Toyota Cressida/Corona/Crown/MarkII 1970-1982 Repair Guide

Valve Lash

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Toyota models equipped with mechanical valve lifters should be adjusted at the factory recommended intervals (every 12,000 miles, 15,000 miles for late models).

Valve adjustment is one factor which determines how far the intake and exhaust valves will open into the cylinder.

If the valve clearance is too large, part of the lift of the camshaft will be used up in removing the excessive clearance, thus the valves will not be opened far enough. This condition has two effects, the valve train components will emit a tapping noise as they take up the excessive clearance, and the engine will perform poorly, since the less the intake valves open, the smaller the amount of air/fuel mixture that will be admitted to the cylinders. The less the exhaust valves open, the greater the back-pressure in the cylinder which prevents the proper air/fuel mixture from entering the cylinder.

If the valve clearance is too small, the intake and exhaust valves will not fully seat on the cylinder head when they close. When a valve seats on the cylinder head it does two things. It seals the combustion chamber so none of the gases in the cylinder can escape and it cools itself by transferring some of the heat it absorbed from the combustion process through the cylinder head and into the engine cooling system. Therefore, if the valve clearance is too small, the engine will run poorly (due to gases escaping from the combustion chamber), and the valves will overheat and warp (since they cannot transfer heat unless they are touching the seat in the cylinder head).

While all valve adjustments must be as accurate as possible, it is better to have the valve adjustment slightly loose than slightly tight, as burnt valves may result form overly tight adjustments.

ADJUSTMENT
8R-C and 18R-C Engines


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Fig. Fig. 1 Valve arrangement for the 8R-C and 18R-C engines



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Fig. Fig. 2 Valve adjusting sequence-8R-C and 18R-C engines



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Fig. Fig. 3 Measure the clearance between the valve stem and adjusting nut; there should be a slight drag on the feeler gauge when properly installed

  1. Start the engine and allow it to reach normal operating temperature (above 175°F).
  2.  
  3. Stop the engine. Remove the air cleaner assembly, its hoses, and bracket. Remove any other cables, hoses, wires, etc., which are attached to the valve cover. Remove the valve cover. Be careful, some metal parts get quite hot.
  4.  
  5. Check the torque of the valve rocker shaft bolts and the camshaft bearing bolts. They should be 12-17 ft. lbs.
  6.  
  7. Check the torque specification of the camshaft bearing cap union bolts. They should be torqued to 11-16 ft. lbs.
  8.  
  9. Set the No. 1 cylinder to TDC on its compression stroke. Disconnect the high tension lead from the coil. Remove the spark plug from the No. 1 cylinder and place a screwdriver handle over the hole. Crank the engine until a pressure is felt, then line the V-notch on the crankshaft pulley with the pointer on the timing chain cover. The No. 1 cylinder is now at TDC.
  10.  


CAUTION
Do not cover the spark plug hole with your finger when determining the compression stoke. The cylinder head is hot and a burn could occur.

Do not start the engine. Valve clearances are checked with the engine stopped to prevent hot oil from being splashed out by the timing chain.

  1. Check the clearances (see the Tune-Up Specifications chart) and adjust valves 1, 2, 3, and 5 to the proper specifications, if necessary.
  2.  
  3. To adjust the valve clearance, loosen the locknut and turn the adjusting screw until the specified clearance is obtained. Tighten the locknut and check the clearance again.
  4.  
  5. Crank the engine one revolution (360 degress) and perform Steps 6 and 7 for valves 4, 6, 7, and 8.
  6.  
  7. Install the spark plug in the No. 1 cylinder. Connect the high tension lead to the coil. Install the valve cover, air cleaner assembly, and any other components which were removed.
  8.  

20R and 22R Engines


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Fig. Fig. 4 Disconnect and plug the hot air intake and mixture control hoses before adjusting the valves-20R and 22R engines



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Fig. Fig. 5 Valve arrangement-20R and 22R engines



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Fig. Fig. 6 Adjust this set of valves first-20R and 22R engines

  1. Start the engine and allow it to reach normal operating temperature (above 180°F).
  2.  
  3. Stop the engine. Remove the air cleaner assembly, its hoses, and bracket. Remove any other cables, hoses, wires, etc., which are attached to the valve cover. Remove the valve cover.
  4.  
  5. Set the No. 1 cylinder at top dead center (TDC) of its compression stroke. Remove the high tension lead from the coil. Remove the spark plug from the No. 1 cylinder and place a screwdriver handle over the hole. Crank the engine until pressure is felt and the TDC notch is lined up with the pointer. The No. 1 cylinder is now at TDC.
  6.  


CAUTION
Do not cover the spark plug hole with your finger when determining the compression stroke. The cylinder head is hot and a burn could occur.

  1. Measure the clearance between the valve stem and the rocker arm with a feeler gauge for the valves marked FIRST in the illustration. See the Tune-Up Specifications chart for the correct clearance.
  2.  
  3. To adjust the valve clearance, loosen the locknut and turn the adjusting screw until the proper clearance is obtained. Tighten the locknut and check the clearance again.
  4.  
  5. Crank the engine one revolution (360°) and perform Steps 4 and 5 for the set of valves marked SECOND in the illustration.
  6.  
  7. Install the spark plug in the No. 1 cylinder and reconnect the coil lead. Install the valve cover, air cleaner, assembly, and any other components which were removed.
  8.  

M Series Engines


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Fig. Fig. 7 Turn the crankshaft 360 degrees, then adjust this set of valves-M series engines



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Fig. Fig. 8 When adjusting the valves, turn the crankshaft to align the timing marks to TDC of the compression stroke with the pulley in the 0 position



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Fig. Fig. 9 Valve arrangement for the 4M-E and 5M-E engines



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Fig. Fig. 10 Adjust this set of valves first-M series engines



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Fig. Fig. 11 Using a feeler gauge, measure between the valve stem and the rocker arm, loosen the locknut, then turn the screw to set the clearance



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Fig. Fig. 12 Turn the crankshaft 360 degrees, then adjust this set of valves-M series engines

  1. Allow the engine to reach normal operating temperature. Stop the engine.
  2.  
  3. Remove the air cleaner assembly, air cleaner bracket, spark plug cable guides, and any other components attached to the valve cover. Remove the valve cover. Be careful, some metal parts get very hot.
  4.  
  5. Disconnect the high tension lead from the coil. Crank the engine until the No. 1 cylinder is at TDC of its compression stroke. To determine this, remove the spark plug from the No. 1 cylinder and place a screwdriver handle over the spark plug hole. Crank the engine until pressure is felt against the screwdriver handle and the slot in the crankshaft pulley aligns with the 0 (TDC) on the timing scale.
  6.  


CAUTION
Do not cover the spark plug hole with your finger when determining the compression stroke, as the nearness of the hole to the exhaust manifold could result in a severe burn.

  1. Check and adjust the clearance of the intake valve on 1, 2, and 4 cylinders and of the exhaust valves on 1, 3, and 5 cylinders.
  2.  
  3. Measure the clearance between the valve stem and the adjusting screw with a feeler gauge of the proper size. (See the Tune-Up Specifications chart at the beginning of this section.).
  4.  
  5. If the valves require adjustment, loosen the locknut and turn the adjusting screw until the proper clearance is obtained. Tighten the locknut. Check the clearance again.
  6.  
  7. Crank the engine one revolution (360°) and repeat Steps 5 and 6 for the remaining valves.
  8.  
  9. Install the cylinder head cover, spark plug cable guides, air cleaner bracket, air cleaner assembly and any other components which were removed. Replace the No. 1 spark plug and reconnect the coil high tension lead, as well.
  10.  

 
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