GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Timing Chain

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REMOVAL & INSTALLATION



See Figures 1, 2, 3, 4, 5, 6 and 7

231 V6
  1. Remove the timing chain cover. For details, refer to the procedure earlier in this section.
  2.  
  3. Before removing anything else, make sure the timing marks on the crankshaft and camshaft sprockets are aligned. This will greatly ease reinstallation of parts.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of a common timing cover, gear and chain assembly

It is not necessary to remove the timing chain tensioners unless they are worn or damaged.

  1. Remove the front crankshaft oil slinger.
  2.  
  3. Remove the bolt and the special washer that hold the camshaft distributor drive gear and fuel pump eccentric at the forward end of the camshaft.
  4.  
  5. Using a pair of prybars, alternately pry the camshaft sprocket, then the crankshaft sprocket forward until the camshaft sprocket is free. Be careful not to damage the sprockets or the ends of the shafts.
  6.  
  7. Remove the camshaft sprocket along with the chain, then finish pulling the crankshaft sprocket off the shaft.
  8.  

To install:
  1. If the engine has been disturbed, turn the the crankshaft so that the number one piston is at top dead center. With the crankshaft turned to No. 1 TDC, temporarily install the sprocket key and the camshaft sprocket on the camshaft, then turn the camshaft so that the index mark of the sprocket is pointing downward. Remove the key and the sprocket from the camshaft.
  2.  
  3. Make sure the sprocket keys are properly installed. Arrange the sprockets in the timing chain so the marks are aligned at the point closest together. Slide the sprocket and chain assembly on both the crankshaft and camshaft at the same time, making sure the marks remain aligned. An assistant may be helpful as it will be necessary to hold the chain tensioners out of the way while installing the timing chain and sprocket assembly.
  4.  
  5. Install the front oil slinger on the crankshaft with the concave side toward the front of the engine.
  6.  
  7. Install the fuel pump eccentric with the oil groove forward.
  8.  
  9. Install the distributor drive gear on the camshaft.
  10.  
  11. Install the front cover.
  12.  



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Fig. Fig. 2: Remove the timing cover from the engine for access to the timing chain and gears



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Fig. Fig. 3: Before removal, make sure the timing marks are aligned at their closest point of rotation



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Fig. Fig. 4: Remove the camshaft sprocket and timing chain assembly

V6 and V8 Gasoline Engines (Except 231 V6)
  1. Remove the timing chain cover. For details, refer to the procedure earlier in this section.
  2.  
  3. Turn the crankshaft until the mark on the camshaft sprocket aligns with the mark on the crankshaft sprocket.
  4.  
  5. Remove the camshaft sprocket bolts, then remove the camshaft sprocket and timing chain assembly. If necessary, remove the crankshaft sprocket with or after the assembly.
  6.  

When installing the timing chain, install the sprockets with the timing marks facing each other; this position is TDC of the No. 6 cyl. (V8) or No. 4 cyl. (V6). To locate the TDC of the No. 1 cylinder, turn the crankshaft one full revolution, the camshaft timing mark will now be at the top of the sprocket.

To install:
  1. If removed, install the crankshaft sprocket. Make sure the timing mark is at the top of the sprocket so the pistons are properly positioned to set engine timing.
  2.  
  3. Insert the camshaft timing sprocket into the timing chain so the mark on the sprocket is facing downward.
  4.  
  5. Install the bottom of the chain under the crankshaft sprocket as you install the camshaft sprocket to the end of the shaft. Make sure the sprockets are properly installed and seated, then make sure the timing marks are properly aligned.
  6.  
  7. Install and tighten the camshaft sprocket retaining bolts to 13-23 ft. lbs. (18-31 Nm).
  8.  
  9. Install the timing chain cover.
  10.  



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Fig. Fig. 5: Timing mark alignment during removal and installation of the chain assembly-all V-type engines



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Fig. Fig. 6: On 1980 and later gasoline engines (except the 231 V6) and all V8 diesel engines, camshaft timing mark alignment results in these engine timing positions

350 V8 Diesel
  1. Remove the timing chain cover. For details, refer to the procedure earlier in this section.
  2.  
  3. Align the timing marks for ease of installation.
  4.  
  5. Remove the oil slinger and camshaft bolts, then remove the camshaft and crankshaft sprockets along with the timing chain as an assembly.
  6.  
  7. If replacement is necessary, remove the fuel pump eccentric from the crankshaft.
  8.  

To install:
  1. If removed, install the key in the crankshaft and/or the fuel pump eccentric.
  2.  
  3. Position the sprockets in the timing chain with the timing marks aligned. Install the camshaft and crankshaft sprockets along with the timing chain as an assembly.
  4.  
  5. Make sure the timing marks are still in alignment, then install and tighten the camshaft sprocket bolt to 65 ft. lbs. (88 Nm).
  6.  

When the two timing marks are in alignment at the point they are closest together, the number six cylinder is at TDC. To obtain TDC for number one cylinder, slowly rotate the crankshaft one revolution. This will bring the camshaft sprocket mark to the top and the number one piston will then be in firing position.

  1. Install the oil slinger.
  2.  
  3. Install the timing chain front cover.
  4.  

Any time the timing chain and gears are replaced, it will be necessary to retime the injection system. Refer to diesel engine injection timing in Fuel System of this information.



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Fig. Fig. 7: Exploded view of the timing cover and chain assembly (along with bolt torques)-263 V6 diesel engine

263 V6 Diesel
  1. Remove the timing chain cover. For details, refer to the procedure earlier in this section.
  2.  
  3. Remove the rocker arm covers and loosen all of the rocker arm pivot bolts evenly so that lash exists between the rocker arms and the valves (the pushrods and rocker arms are loose). It is not necessary to remove the rockers completely.
  4.  
  5. Align the timing marks for ease of installation.
  6.  
  7. Remove the crankshaft oil slinger.
  8.  
  9. Remove the camshaft-to-camshaft sprocket bolt and washer, then remove the timing chain, camshaft and crankshaft sprockets as an assembly.
  10.  

If the crank sprocket is a tight fit on the end of the crankshaft, you may have to use a sprocket puller to remove it.

To install:
  1. If the camshaft sprocket key should come out with the camshaft sprocket, perform the following by referring to the exploded drawing of the V6 diesel front cover and timing assembly.
    1. Remove the front camshaft bearing retainer.
    2.  
    3. Install the key with the injection pump drive gear.
    4.  
    5. Install the bearing retainer and bolts loose on the block.
    6.  
    7. Install the camshaft sprocket.
    8.  
    9. Rotate the camshaft at least 4 turns to center the retainer.
    10.  
    11. Remove the camshaft sprocket.
    12.  
    13. Torque the bearing retainer-to-block bolts evenly to 48 ft. lbs. (65 Nm).
    14.  
    15. Rotate the camshaft to make sure it's free. If it is not, repeat steps a-h.
    16.  

  2.  
  3. If removed, install the key in the crankshaft.
  4.  
  5. Position the camshaft and crankshaft sprockets into the timing chain with the timing marks aligned. Install the camshaft and crankshaft sprockets along with the timing chain as an assembly
  6.  
  7. Make sure the timing marks are still aligned, then install and tighten the camshaft sprocket bolt to 70 ft. lbs. (95 Nm).
  8.  
  9. Install the oil slinger.
  10.  
  11. Install the engine timing chain front cover.
  12.  
  13. Bleed-down the valve lifters as described under rocker arm service earlier in this section.
  14.  
  15. Install the valve covers and check and reset the injection pump timing.
  16.  

 
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