Inspection After Disassembly: Notes

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" below.

Valve Guide Clearance

Valve Stem Diameter

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

Standard (Intake and exhaust): Refer to  "CYLINDER HEAD ".

Valve Guide Inner Diameter

• Measure the inner diameter of valve guide with bore gauge.

Standard (Intake and exhaust): Refer to  "CYLINDER HEAD ".

Valve guide clearance

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

  Valve Guide Clearance Standard and limit (Intake and exhaust): Refer to  "CYLINDER HEAD ".

• If the calculated value exceeds the limit, replace valve and/or valve guide. When valve guide must be replaced, refer to "DISASSEMBLY AND ASSEMBLY ".

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.
• If not, grind to adjust valve fitting and check again. If the contacting surface still has "NG" (B) conditions even after the recheck, replace valve seat. Refer to "DISASSEMBLY AND ASSEMBLY ".
  Fig 2: Identifying Valve Seat OK And NG Condition

  Courtesy of NISSAN NORTH AMERICA, INC.

Valve Spring Squareness

• Set a try square (A) along the side of valve spring and rotate spring. Measure the maximum clearance between the top of spring and try square.
  Fig 3: Identifying Maximum Clearance Between Top Of Spring And Try Square

  Courtesy of NISSAN NORTH AMERICA, INC.

  Limit: Refer to  "CYLINDER HEAD ".

• If it exceeds the limit, replace valve spring.

Valve Spring Dimensions and Valve Spring Pressure Load

• Check the valve spring pressure at specified spring height.

  Standard (Intake and exhaust): Refer to  "CYLINDER HEAD ".

  Free height 

  Installation height 

  Installation load 

  Height during valve open 

  Load with valve open 

• If the installation load or load with valve open is out of the standard, replace valve spring.
  Fig 4: Checking Valve Spring Dimensions And Valve Spring Pressure Load

  Courtesy of NISSAN NORTH AMERICA, INC.