PISTON RINGS

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.