GMC Workshop Service and Repair Manuals

Valve: Specifications

Valve Face Angle .........................................................................................................................................................................................................  45°
Valve Head Edge Margin ............................................................................................................................  0.79 mm (Minimum) (0.031 inch Maximum)
Valve Lash ..................................................................................................................................................................................  Net Lash-No Adjustment
Valve Lift (Exhaust) (L35) ........................................................................................................................................................  10.879 mm (0.4280 inch)
Valve Lift (Exhaust) (LF6) ..........................................................................................................................................................  9.887 mm (0.3890 inch)
Valve Lift (Intake) (L35) ...........................................................................................................................................................  10.527 mm (0.4140 inch)
Valve Lift (Intake) (LF6) ...........................................................................................................................................................  10.215 mm (0.4020 inch)
Valve Lifter .............................................................................................................................................................................................  Hydraulic Roller
Valve Rocker Arm Ratio ............................................................................................................................................................................................. 1.5:1
Valve Seat Angle  .........................................................................................................................................................................................................  46°
Valve Seat Runout  ..................................................................................................................................................  0.5 mm Max. (0.002 inch Maximum)
Valve Seat Width: 

(Exhaust) .............................................................................................................................................................  1.575-2.362 mm (0.065-0.098 inch)

Valve Seat Width: 

(Intake)  ................................................................................................................................................................ 0.89 - 1.52 mm (0.035 - 0.060 inch)

Valve Spring Free Length ................................................................................................................................................................... 51.3 mm (2.02 inch)
Valve Spring Installed Height: 

(Exhaust)  ............................................................................................................................................................  42.92-43.43 mm (1.670-1.700 inch)

Valve Spring Installed Height: 

(Exhaust)  ............................................................................................................................................................  42.92-43.43 mm (1.670-1.700 inch)

Valve Spring Pressure (Closed) .....................................................................................................................................................  338-374 N at 42.2 mm

(76-84 lbs. at 1.70 inch)

Valve Spring Pressure (Open) ........................................................................................................................................................  832-903 N at 32.3 mm

(187-203 lbs. at 1.27 inch)

Valve Stem Clearance: 

(Exhaust-Production)  .....................................................................................................................................  0.025-0.069 mm (0.0010-0.0027 inch)

Valve Stem Clearance: 

(Exhaust-Service)  ...........................................................................................................................................  0.025-0.094 mm (0.0010-0.0037 inch)

Valve Stem Clearance: 

(Intake-Production)  ........................................................................................................................................  0.025-0.069 mm (0.0010-0.0027 inch)

Valve Stem Clearance: 

(Intake-Service)  ............................................................................................................................................  0.025-0.0094 mm (0.0010-0.0037 inch)

Valve Stem Oil Seal Installed Height (Measured from the Top of the Large 

Diameter Valve Guide Bevel to the Bottom of the Valve Stem Oil 

Seal ...................................................................................................................................................................... 1-2 mm (0.03937-0.07874 inch)