Nissan Pick-ups and Pathfinder 1970-1988

Valve Seats

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REMOVAL & INSTALLATION



Gasoline Engines

See Figures 1, 2, 3, 4 and 5

  1. With the cylinder head removed from the engine and the valves removed from the cylinder head, old valve seat inserts can be removed by boring them out until they collapse. Be careful that the boring doesn't continue beyond the bottom face of the insert recess in the cylinder head.
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  3. Select the suitable valve seat insert and check its outside diameter.
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  5. Machine the cylinder head recess using the center of the valve guide as the center of the valve seat insert so that the insert will have the correct fit.
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  7. Ream the cylinder head recess at room temperature.
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  9. Heat the cylinder head to 302-392°F (150-200°C).
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  11. Fit the insert, making sure that it seats fully in the recess in the cylinder head. Peen the insert with a punch in at least four places equally spaced around its circumference.
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  13. Grind the valve seats to the proper angle.
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  15. Lap the valves with lapping compound to each seat to which they are to be mated. Thoroughly clean both the valves and the seat of all lapping compound before installing the valves.
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Fig. Fig. 1: Bore out the old valve seat until it collapses



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Fig. Fig. 2: Reaming the valve seats



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Fig. Fig. 3: Valve seat replacement



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Fig. Fig. 4: Check the valve seat contact surface



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Fig. Fig. 5: On the diesel, stake the exhaust valve seat in five places with a punch

Diesel Engines
  1. Turn the head upside down in water at 175°F (79°C) while at the same time cool the valve seat in dry ice, for about 5-10 minutes.
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  3. Crack the seat with a cold chisel and remove it.
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  5. Chill the new seats in dry ice and install them in the head. Reface and lap the seats according to specifications.
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