Chevrolet Full-size Cars 1968-1978 Repair Guide

Piston Ring and Wrist Pin

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REMOVAL





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Fig. Fig. 1 Inline six-cylinder engine's piston-to-rod relationship



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Fig. Fig. 2 Small block V8 engine's piston-to-rod relationship



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Fig. Fig. 3 Big block V8 engine's piston-to-rod relationship



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Fig. Fig. 4 Exploded view of the piston assembly and related components



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Fig. Fig. 5 Removing the wrist pin clips using a pair of needlenose pliers

Some of the engines covered in this guide utilize pistons with pressed-in wrist pins; these must be removed by a special press designed for this purpose. Other pistons have their wrist pins secured by snaprings, which are easily removed with snapring pliers. Separate the piston from the connecting rod.

PISTON RING END-GAP



Piston ring end-gap should be checked while the rings are removed from the pistons. Incorrect end-gap indicates the wrong size rings are being used; ring breakage could occur.

Compress the piston rings to be used in a cylinder, one at a time, into that cylinder. Squirt clean oil into the cylinder, so that the rings approximately 1" below the deck of the block (on diesels, measure ring gap clearance with the ring positioned at the bottom of ring travel in the bore). Measure the ring end-gap with a feeler gauge, and compare to the Ring Gap chart in this information. Carefully pull the ring out of the cylinder and file the ends squarely with a fine file to obtain the proper clearance.

PISTON RING SIDE CLEARANCE & INSTALLATION





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Fig. Fig. 6 Ring gap locations for all engines



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Fig. Fig. 7 Checking the ring-to-ring groove clearance

Check the pistons to see that the ring grooves and oil return holes have been properly cleaned. Slide a piston ring into its groove, and check the side clearance with a feeler gauge. Make sure you insert the gauge between the ring and its lower land (lower edge of the groove), because any wear that occurs forms a step at the inner portion of the lower land. If the piston grooves have worn to the extent that relatively high steps exist on the lower land, the piston should be replaced, because these will interfere with the operation of the new rings and ring clearance will be excessive. Piston rings are not furnished in oversize widths to compensate for ring groove wear.

Install the rings on the piston, lowest ring first, using a piston ring expander. There is a high risk of breaking or distorting the rings, or scratching the piston, if the rings are installed by hand or other means.

Position the rings on the piston as illustrated; spacing of the various piston ring gaps is crucial to proper oil retention and even cylinder wear. When installing new rings, refer to the installation diagram furnished with the new parts.

 
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