Jeep CJ/Scrambler 1971-1986 Repair Guide

Timing Chain or Gears and Tensioner

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REMOVAL & INSTALLATION



See Figures 1, 2, 3, 4, 5, 6, 8, 7 and 9

4-134 Engine
  1. Remove the timing gear cover.
  2.  
  3. Use a puller to remove both the crankshaft and the camshaft gear from the engine after removing all attaching nuts and bolts.
  4.  
  5. Remove the Woodruff keys.
  6.  

Installation is as follows:
  1. Install the Woodruff key in the longer of the two keyways on the front end of the crankshaft.
  2.  
  3. Install the crankshaft timing gear on the front end of the crankshaft with the timing mark facing away from the cylinder block.
  4.  
  5. Align the keyway in the gear with the Woodruff key and then drive or press the gear onto the crankshaft firmly against the thrust washer.
  6.  
  7. Turn the camshaft or the crankshaft as necessary so that the timing marks on the two gears will be together after the camshaft gear is installed.
  8.  
  9. Install the Woodruff key in the keyway on the front of the camshaft.
  10.  
  11. Start the large timing gear on the camshaft with the timing mark facing out.
  12.  

Do not drive the gear onto the camshaft as the camshaft may drive the plug out of the rear of the engine and cause an oil leak.

  1. Install the camshaft retaining screw and torque it to 30-40 ft. lbs. This will draw the gear onto the camshaft as the screw is tightened. Standard running tolerance between the timing gears is 0-0.002 in. (0.05mm).
  2.  
  3. Install the timing gears with the marks aligned as shown.
  4.  
  5. Set the intake valve clearance to 0.020 in. (0.5mm) on the #1 cylinder.
  6.  
  7. Rotate the crankshaft until the #1 cylinder intake valve is ready to open as indicated by the IO mark on the flywheel. The mark should be centered in the hole.
  8.  

Some models do not have an IO mark. TC and 5° are the only marks. On these engines, the intake valve opens at 9° BTC. To estimate valve opening, measure the distance between TC and 5° and measure about that distance further on.

4-150 Engine
  1. Remove the timing case cover.
  2.  
  3. Rotate the crankshaft so that the timing marks on the cam and crank sprockets align next to each other, as illustrated.
  4.  
  5. Remove the oil slinger from the crankshaft.
  6.  
  7. Remove the cam sprocket retaining bolt and remove the sprocket and chain. The crank sprocket may also be removed at this time. If the tensioner is to be removed, the oil pan must be removed. first.
  8.  

To install:
  1. Prior to installation, turn the tensioner lever to the unlock (down) position.
  2.  
  3. Pull the tensioner block toward the tensioner to compress the spring. Hold the block and turn the tensioner lever to the lock (up) position. The camshaft sprocket bolt should be torqued to 50 ft. lbs. on 1984-86 models
  4.  
  5. Install the sprockets and chain together, as a unit. Make sure the timing marks are aligned.
  6.  
  7. To verify that the timing chain is correctly installed:
    1. Turn the crankshaft to place the camshaft timing mark at approximately the one o'clock position.
    2.  
    3. At this point, there should be a tooth on the crankshaft sprocket meshed with the chain at the three o'clock position.
    4.  
    5. Count the number of timing chain pins between the two timing marks on the right side (your right, facing the engine). There should be 20 pins.
    6.  

  8.  
  9. Install the oil pan, slinger and timing cover.
  10.  



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Fig. Fig. 1: Valve timing mark alignment on the 4-150 engine



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Fig. Fig. 2: Timing chain tensioner used on the 4-150 engine. Note that No. 1 is the tensioner lever and No. 2 is the tensioner block

4-151 Engine

Removal of the camshaft gear requires a special adapter #J-971 and the use of a press. Camshaft removal is necessary.

  1. Place the adapter on the press and place the camshaft through the opening.
  2.  
  3. Press the shaft out of the gear using a socket or other suitable tool.
  4.  


WARNING
The thrust plate must be in position so that the woodruff key does not damage the gear when the shaft is pressed out.

  1. To install the gear firmly support the shaft at the back of the front journal in an arbor press using pressplate adapters J-21474-13 or J-21795-1.
  2.  
  3. Place the gear spacer ring and thrust plate over the end of the shaft, and install the woodruff key in the shaft keyway.
  4.  
  5. Install the camshaft gear and press it onto the shaft until it bottoms against the gear spacer ring. The end clearance of the thrust plate should be 0.0015-0.0050 in. (0.038-0.13mm). If less than 0.0015 in. (0.038mm), the spacer ring should be replaced.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: Installing the camshaft timing gear on the 4-151 engine and measuring thrust plate end clearance



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Fig. Fig. 4: Timing mark alignment on the 4-151 engine

6-225 Engine
  1. Remove the timing chain cover.
  2.  
  3. Make sure that the timing marks on the crankshaft and the camshaft sprockets are aligned. This will make installing the parts easier.
  4.  

It is not necessary to remove the timing chain dampers (tensioners) unless they are worn or damaged and require replacement.

  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. Remove the eccentric and the gear from the camshaft.
  4.  
  5. Alternately pry forward the camshaft sprocket and then the crankshaft sprocket until the camshaft sprocket is pried from the camshaft.
  6.  
  7. Remove the camshaft sprocket, sprocket key, and timing chain from the engine.
  8.  
  9. Pry the crankshaft sprocket from the crankshaft.
  10.  

