GM Firebird 1967-1981 Repair Guide

Camshaft

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REMOVAL & INSTALLATION OHC 230 and 250 Engines



  1. Remove the camshaft sprocket and seal.
  2.  
  3. Remove the rocker cover assembly.
  4.  
  5. Using an adapter (Pontiac special tool No. J-22284 or a substitute) and a slide hammer, drive the camshaft to the rear. Be careful that the bearing surfaces are not damaged during this operation.
  6.  
  7. Disconnect the slide hammer and remove the camshaft from the rear of the rocker cover.
  8.  
  9. Remove the thrust washer, retaining washer, and bolt from the rear of the camshaft.
  10.  
  11. Clean and inspect all parts for wear or damage, then inspect the bearing surfaces for wear or scoring.
  12.  
  13. Clean the camshaft oil passages.
  14.  

To install:
  1. Reverse the removal procedure making sure that the thrust washer is installed as illustrated. Tighten the retaining bolt to 40 ft. lbs.
  2.  
  3. Check the camshaft end-play, using a dial indicator on the front sprocket; end-play should be 0.003-0.009 in. and is controlled by the camshaft bore plug.
  4.  

Lubricate the camshaft lobes and rockers with special break-in lubricant or gear oil. Tighten the locker cover bolts and nuts to 15 ft. lbs. from the center outward.

OHV 230 and 250 Engines See Figure 1

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Fig. Fig. 1: The timing marks on the crankshaft and camshaft gears should be positioned as indicated prior to gear or camshaft removal OHV 250 engines

Due to the length of the inline 6-cylinder camshaft, a large amount of working room will be required in front of the engine to remove the camshaft. There are two ways to go about this task: either remove the engine from the car, or remove the radiator, grille and all supports which are mounted directly in front of the engine. If the second alternative is chosen, you must also disconnect the motor mounts and raise the front of the engine enough to gain the clearance necessary to remove the cam from the engine.


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. In addition to removing the timing gear cover, remove the grille and radiator.
  2.  
  3. Remove the valve cover and gasket, loosen all the valve rocker arm nuts and pivot the arms clear of the pushrods.
  4.  
  5. Remove the distributor and the fuel pump.
  6.  
  7. Remove the coil, the side cover and the gasket. Remove the pushrods and valve lifters.
  8.  
  9. Remove the two camshaft thrust plate retaining screws by working through the holes in the camshaft gear.
  10.  
  11. Remove the camshaft and gear assembly by pulling it out through the front of the block.
  12.  

If renewing either the camshaft or camshaft gear, the gear must be pressed off the camshaft. The replacement parts must be assembled in the same manner (under pressure). In placing the gear on the camshaft, press the gear onto the shaft until it bottoms against the gear spacer ring. The end clearance of the thrust plate should be 0.001-0.005 in.

  1. Install the camshaft assembly in the engine.
  2.  

Pre-lube the cam lobes with E.O.S. or SAE 90 gear lubricant. Do not dislodge the cam bearings when inserting the camshaft.

  1. Turn the crankshaft and the camshaft to align and bring the timing marks together. Push the camshaft into this aligned position. Install the camshaft thrust plate-to-block screws and tighten them to 6-7 1 / 2 lbs.
  2.  
  3. Run-out on either the crankshaft or the camshaft gear should not exceed .003 in.
  4.  
  5. Backlash between the two gears should be between 0.004 and 0.006 in.
  6.  
  7. Install the timing gear cover and its gasket.
  8.  
  9. Install the oil pan and gaskets.
  10.  
  11. Install the harmonic balancer.
  12.  
  13. Line up the keyway in the balancer with the key on the crankshaft and the drive balancer onto the shaft until it bottoms against the crankshaft gear.
  14.  
  15. Install the valve lifters and pushrods. Install the side cover with a new gasket. Attach the coil wires; then install the fuel pump.
  16.  
  17. Install the distributor and set the timing as described under Distributor Installation at the beginning of this section.
  18.  
  19. Pivot the rocker arms over the pushrods and adjust the valves.
  20.  
  21. Add oil to the engine. Install and adjust the fan belt.
  22.  
  23. Install the radiator or shroud.
  24.  
  25. Install the grille assembly.
  26.  
  27. Fill the cooling system, start the engine and check for leaks.
  28.  
  29. Check and adjust the timing.
  30.  

231 Engine


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. Drain the engine coolant and remove the radiator and radiator hoses.
  2.  
  3. Remove the water pump and all the drive belts. Remove the alternator.
  4.  
  5. Remove the crankshaft pulley and the vibration damper.
  6.  
  7. Remove the intake manifold. Mark the location of the distributor and remove the distributor.
  8.  
  9. Remove the fuel pump. Remove the timing chain cover and the oil pump.
  10.  
  11. Remove the timing chain and the camshaft sprocket, along with the distributor drive gear and the fuel pump eccentric.
  12.  
  13. Remove the rocker arm covers and the rocker arm assemblies. Mark the pushrods and remove them. Remove the lifters. Mark them so they can be returned to their original position.
  14.  
  15. Carefully remove the camshaft from the engine. Make sure you don't damage the bearings.
  16.  
  17. Installation is in the reverse order of removal. Remember to pack the oil pump with petroleum jelly.
  18.  

265, 301, 305, 326, 350, 400, 403 and 455 Engines


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. Drain the cooling system and remove the air cleaner.
  2.  
  3. Disconnect all water hoses, vacuum lines, and spark plug wires. Remove the radiator.
  4.  
  5. Disconnect the accelerator linkage, temperature gauge wire, and fuel lines.
  6.  
  7. Remove the hood latch brace.
  8.  
  9. Remove the PCV hose, then remove the rocker covers.
  10.  

On air-conditioned models, remove the alternator and its bracket.


CAUTION
Please refer to Repair Guide before discharging the compressor or disconnecting air conditioning lines. Damage to the air conditioning system or personal injury could result. Consult your local laws concerning refrigerant discharge and recycling. In many areas it may be illegal for anyone but a certified technician to service the A/C system. Always use an approved recovery station when discharging the air conditioning.

  1. Remove the distributor, then remove the intake manifold.
  2.  
  3. Remove the valley cover.
  4.  
  5. Loosen the rocker arm nuts and pivot the rockers out of the way.
  6.  
  7. Remove the pushrods and lifters, keeping them in proper order.
  8.  
  9. Remove the harmonic balancer, fuel pump, and 4 oil pan-to-timing cover bolts.
  10.  
  11. Remove the timing cover and gasket, then remove the fuel pump eccentric and the bushing.
  12.  
  13. Align the timing marks, then remove the timing chain and sprockets.
  14.  
  15. Remove the camshaft thrust plate.
  16.  
  17. Remove the camshaft by pulling it straight forward, being careful not to damage the cam bearings in the process.
  18.  

All camshaft journals are the same diameter and care must be taken while removing the camshaft to avoid damage to the bearings.

  1. Install the new camshaft (with the lobes and journals coated with heavy SAE 50-60 oil) into the engine, being careful not to damage the cam bearings.
  2.  
  3. Install the camshaft thrust plate and tighten the bolts to 20 ft. lbs.
  4.  

Before installing the timing cover, make sure that the No. 1 piston is at TDC of its compression stroke and that the timing marks are correctly aligned for your engine.

  1. Installation is in the reverse order of removal.
  2.  

 
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