Chrysler Front Wheel Drive Cars 4-CYL 1981-1995 Repair Information

Valve Lash

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ADJUSTMENT



Valve adjustment determines how far the valves enter the cylinder and how long they stay open and closed.

If the valve clearance is too large, part of the lift of the camshaft will be used in removing the excessive clearance. Consequently, the valve will not be opening as far as it should. This condition has two effects: the valve train components will emit a tapping sound as they take up the excessive clearance and the engine will perform poorly because the valves don't open fully and allow the proper amount of gases to flow into and out of the engine.

If the valve clearance is too small, the intake valve and the exhaust valves will open too far and they will not fully seat on the cylinder head when they close. When a valve seats itself on the cylinder head, it does two things: it seals the combustion chamber so that none of the gases in the cylinder escape and it cools itself by transferring some of the heat it absorbs from the combustion in the cylinder to the cylinder head and to the engine's cooling system. If the valve clearance is too small, the engine will run poorly because of the gases escaping from the combustion chamber. The valves will also become overheated and will warp, since they cannot transfer heat unless they are touching the valve seat in the cylinder head.

While all valve adjustments must be made as accurately as possible, it is better to have the valve adjustment slightly loose than slightly tight as a burned valve may result from overly tight adjustments.

2.2L and 2.5L Engines

See Figure 1

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Fig. Fig. 1: The 2.2L engine utilizes hydraulic lash adjusters and requires no manual valve lash adjustment

The 2.2L and 2.5L engines (except Premier 2.5L engine) use hydraulic lash adjusters. No periodic adjustment or checking is necessary.

The Premier 2.5L engine utilizes hydraulic valve tappets and the rocker arms are bolted to the cylinder head with a pre-determined amount of torque. The lash on these engines is not adjustable. If the valvetrain makes noise as if the valve lash is out of adjustment, there is a defect with one of the components (such as a bleeding down valve tappet, a bent pushrod, loose rocker arm mounting bolt, etc.).

2.6L Engine

See Figures 2, 3 and 4

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Fig. Fig. 2: When adjusting the jet valve lash, remember that the jet valve spring is easy to depress and a false reading is possible



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Fig. Fig. 3: Once the correct lash is achieved, hold the adjusting screw while tightening the locknut



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Fig. Fig. 4: When installing the rocker arm cover, make sure to apply sealant as shown to prevent oil leaks

The 2.6L engine has a jet valve located beside the intake valve on each cylinder. The valve arrangement on the 2.6L is simple: the intake valves and smaller jet valves are on the left-hand (radiator) side of the engine and the exhaust valves are on the right-hand (firewall) side of the engine. The cylinders are numbered 1 through 4 from the front (crankshaft pulley side) to the back (transaxle) end of the engine.

When adjusting valve clearances, the jet valve must be adjusted before the intake valve.

  1. Start the engine and allow it to reach normal operating temperature.
  2.  
  3. Stop the engine and remove the air cleaner and its hoses. Remove any other cables, hoses, wires, etc., which are attached to the valve cover, and remove the valve cover.
  4.  
  5. Disconnect the high tension coil-to-distributor wire at the coil.
  6.  
  7. While watching the rocker arms for the No. 1 cylinder, rotate the crankshaft until the exhaust valve is closing and the intake valve has just started to open. At this point, the No. 4 cylinder piston will be at Top Dead Center (TDC) on the power stroke.
  8.  

  1. Loosen the locknut on cylinder No. 4 intake valve adjusting screw 2 or more turns.
  2.  
  3. Loosen the locknut on the jet valve adjusting screw.
  4.  
  5. Turn the jet valve adjusting screw counterclockwise and insert a 0.006 in. (0.15mm) feeler gauge between the jet valve stem and the adjusting screw.
  6.  
  7. Tighten the adjusting screw until it touches the feeler gauge.
  8.  

Take care not to press on the valve while adjusting, because the jet valve spring is very weak. If the adjusting screw is tight, special care must be taken to avoid pressing down on the jet valve when adjusting the clearance or a false reading will result.

  1. Tighten the locknut securely, while holding the rocker arm adjusting screw with a screwdriver to prevent it from turning.
  2.  
  3. Make sure that a 0.006 in. (0.15mm) feeler gauge can be easily inserted between the jet valve and the rocker arm.
  4.  
  5. Adjust the No. 4 cylinder intake valve to 0.006 in. (0.15mm) and its exhaust valve to 0.010 in.(0.25mm). Tighten the adjusting screw locknuts and recheck each clearance.
  6.  
  7. While watching the rocker arms for the No. 2 cylinder, rotate the crankshaft until the exhaust valve is closing and the intake valve has just started to open. At this point, the No. 3 cylinder piston will be at Top Dead Center (TDC) on the power stroke. Adjust the lash on No. 3 cylinder jet valve, intake valve and exhaust valve as detailed in Steps 5 through 11-make sure that the valves are adjusted for cylinder No. 3, not cylinder No. 4.
  8.  
  9. While watching the rocker arms for the No. 3 cylinder, once again rotate the crankshaft until the exhaust valve is closing and the intake valve has just started to open. At this point, the No. 2 cylinder piston will be at Top Dead Center (TDC) on the power stroke. Adjust the lash on No. 2 cylinder jet valve, intake valve and exhaust valve as detailed in Steps 5 through 11-make sure that the valves are adjusted for cylinder No. 2, not cylinder No. 4.
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  11. And finally while watching the rocker arms for the No. 4 cylinder, rotate the crankshaft until the exhaust valve is closing and the intake valve has just started to open. At this point, the No. 1 cylinder piston will be at Top Dead Center (TDC) on the power stroke. Adjust the lash on No. 1 cylinder jet valve, intake valve and exhaust valve as detailed in Steps 5 through 11-make sure that the valves are adjusted for cylinder No. 1, not cylinder No. 4.
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  13. Replace the valve cover and all other components. Make sure to apply sealer to the top surface of the semi-circular packing. For more details on installing the rocker arm covers, refer to Engine & Engine Overhaul .
  14.  
  15. Run the engine and check for oil leaks at the valve cover.
  16.  

 
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