Dodge Nitro. Manual - part 101

 

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Dodge Nitro. Manual - part 101

 

 

is a one-piece forging, while the exhaust valve has a forged head with a welded stem for lock groove hardness. 
The four valves (two intake and two exhaust) employ a three-groove lock design to help facilitate valve 
rotation. 

OPERATION 

VALVES 

The intake valve allows the air/fuel mixture to enter the combustion chamber. The exhaust valve allows the 
burned air/fuel mixture to exit the combustion chamber. Also, the intake and exhaust valves seal the combustion 
chamber during the compression and power strokes. 

STANDARD PROCEDURE 

VALVE AND VALVE SEAT REFACING 

Fig. 145: Intake & Exhaust Valves 
Courtesy of CHRYSLER LLC 

1 - MARGIN
2 - FACE

 

2007 Dodge Nitro R/T 

2007 ENGINE 4.0L - Service Information - Nitro

  

VALVES 

1. Inspect the remaining margin (1) after the valves are refaced. See SPECIFICATIONS.  

VALVE SEATS 

Fig. 146: Valve Face & Seat 
Courtesy of CHRYSLER LLC 

1. When refacing valve seats, it is important that the correct size valve guide pilot be used for reseating 

stones. A true and complete surface must be obtained.  

2. Measure the concentricity of valve seat using dial indicator. Total runout should not exceed 0.051 mm 

(0.002 inch.) Total indicator reading.  

3. Inspect the valve seat (3) with Prussian blue to determine where the valve (1) contacts the seat. To do 

this, coat valve seat (1) LIGHTLY with Prussian blue then set valve in place. Rotate the valve with light 
pressure. If the blue is transferred to the center of valve face (2), contact is satisfactory. If the blue is 
transferred to top edge of valve face (2), then lower valve seat (3) with a 15° stone. If the blue is 
transferred to the bottom edge of valve face (2), then raise valve seat (3) with a 65° stone. 

3 - STEM
4 - VALVE SPRING RETAINER LOCK GROOVES

1 - SEAT WIDTH
2 - FACE ANGLE
3 - SEAT ANGLE
4 - SEAT CONTACT AREA

NOTE:

Valve seats (1) which are worn or burned can be reworked, provided that 
correct angle and seat width (1) are maintained. Otherwise cylinder head 

 

2007 Dodge Nitro R/T 

2007 ENGINE 4.0L - Service Information - Nitro

  

4. When seat is properly positioned the width of the intake seats should be 0.75 to 1.25 mm (0.0296 to 

0.0493 in.) and exhaust seats should be 1.25 to 1.75 mm (0.049 to 0.069 in.). See Fig. 146.  

VALVE AND SPRING INSTALLED HEIGHT 

Fig. 147: Checking Valve Tip Height & Valve Spring Installed Height 
Courtesy of CHRYSLER LLC 

1. Coat valve stems with clean engine oil and insert them in cylinder head.  

2. If valves or seats have been refaced, check valve tip height (A). See Fig. 147. If valve tip height is greater 

than 43.65 mm (1.7185 in.) intake or 46.48 mm (1.8299 in.) exhaust, grind valve tip until within 
specifications. Make sure measurement is taken from cylinder head surface to the top of valve stem.  

3. Install valve seal/spring seat assembly over valve guides on all valve stem. See Fig. 149. Ensure that the 

garter spring is intact around the top of the rubber seal. 

must be replaced.

1 - SPRING RETAINER
2 - GARTER SPRING
3 - VALVE SPRING SEAT TOP
4 - CYLINDER HEAD SURFACE

 

2007 Dodge Nitro R/T 

2007 ENGINE 4.0L - Service Information - Nitro

  

Fig. 148: Valve Spring Identification 
Courtesy of CHRYSLER LLC 

4. Place valve spring (color-coded end facing up). See Fig. 148 and valve retainer into position on spring 

seat. See Fig. 147

1 - YELLOW OR WHITE DYE
2 - ORANGE DYE

 

2007 Dodge Nitro R/T 

2007 ENGINE 4.0L - Service Information - Nitro

  

 

 

 

 

 

 

 

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