Here are timing chain installation instructions with photos:
Before beginning any disassembly procedures, position the No. 1 piston at TDC on the compression stroke.
Remove the timing chain cover. Remove the cylinder head cover.
With the No. 1 piston at TDC, the timing marks on 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 see 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 section following for details.
With the timing marks on the camshaft 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 reused, 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! The crankshaft sprocket can be removed with a puller, if necessary. There is no need to remove the chain guide unless it is being replaced.
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 previously line up. This is assuming that the engine has not been disturbed. The camshaft and the crankshaft keys should both 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 sprocket (with both keys pointing up). The marks are on the right hand side of the sprockets as you face the engine. 1970-73 L16 and L18 engines have 42 pins between the mating marks of the chain and sprockets when the chain is installed correctly. 1974-80 L18 and L20B engines have 44 pins.
The factory refers to the pins as links, but in American terminology this is incorrect. Count the pins. There are two (2) pins per chain 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 or will run very badly.
Z20, Z22, Z24 and Z24i engines do not use the pin counting method for finding correct valve timing. Instead, set the timing chain by aligning its mating marks with those of the crankshaft sprocket and camshaft sprocket. The camshaft sprocket should be installed by fitting the knock pin of the camshaft into its No. 2 hole. And the No. 2 timing mark must also be used.
Install the camshaft sprocket bolt and tighten it to 87-116 ft. lbs. (118-157 Nm).
Install the chain guide and tensioner. Adjust the protrusion of the chain tensioner spindle to zero clearance. Tighten the bolts to 4-7 ft. lbs. (6-10 Nm).
With a new seal installed in the timing chain cover and a light coat of oil applied to the seal, install the timing cover. Start the engine and check for any leaks. Check the ignition timing.
Fig. 1: Crankshaft sprocket removal-all 4-cylinder gasoline engines
Fig. 2: When installing the timing chain, count the number of links-L16, L18 and L20B engines
Fig. 3: Timing chain and sprocket alignment-Z20, Z22, Z24 and Z24i engines
Fig. 4: Installing the timing chain tensioner-all 4-cylinder gasoline engines
Fig. 5: Crankshaft sprocket installation-Z20, Z22, Z24 and Z24i engines
Fig. 6: Removing the camshaft gear retaining bolt
Fig. 7: View of the camshaft gear retaining bolt
Fig. 8: Removing the camshaft gear and timing chain
Fig. 9: Removing the timing chain tensioner mounting bolts
Fig. 10: View of the timing chain tensioner assembly
Fig. 11: Removing the timing chain assembly oil thrower
Fig. 12: Removing the oil pump drive gear
Fig. 13: Marking the oil pump drive gear for correct installation
Fig. 14: Marking the timing chain if necessary
Fig. 15: Removing the crankshaft sprocket
Fig. 16: Removing the timing chain guide bolt
Fig. 17: Removing the timing chain guide
Fig. 18: Cleaning the timing chain case cover area
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The only reasons for timing chain not going back on is either the chain is not being installed while already on the crankshaft sprocket, then timing chain and cam sprocket installed together, or the head wasnt installed correctly causing incorrect distance between the camshaft and crankshaft, or the tensioner was installed before chain. The chain cant shrink and you would be able to tell if it was kinked. That only leaves installation procedure.
"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 previously line up. This is assuming that the engine has not been disturbed. The camshaft and the crankshaft keys should both 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 sprocket (with both keys pointing up)"
Make sure the person installing the chain is following these directions
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