1 / 29

Chapter 12

Chapter 12. Pistons, Rings, and Connecting Rods. Objectives. Analyze wear and damage to pistons, rings, pins, and rods Select most appropriate repairs to perform Describe related theory of pistons, rings, wrist pins, connecting rods, and related parts. Cast and Forged Pistons.

gkerns
Download Presentation

Chapter 12

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 12 Pistons, Rings, and Connecting Rods

  2. Objectives • Analyze wear and damage to pistons, rings, pins, and rods • Select most appropriate repairs to perform • Describe related theory of pistons, rings, wrist pins, connecting rods, and related parts

  3. Cast and Forged Pistons • Cast are most common • Forged are used for heavy duty and high performance application • Forged pistons are 70% stronger than cast • Cast pistons should not be used above 5,000 rpm

  4. Piston Head and Ring Grooves • Diameter of piston head is typically .022" less than diameter of skirt • Top piston ring is placed as high as possible to prevent piston slap • Top ring groove suffers most abuse • Typically have three ring grooves

  5. Piston Head and Ring Grooves

  6. Piston Expansion Control • Aluminum piston expands at about twice the rate of the cast iron block

  7. Piston Expansion Control • To help prevent expansion: • Most piston skirts are tapered • Skirt is cam ground to allow for a tighter cylinder clearance • Cast pistons have a spring loaded steel cast • This helps the piston expand along wrist pin during warm up

  8. Piston Wear Problems • Scuffing on the piston skirt caused from excessive idling or by lugging the engine • Scuffing caused by cylinder wall hot spots

  9. Piston Wear Problems • Overheated piston because of cooling system problems or combustion problems • Piston head wear above top ring due to excessive cylinder clearance • Wear above wrist pin due to a bent rod

  10. Piston Service • Pistons should be removed from the connecting rod • Wrist pin bores need to be protected • Use a soda blaster to remove carbon • Excessive blasting can distort ring grooves

  11. Cleaning Ring Grooves • Removal of carbon from ring grooves: • Soda blaster • Piece of broken ring • Ring groove cleaner

  12. Cleaning Ring Grooves • Carbon must be removed or new rings might not compress enough to enter cylinder

  13. Cleaning Ring Grooves

  14. Piston Rings • Most engines use two compression rings and one oil ring • Seal compression helps cool piston and control oil consumption • Top sealing ring is exposed to pressures of 1,000 psi

  15. Ring Size Terminology • Width • Height of ring • Radial thickness • Depth of the ring into groove • Flutter • Inertia from high speed causes ring to stay against top of ring groove

  16. Ring Size Terminology

  17. Compression Ring Design • Napier Rings • Steeped ridge provides “squeegee” edge • Torsional Twist Rings • Chamfered on top inside edge • Reverse Twist Rings • Machined in lower inner corner • Barrel-Faced Ring • Less likely to cause ring ridge

  18. Piston Ring Materials and Coatings • Cast iron rings • Moly rings • Chrome rings • Premium ring combination

  19. Piston Ring Materials and Coatings • Ductile iron rings • Steel rings • Plasma ceramic • Pressure-balanced rings

  20. Oil Control Rings • Oil ring failure • Plugged because of blow by leaking past compression rings • Most engines have only one oil ring located below compression rings • Oil ring contributes most friction to engine

  21. Oil Control Rings

  22. Ring Wear • Main cause of ring wear is abrasion • If wear is due to dirty air entering the engine • Top compression will show more wear • If ring wear is due to abrasives in the oil • Lower rings will show more wear

  23. Installing Rings on Pistons • Use a ring expander to install rings • Identification marks facing up • If one compression ring is installed upside-down • Oil consumption may double • Gaps should not line up with the gaps in other rings

  24. Installing Rings on Pistons

  25. Wrist Pins • Piston pin • Used to attach piston to connecting rod • Lack of lubrication can damage pin • Lubricated from either a hole in the top of the pin boss or through an angle-drilled hole that runs from the wrist pin • Can be pressed in or held in with retainers

  26. Wrist Pins

  27. Connecting Rods • Made from forged or cast steel • Some racing rods are made from forged aluminum • Generally made in an I-beam shape for strength

  28. Rod Service • Inspect rods for any obvious cracks, bends, or heat damage • Check rods suspected to be bent or twisted

  29. Rod Service

More Related