REMOVAL & INSTALLATION
All Gasoline Engines
- Before beginning any disassembly procedures, position the No. 1 piston at TDC on the compression stroke.
- Remove the front cover as previously outlined. Remove the camshaft cover and remove the fuel pump if it runs off a cam lobe in front of the camshaft sprocket.
- With the No. 1 piston at TDC, the timing marks in the camshaft sprocket and the timing chain should be visible. Mark both of them with paint. Also mark the relationship of the camshaft sprocket to the camshaft. At this point you will notice that there are three sets of timing marks and locating holes in the sprocket. They are for making adjustments to compensate for timing chain stretch. See the Timing Chain Adjustment for more details.
- With the timing marks on the cam sprocket clearly marked, locate and mark the timing marks on the crankshaft sprocket. Also mark the chain timing mark. Of course, if the chain is not to be re-used, marking it is useless.
- Unbolt the camshaft sprocket and remove the sprocket along with the chain. As you remove the chain, hold it where the chain tensioner contacts it. When the chain is removed, the tensioner is going to come apart. Hold on to it and you won't lose any of the parts. There is no need to remove the chain guide unless it is being replaced.
- Using a suitable gear puller, remove the crankshaft sprocket assembly.
- Install the timing chain and the camshaft sprocket together after first positioning the chain over the crankshaft sprocket. Position the sprocket so that the marks made earlier line up. This is assuming that the engine has not been disturbed. The camshaft and crankshaft keys should both be pointed upward. If a new chain and/or gear is being installed, position the sprocket so that the timing marks on the chain align with the marks on the crankshaft sprocket and the camshaft sprocket (with both keys pointing up). The marks are on the right-hand side of the sprockets as you face the engine. The L18 has 42 pins between the mating marks of the chain and sprockets when the chain is installed correctly. The L20B has 44 pins. The 1977-78 L24 engine used in the 810 has 42 pins between timing marks. The L24 (1979-84), Z20E and Z20S engines do not use the pin counting method for finding correct valve timing. Instead, position the key in the crankshaft sprocket so that it is pointing upward and install the camshaft sprocket on the camshaft with its dowel pin at the top using the No. 2 (No. 1 on the L24) mounting hole and timing mark. The painted links of the chain should be on the right-hand side of the sprockets as you face the engine. See the illustration.
The factory guide refers to the pins you are to count in the L-series engines as links, but in the U.S., this is not correct. Count the pins. There are two pins per link. This is an important step. If you do not get the exact number of pins between the timing marks, valve timing will be incorrect and the engine will either not run at all, in which case you may stand the chance of bending the valves, or the engine will run very poorly.
- Install the chain tensioner and the front cover assembly.
If timing chain assembly uses chain guides these guides do not have to be removed to replace the timing chain. Check the timing chain for cracks and excessive wear.Diesel Engine
- Follow Steps 1-6 of the preceding Gasoline Engine procedure. You need not remove the fuel pump as detailed in Step 2.
- Install the crankshaft sprocket. Make sure that the mating marks on the sprocket face the front of the car.
- Install the timing chain and the camshaft sprocket together after first positioning the chain over the crankshaft sprocket. Position the cam sprocket so that the marks made earlier line up. This is assuming that the engine has not been disturbed. The camshaft and crankshaft keys should be pointing upward. If a new chain and/or gear is being installed, position the sprocket so that the timing marks on the chain align with the marks on the crankshaft and camshaft sprockets (with both keys pointing up). The marks are on the right-hand side of the sprockets as you face the engine. Insert the camshaft dowel pin into the No. 1 hole in the camshaft sprocket. Install and tighten the camshaft sprocket bolt.
- Install the chain guide (if removed) and the chain tensioner. Tighten the slack side (left side when facing the engine) chain guide mounting bolt so that the protrusion of the chain tensioner spindle is 0.
- Install the front cover assembly.
TIMING CHAIN ADJUSTMENT
When the timing chain stretches excessively, the valve timing will be adversely affected. There are three sets of holes and timing marks on the camshaft sprocket.
If the stretch of the chain roller links is excessive, adjust the camshaft sprocket location by transferring the set position of the camshaft sprocket from the factory position of No. 1 or No. 2 to one of the other positions as follows:
- Turn the crankshaft until the No. 1 piston is at TDC on the compression stroke. Examine whether the camshaft sprocket location notch is to the left of the oblong groove on the camshaft retaining plate. If the notch in the sprocket is to the left of the groove in the retaining plate, then the chain is stretched and needs adjusting.
- Remove the camshaft sprocket together with the chain and reinstall the sprocket and chain with the locating dowel on the camshaft inserted into either the No. 2 or 3 hole of the sprocket. The timing mark on the timing chain must be aligned with the mark on the sprocket. The amount of modification is 4° of crankshaft rotation for each mark.
- Recheck the valve timing as outlined in Step 1. The notch in the sprocket should be to the right of the groove in the camshaft retaining plate.
- If and when the notch cannot be brought to the right of the groove, the timing chain is worn beyond repair and must be replaced.