



Due to the skill involved and the high cost of purchasing the proper equipment, it is recommended that valve refacing be handled by a reputable machine shop.

 
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