1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 14
Lesson 3
Engine Bottom End
Construction

3. Contents Crankshaft construction Engine bearing construction
Rear main bearing oil seal construction
Select-fit parts
Balancer shafts

4. Crankshaft Construction
Engine crankshafts are usually made of cast iron or forged steel
Forged steel crankshafts are needed for heavy-duty applications
turbocharged or diesel engines

5. Crankshaft Oil Passages

6. Crankshaft Oil Flow
Oil enters the crankshaft at the main bearings and passes through holes in the main bearing journals
Oil then flows through passages in the crankshaft and out to the connecting rod bearings

7. Engine Bearing Construction
There are three basic types of engine bearings:
crankshaft main bearings
connecting rod bearings
camshaft bearings

8. Engine Bearings

9. Crankshaft Oil Passages

10. Bearing Construction Steel is used for the body
Alloys are plated over the backing to form the bearing surface

11. Bearing Crush
Used to help prevent the bearing from spinning inside its bore
The bearing is made slightly larger than the bearing bore
When the rod or main cap is tightened, the bearing ends press against each other, locking the bearing in place

12. Bearing Crush

13. Bearing Spread
Used on split-type engine bearings to hold the bearing in place during assembly
The distance across the parting line of the bearing is wider than the bearing bore
bearing spread causes the bearing insert to stick in its bore when pushed into place

14. Standard Bearing
Has the original dimensions specified for a new, unworn, or unmachined crankshaft
May have the abbreviation “STD” stamped on its back

15. Undersize Bearing
Used on a crankshaft journal that has been machined to a smaller diameter
Available in undersizes of 0.010", 0.020", 0.030" and sometimes 0.040"
Undersize is normally stamped on the back of the bearing

16. This bearing is for a journal that has been machined 0.010" undersize
Undersize Bearing
This bearing is for a journal that has been machined 0.010" undersize

17. Bearing Positioning
A. Spread
B. Lug
C. Dowel

18. Bearing Oil Holes and Grooves
Holes allow oil to flow through the block and into the clearance between the bearing and the journal
Grooves provide a channel so oil can completely encircle the bearing before flowing over and out of it

19. Bearing Oil Holes and Grooves

20. Main Thrust Bearing and Washers
limits crankshaft end play
thrust flanges are formed on the main bearing sides, almost touching the thrust surfaces machined on the crankshaft
Thrust washers
used instead of a thrust bearing to limit crank end play

21. Main Thrust Bearing and Washers

22. Washers slide into place between the crankshaft and block
Thrust Washers
Washers slide into place between the crankshaft and block

23. Rear Main Bearing Oil Seal Construction
The rear main bearing oil seal prevents oil leakage around the back of the crankshaft

24. Rear Main Bearing Oil Seal
There are several different types of seals
These types include:
two-piece neoprene
one-piece neoprene
wick or rope seal

25. Two-Piece Neoprene Seal
Has a lip to trap oil and another lip that keeps dust and dirt out of the engine

26. Two-Piece Neoprene Seal
The seal fits into a groove cut into the block and rear main cap

27. One-Piece Neoprene Seal
The seal fits around the rear flange on the crankshaft

28. Wick Rear Oil Seal Woven rope filled with graphite
One piece of the rope seal fits into a groove in the block
Another piece fits in a groove in the main cap
Not as common on modern vehicles as one- and two-piece neoprene seals

29. Select-Fit Parts
Parts that are selected and installed in a certain position to improve the fit or clearance between parts
pistons are commonly selected to fit precisely into their cylinders
Because of select-fit parts, it is important that you reinstall parts in their original locations

30. Balancer Shafts
Used in some engines to cancel the vibrating forces produced by crankshaft, piston, and rod movement
Usually found on 4- and 6-cylinder engines
Usually, a chain is used to turn the shafts at twice crankshaft rpm

31. Shafts are supported on bearings and lubricated by pressurized oil
Balancer Shafts
Shafts are supported on bearings and lubricated by pressurized oil