Install as follows:
  1. If the engine has not been disturbed proceed to step Number 4 for installation procedures.
  2.  
  3. If the engine has been disturbed turn the crankshaft so that number one piston is at top dead center.
  4.  
  5. Temporarily install the sprocket key and the camshaft sprocket on the camshaft. Turn the camshaft so that the index mark of the sprocket is downward. Remove the key and sprocket from the camshaft.
  6.  
  7. Assemble the timing chain and sprockets. Install the keys, sprockets, and chain assembly on the camshaft and crankshaft so that the index marks of both the sprockets are aligned.
  8.  

It will be necessary to hold the spring loaded timing chain damper out of the way while installing the timing chain and sprocket assembly.

  1. Install the front oil slinger on the crankshaft with the inside diameter against the sprocket (concave side toward the front of the engine).
  2.  
  3. Install the fuel pump eccentric on the camshaft and the key, with the oil groove of the eccentric forward.
  4.  
  5. Install the distributor drive gear on the camshaft. Secure the gear and eccentric to the camshaft with the retaining washer and bolt.
  6.  
  7. Torque the bolt to 40-55 ft. lbs.
  8.  

6-232 and 6-258 Engine
  1. Remove the drive belts, engine fan and hub assembly, accessory pulley, vibration damper and timing chain cover.
  2.  
  3. Remove the oil seal from the timing chain cover.
  4.  
  5. Remove the camshaft sprocket retaining bolt and washer.
  6.  
  7. Rotate the crankshaft until the timing mark on the crankshaft sprocket is closest to and in a center line with the timing pointer of the camshaft sprocket.
  8.  
  9. Remove the crankshaft sprocket, camshaft sprocket and timing chain as an assembly. Disassemble the chain and sprockets.
  10.  

Installation is as follows:
  1. Assemble the timing chain, crankshaft sprocket and camshaft sprocket with the timing marks aligned.
  2.  
  3. Install the assembly to the crankshaft and the camshaft.
  4.  
  5. Install the camshaft sprocket retaining bolt and washer and tighten to 45-55 ft. lbs.
  6.  
  7. Install the timing chain cover and a new oil seal.
  8.  
  9. Install the vibration damper, accessory pulley, engine fan and hub assembly and drive belts. Tighten the belts to the proper tension.
  10.  



Click image to see an enlarged view

Fig. Fig. 5: Timing mark alignment on the 6-232 and 6-258 engines



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Fig. Fig. 6: Timing mark alignment verification on the 6-232 and 6-258 engines

8-304 Engine
  1. Remove the timing chain cover and gasket.
  2.  
  3. Remove the crankshaft oil slinger.
  4.  
  5. Remove the camshaft sprocket retaining bolt. and washer, distributor drive gear and fuel pump eccentric.
  6.  
  7. Rotate the crankshaft until the timing mark on the crankshaft sprocket is adjacent to, and on a center line with, the timing mark on the camshaft sprocket.
  8.  
  9. Remove the crankshaft sprocket, camshaft sprocket and timing chain as an assembly.
  10.  
  11. Clean all of the gasket surfaces.
  12.  

Installation is as follows:
  1. Assemble the timing chain, crankshaft sprocket and camshaft sprocket with the timing marks aligned as illustrated. The timing mark on the camshaft sprocket should be on a horizontal line at the 3 o'clock position, while the mark on the crankshaft sprocket should be on a vertical line at the 6 o'clock position.
  2.  
  3. Install the assembly to the crankshaft and the camshaft. You may have to turn the shafts to properly align the keyways.
  4.  
  5. Install the fuel pump eccentric, distributor drive gear, washer and retaining bolt. Tighten the bolt to 25-35 ft. lbs.
  6.  
  7. Count the number of timing chain pins between the camshaft and crankshaft sprockets. Start counting with the pin directly adjacent to the timing mark on the camshaft sprocket and continue downwards to the mark on the crankshaft sprocket. There must be 20 pins between these 2 points (the mark on the crankshaft sprocket must be between pins 20 and 21) or timing will be incorrect. Rotate the crankshaft in order to turn the marks through until they align on the vertical centerline at the point closest together (camshaft mark at 6 o'clock and crankshaft mark at 12 o'clock). If the marks do not align properly, the timing chain and sprockets must be removed and repositioned.
  8.  
  9. Install the crankshaft oil slinger.
  10.  
  11. Install the timing chain cover using a new gasket and oil seal.
  12.  

In mid-year 1979, a new timing chain, camshaft sprocket and crankshaft sprocket were phased into production on all 8-304 engines. These are offered as replacement parts for older engines. When installing any one of these parts on an older engine, all three parts must be installed. None of the new parts is usable in conjunction with the older parts. They must be installed as a set. To determine the necessity for a replacement of an older chain, perform the following deflection test:

  1. Remove the timing case cover.
  2.  
  3. Rotate the sprockets until all slack is removed from the right side of the chain.
  4.  
  5. Locate the dowel on the lower left side of the engine and measure up 3 / 4 in. (19mm). Make a mark.
  6.  
  7. Measure across the chain with a straightedge from the mark to a point at the bottom of the camshaft sprocket.
  8.  
  9. Grab the chain at the point where the straightedge crosses it. Push the chain left (inward) as far as it will go. Make a mark on the block at this point. Push the chain to the right as far as it will go. Make another mark. Measure between the two marks. Total deflection should not exceed 7 / 8 in. (22mm).
  10.  
  11. Replace the chain and sprockets if deflection is not within specifications.
  12.  
  13. Replace the timing case cover.
  14.  



Click image to see an enlarged view

Fig. Fig. 7: Correct timing chain installation verification on the 8-304 engine



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Fig. Fig. 8: Turn the crankshaft in order to rotate the timing marks to align on the centerline-8-304 engine



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Fig. Fig. 9: Measuring timing chain deflection on the 8-304 engine

 
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