1. Engine Diagnosis and Service: Block, Crankshaft, Bearings, and Lubrication System
Chapter 53

2. Objectives Analyze wear and damage to the cylinder block
Select and perform the most appropriate repairs to the block, crankshaft, and bearings
Analyze wear and damage to the crankshaft and bearings
Analyze wear and damage to lubrication system parts
Select and perform the most appropriate repairs to the lubrication system

3. Introduction
Cylinder block can usually be reused after certain service procedures are performed
Blocks with excessive wear
Some will have to be bored oversize to be used with new, larger pistons
Some may need only cleaning and minor service
Some may need major service

4. Cleaning the Block and Oil and Water Plug Removal
Block must be thoroughly cleaned
Removable parts must be removed
Oil and water plug removal
Female plug: removed by plug driver
Male plug: removed with socket
Core plugs: knocked out from rear
Clean oil galleries and the block
Remove deposits in oil galleries and supply holes
Check for cracks
Check block for cracks in cylinder bores

5. Oil and Water Plug Installation and Inspect and Clean Lifter Bores
Reinstall plugs after cleaning galleries
Do not over tighten threaded plugs
Pressed-fit oil gallery core plugs installed with red thread lock adhesive
Cross-stake outside of core holes with chisel
Inspect and clean lifter bores
Clean with brake hone turned by hand
Do not enlarge the lifter bore

6. Checking Main Bearing Bore Alignment
Heating and cooling of engine block results in misalignment of main bearing bores
Bearing bores are checked with dial bore gauge
Vertical should not be larger than horizontal
Line honing realigns main bores
Main caps ground on parting faces
Bores aligned by honing to original main bearing bore size
Removing too much metal moves the crank shaft up too far into block

8. Check the Deck Surface for Flatness and Clean All Bolt Holes
Clean deck surface of block with whetstone
Do not make surface too smooth
Check deck surface for flatness
Threads in the block must be clean
Chase threads with a tap
Failure to do this results in leaking head gasket
Head bolt holes run into water jackets, so threads may rust
Rusted steel is very hard

9. Inspecting Cylinder Bores
Cylinder bores wear in a taper and out-of-round fashion
Maximum wear is at 90 degrees to wrist pin
Different considerations determine cylinder bore wear limits
Taper wear
Causes end gaps of piston rings to change as the rings move up and down the cylinder
Out-of-round wear
Caused by piston rocking on wrist pin at TDC and BDC

10. Measuring the Bore Several methods Dial bore gauge
Telescoping gauge and micrometer
Inside micrometer
Cylinder dial bore gauge
Dial bore gauge
More accurate

11. Deglazing the Cylinder Bore
Cylinders become glazed where piston rings contact cylinder wall
Glaze removed with lacquer thinner, carburetor cleaner, glaze breaker
Drill with rotation speed of 450 rpm recommended for deglazing cylinders
Two types of glaze breakers:
Spring-loaded glaze breaker
Ball-type glaze breaker (flex hone)

12. Clean the Block of Grit Clean block after glaze breaking or honing
Grit left will wear parts
Clean with stiff brush and hot soapy water
Brush can be used by hand or with air drill
Check for cleanliness with clean cloth
After cleaning: grit may be in crankcase area
Ferrous parts
Coated with oil to prevent rusting
Rusting begins immediately after cleaning

13. Boring for Oversized Pistons
Cylinders deglazed only if they do not have excessive bore taper
Damaged cylinders should be rebored and honed
Piston oversizes
Top of oversize piston is stamped with oversize amount

14. Block Distortion
Block castings distort when heads and main cap bolts are torqued
Distortion results in piston scuffing and slap
Boring stand
Supports block at main bearing bores
Torque plate is sometimes torqued to top of block
Stresses the block and simulates assembly conditions
Main caps should be torqued in place

15. Honing After Boring Machine shop Pistons vary in size within a set
Bore cylinders to desired bore size
Honing after boring provides better surface for new rings
Pistons vary in size within a set
Must be fitted to the bores
After boring and honing
Top of bore is chamfered by 1/16”
New rings enter cylinder without chipping

16. Sleeves Sleeves repair cracked or damaged cylinder
Recommended interference fit: per inch
Sleeve pressed into the bore
Top finished flush with block
Inside diameter bored to finished size
Popular sleeving method
Bottom of sleeve rests on step

18. Cam Bearing Installation (Cam-in-Block Engines)
Cam bearings are interference fit
Outside diameter larger than bearing bores in the block
Clean bearing bores before installing
Several types of cam bearing removal and installation tools
Universal type installation tool most popular
Follow manufacturer’s recommendations when positioning the oil hole

19. Front Cam Bearing Installation
Older pushrod engines
Timing sprockets are chain lubricated from front cam bearing
Often installed past block surface
Oil channel throws oil onto the timing chain
Check fit of bearing
After installing bearing: install cam and turn it
Special flex hone is available for honing small amounts off cam bearings
Scotch BriteTM can be used to polish cam bearing surfaces

20. Checking Crankshaft Condition
Check crankshaft for straightness
Keep bearings in position order during disassembly
Bent crank indicated when one bearing wears more than others
Checking for cracks
Ring counterweights with light tap of hammer
Dull sound indicates crack
Crankshaft is broken
Check vibration damper for damage

23. Crankshaft and Bearing Wear
Characteristics
Bearings have loaded and unloaded halves
Main cause of short bearing life is dirt
Journals wear out-of-round or become tapered
Rod journals exhibit taper wear due to misalignment of connecting rod
Thrust bearing wear and failure occur when load is continuous
Improper clutch adjustment
Driver riding the clutch

24. Crankshaft Journal Tolerance and Regrinding the Crankshaft
Tolerance: range of wear specifications
Crankshaft: usually reground undersize
Rod journals and main journals may be ground to different undersizes

25. Measuring Bearing Clearance with Plastigage
Checked with plastigage or micrometer
Do not rotate crankshaft while plastigage in place
Cap is torqued: plastic string flattens
Wider string: indicates less clearance
Actual clearance
Can also be determined by micrometer
Some manufacturers use select-fit bearings on new engines
Those that have not been previously rebuilt

26. Lubrication System Service
Engine oil pressure
Indicates condition of lower end
Low pressure at idle indicates excessive clearance or worn pump
Long periods of idling with low oil pressure leads to cylinder wall lubrication problems
Engine with too much oil pressure
Oil consumption problems
Bearing lining material washed off

27. Checking Oil Pumps for Wear
Use feeler gauge to check oil pump for wear
Follow manufacturer specifications
Rotor pump clearance tolerances
0.010" between inside and outside rotors
0.014" between outside rotor and housing
Gear pump clearance checked by inserting plastigage between cover and gear ends
End clearance less than 0.003"
Side clearance less than 0.005"

28. Oil Pump Screen Service
Oil pump screen: check to be sure it’s clean
Be sure bypass is not stuck permanently open on newly cleaned screens
Screen should not have loose or damaged wire mesh

29. Oil Pump Failure Causes of pump failure
Improper maintenance
Foreign objects get into pump
Deteriorated valve guide seals
Bottom of pump requires gasket only if mounted on outside of block
Bolt-on oil pickup screens require gasket
Replace screens that do not fit tightly, are damaged, or dirty

30. Installing the Oil Pump
Fill oil pump cavity with lubricant
Turn by hand to be sure it is not damaged