GM Firebird 1967-1981 Repair Guide

Timing Belt and Front Crankcase Cover

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REMOVAL & INSTALLATION OHC 230 and 250 Engines



See Figure 1

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Fig. Fig. 1: Timing mark alignment for timing belt removal on 1967-68 OHC 230 and 250 engines

See Figure 2

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Fig. Fig. 2: Align the timing marks as shown before removing the timing belt from 1969 OHC 250 engines

TIMING BELT

Radiator removal, at this point, is a distinct advantage for this operation.


CAUTION
When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Remove the upper front timing cover.
  2.  
  3. Align the timing marks.
  4.  

There are three sets of timing marks that must be aligned. One set is located on the harmonic balancer and the lower front belt cover. A second set is located on the accessory drive housing pulley and the lower front belt cover. The third set is the camshaft pulley set.

The mark on the harmonic balancer must be aligned with zero (0ordm;) on the cover with the No. 1 cylinder on TDC of the compression stroke. The mark on the drive pulley should point toward the water pump and align with its mark on the belt cover. The mark on the camshaft pulley, on 1967-68 models, aligns with a mark on the cover behind the pulley. In 1969, the camshaft pulley mark aligns with a mark on a bolt head located directly below the camshaft pulley.

All three sets of marks must be aligned at the same time when replacing the timing belt.

  1. Remove the fan and water pump pulley.
  2.  
  3. Remove the harmonic balancer.
  4.  
  5. Remove the timing belt lower front cover.
  6.  
  7. Loosen the accessory drive mounting bolts to provide slack in the timing belt.
  8.  
  9. Remove the timing belt.
  10.  
  11. Remove the crankshaft timing belt flange and sprocket.
  12.  
  13. Carefully remove the seal from the crankcase cover.
  14.  

To install:
  1. Install a new seal, with the lip of the seal inward.
  2.  
  3. Install the crankshaft timing belt sprocket and flange.
  4.  
  5. Align the timing marks, if no longer aligned, then install the timing belt.
  6.  
  7. Replace the timing belt lower cover and harmonic balancer.
  8.  
  9. Adjust the timing belt tension.
  10.  
  11. Replace the water pump pulley and fan.
  12.  
  13. Replace the timing belt upper front cover.
  14.  

FRONT CRANKCASE COVER
  1. Remove the timing belt sprocket, as described earlier in this section.
  2.  
  3. Remove the 4 front oil pan-to-crankcase cover retaining bolts.
  4.  
  5. Loosen the remaining oil pan bolts, as necessary, to provide clearance between the crankcase cover and oil pan.
  6.  
  7. Remove the 5 front crankcase cover attaching bolts.
  8.  
  9. Remove the front crankcase cover and gasket, clean off the old gasket.
  10.  
  11. Inspect the cover seal for wear or distortion.
  12.  
  13. Using a new gasket installed over the dowels and, as necessary, a new seal, reverse the removal procedures, tighten the oil pan and crankcase cover bolts to 10-15 ft. lbs.
  14.  

TIMING BELT ADJUSTMENTOHC 230 and 250 Engines



Pontiac special tools, Nos. J-22232-1 and J-22232-2, or commercial substitutes, are necessary for this adjustment.

  1. Remove the timing belt top front cover.
  2.  
  3. Using the J-22232-2 calibration bar, set the pointer of the timing belt tension fixture J-22232-1 to zero.
  4.  

This calibration must be performed before each use of J-22232 fixture to insure an accurate timing belt adjustment.

  1. Remove the camshaft sprocket-to-camshaft bolt and install J-22232-1 (tension fixture) on the belt with the roller on the outside (smooth) surface of the belt. Thread the fixture mounting bolt into the camshaft sprocket bolt location finger-tight.
  2.  
  3. Squeeze the indicator end (upper) of the fixture and quickly release it so that the fixture assumes a released or relaxed position.
  4.  
  5. With J-22232-1 installed adjust the accessory drive housing up or down, as required, to obtain a tension adjustment indicator reading centered in the green range, with the drive housing mounting bolts tightened to 7-13 ft. lbs.
  6.  
  7. Remove the tension fixture and install the sprocket retaining bolt, making sure that the bolt threads and washers are free of dirt.
  8.  

 
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