How to Check Timing Chain Wear on a Small Block Chevy

by Lee Sallings
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As the timing chain in the small-block Chevy engine wears, it stretches and becomes unable to accurately control valve and ignition timing. The result is sluggish performance and frequent backfire through the intake manifold caused by the uncontrolled changes in timing. Checking the timing chain for excessive wear is straightforward and well within the ability of the average home mechanic.

Step 1

Clean the timing marks on the timing tab located just above the harmonic balancer on the engine block. Clean the timing mark on the harmonic balancer and mark it with a white crayon.

Step 2

Remove the distributor cap from the distributor, located at the rear of the engine, and turn the engine counterclockwise by hand until the timing mark on the balancer lines up with the TDC (Top Dead Center) mark on the timing tab.

Step 3

Turn the engine clockwise with the crankshaft socket and 1/2-inch drive ratchet until the rotor just starts to move and stops turning. Note the degree of rotation indicated by lining the timing mark on the harmonic balancer with the marks on the timing tab.

Step 4

Calculate the difference between the two readings. The difference between the two indicates the amount of slack in the timing chain. Three to five degrees is normal, and more than 10 degrees is excessive. More than 10 degrees of slack indicates that it is time to replace the chain and gears.

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