Inspection After Disassembly

Cylinder Head Bolts Outer Diameter 

• Cylinder head bolts are tightened by plastic zone tightening method. Whenever the size difference between (B) and (A) exceeds the limit, replace them with new one.

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  Limit [(B) - (A) ]

  : Refer to Cylinder Head .

• If reduction of outer diameter appears in a position other than (A), use it as (A) point.

Cylinder Head Distortion 

1. Using a suitable tool, wipe out oil, scale, gasket, sealant and carbon deposits from surface of cylinder head.
   CAUTION: Do not allow gasket fragments to enter engine oil or engine coolant passages.
2. At each of several locations on bottom surface of cylinder head, measure the distortion in six locations

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   Limit

   : Refer to Cylinder Head .

• If it exceeds the limit, replace VVEL ladder assembly & cylinder head assembly.
  NOTE: Cylinder head assembly cannot be replaced as a single part, because it is machined together with VVEL ladder assembly.

Valve Dimensions 

• Check the dimensions of each valve. For the dimensions, refer to Cylinder Head .
• If dimensions are out of the standard.
  • Replace valve and check valve seat contact. Refer to "VALVE SEAT CONTACT".

Valve Guide Clearance 

Valve Stem Diameter

• Measure the diameter of valve stem with suitable tool (A).

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  Standard

  : Refer to Cylinder Head .

Valve Guide Inner Diameter

• Measure the inner diameter of valve guide with suitable tool.

  Standard

  : Refer to Cylinder Head .

Valve Guide Clearance

• (Valve guide clearance) = (Valve guide inner diameter) - (Valve stem diameter)

  Standard

  : Refer to Cylinder Head .

• If the calculated value exceeds the limit.
  • Replace valve (EXH) and/or valve guide (EXH). Refer to Exploded View . (Exhaust side)
  • Replace valve (INT) and/or VVEL ladder assembly & cylinder head assembly. Refer to Exploded View . (Intake side)
    NOTE: Since the valve guide (INT) cannot be replaced by the piece, VVEL ladder assembly & cylinder head assembly replacement are required.

Valve Seat Contact 

• After confirming that the dimensions of valve guides and valves are within the specifications, perform this procedure.
• Apply prussian blue (or white lead) onto contacting surface of valve seat to check the condition of the valve contact on the surface.
• Check if the contact area band is continuous all around the circumference.

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  (A)	: OK
  (B)	: NG

  • If not, grind to adjust valve fitting and check again. If the contacting surface still has "NG" conditions even after the re-check, replace valve seat. Refer to Exploded View .

Valve Spring (with valve spring seat) Squareness 

• Set a suitable tool (A) along the side of valve spring (with valve spring seat) and rotate spring. Measure the maximum clearance between the top of spring and try square.

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  (B)

  : Contact

  Limit

  : Refer to Cylinder Head .

• If it exceeds the limit.
  • Replace valve spring (with valve spring seat). Refer to Exploded View .

Valve Spring Dimensions and Valve Spring Pressure Load 

• Check the valve spring (with valve spring seat) pressure at specified spring height.

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  Standard

  : Refer to Cylinder Head .

• If the installation load or load with valve open is out of the standard.
  • Replace valve spring (with valve spring seat). Refer to Exploded View .