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CHAPTER 11

CHAPTER 11. PISTON RINGS Page 295 Class Page 306 Lab. PISTON RINGS. Piston rings seal combustion pressures. Piston rings control oil consumption. Piston rings help cool the piston. Most modern engines use 2 compression & 1 oil rings. RING OVERSIZES.

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CHAPTER 11

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  1. CHAPTER 11 • PISTON RINGS • Page 295 Class • Page 306 Lab

  2. PISTON RINGS • Piston rings seal combustion pressures. • Piston rings control oil consumption. • Piston rings help cool the piston. • Most modern engines use 2 compression & 1 oil rings.

  3. RING OVERSIZES • Rings sizes are standard, .030”, .040”, .060”. • Metric sizes are standard, 0.50 mm, 0.75 mm, 1.0 mm,

  4. COMPRESSION RINGS • Compression rings are forced against the cylinder wall by combustion pressure at the top and back of the ring. • A square ring groove is a must. • Heavy rings tend to flutter.

  5. COMPRESSION RING DESIGN • There are many ring designs. See figure 10.32a. • The purpose of all designs is to cause the ring to contact the cylinder wall with a narrow part of the face. • This helps to cause quicker seating.

  6. TORSIONAL TWIST RINGS • A torsional twist ring is chamfered on its top inside edge. • A reverse twist ring is chamfered on its bottom inside edge. • A barrel faced ring has less than .001” curve to its face. • Low-tension rings - Have less depth than standard rings. • Deck plates are advised when honing thinwall blocks.

  7. RING COATINGS • Cast Iron is the common ring material. • Moly Rings - Have molten molybdenum sprayed on surface. • Chrome Rings - Have a chrome plated outer surface. • Moly barrel shaped top, reverse torsion second, 3 piece oil.

  8. PLASMA CERAMIC

  9. OIL CONTROL RINGS • 1 drop each power stroke = 1 quart every 2 miles. • Oil rings fail if they become plugged. • Reasons for failure improper maintenance, temp, lead. • Stainless steel expander with 2 chrome rails - common.

  10. RING WEAR • Major cause of ring wear is abrasion. • Causes of wear Honing grit, poor air filter, dirty oil. • Signs of abrasive wear are vertical scratches on rings.

  11. RING GAP CLEARANCE • Before installing rings check end gap. • Gap specs are in repair manual. • Gap will be .030” to much for each .010” error in size. • Too small a end gap can cause rings to seize in bore. Page 312 Fig. 11-67

  12. INSTALLING RINGS ON PISTONS • Rings may be installed by hand. • Rings may be installed with a ring expander. • Do NOT spiral rings onto pistons. • Do NOT overexpand rings during installation. • Install rings with I D marks up. Page 312 Fig. 11-70

  13. RING GAP POSITIONS • Place gaps at opposite sides of piston. • Dana says the reason for staggering gaps is to prevent scuffing. • Many opinions on gap placement. Page 315 Fig. 11-73

  14. OIL RING GAPS • Do NOT overlap ends of the expander. • Expander end gap over pin. • Rail end gaps 180 degrees apart.

  15. WRIST PINS • Pistons attach to rods with pins. • Oversize pins are not common today. Page 311 Fig. 11-64

  16. PIN RETAINING METHODS • Press fit is the most common. • dismount with a press and proper adapters. • Install with rod furnace.

  17. PIN RETAINING METHODS • Full floating pins - high performance. • Uses retaining rings to hold pin in place. • Opening in lock ring should face bottom of piston. • Be sure install piston on rod correctly.

  18. CONNECTING RODS • Made from forged or cast steel.

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