Chevrolet Blazer/Jimmy 1969-1982 Repair Guide

Timing Chain/Gears

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REMOVAL & INSTALLATION



Six Cylinder Engines


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Fig. Fig. 1 Timing gear alignment-6 cylinder engine



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Fig. Fig. 2 1. Timing chain 2. Camshaft sprocket 3. Crankshaft sprocket Typical timing chain and gears used on V8 engines



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Fig. Fig. 3 To remove the timing chain and gears, align the gears dot-to-dot, then unfasten the camshaft timing gear bolts ...



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Fig. Fig. 4 ... then remove the camshaft gear and chain together



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Fig. Fig. 5 If necessary, use a gear puller to loosen the crankshaft gear ...



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Fig. Fig. 6 ... then remove the crankshaft gear from the engine



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Fig. Fig. 7 Make sure when the gears are installed that the timing marks on the gears align

The six cylinder camshaft is gear driven.

  1. To remove the camshaft gear, remove the camshaft and press the gear off.
  2.  
  3. The crankshaft gear may be removed with a gear puller while in place in the block.
  4.  

V8 Engines

V8 models are equipped with a timing chain.

  1. To replace the chain, remove the radiator core, water pump harmonic balancer, and the crankcase front cover.
  2.  
  3. This will allow access to the timing chain.
  4.  
  5. Crank the engine until the timing marks punched on both sprockets are closest to one another and in line between the shaft centers.
  6.  
  7. Take out the three bolts that hold the camshaft sprockets to the camshaft. This is a light press fit on the camshaft and will come off readily. It is located by a dowel.
  8.  
  9. The chain comes off with the camshaft sprocket.
  10.  

A gear puller will be required to remove the crankshaft sprocket.

To install:

  1. Without disturbing the position of the engine, mount the new crankshaft sprocket on the shaft, then mount the chain over the camshaft sprocket.
  2.  
  3. Arrange the camshaft sprocket in such a way that the timing marks will line up between the shaft centers and the camshaft locating dowel will enter the dowel hole in the cam sprocket.
  4.  
  5. Place the cam sprocket, with its chain mounted over it, in position on the front of the camshaft and pull up with the three bolts that hold it to the camshaft.
  6.  
  7. After the chain and sprocket are in place, turn the engine two full revolutions to make certain that the timing marks are in correct alignment between the shaft centers.
  8.  

Diesel Engines


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Fig. Fig. 8 Timing sprocket alignment-V8 engine

  1. Remove the front cover.
  2.  
  3. Remove the bolt and washer attaching the camshaft gear to the camshaft sprocket.
  4.  
  5. Remove the injection pump gear.
  6.  
  7. Slide the cam sprocket and timing chain off the shaft and then remove the crankshaft sprocket.
  8.  

To install:

  1. Install the crank sprocket, the cam sprocket and the timing chain together. Make sure the timing marks on the sprockets are aligned.
  2.  
  3. Rotate the crankshaft 360° so that the camshaft gear and the injection pump gear are aligned.
  4.  
  5. Install the front cover. Anytime the timing chain, gear or sprockets are removed it will be necessary to retime the engine.
  6.  

 
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