Test 1 Flashcards
What is one of the main functions of a piston?
Transmit force to the crankshaft through the connecting rod
Why is the shape of the piston dome important?
To help create turbulence ensuring full combustion
How does a ‘Cam Ground’ piston work?
It becomes oval as the engine warms up
Why would the top ring groove in an aluminum piston have a steel or nickel-chrome alloy insert installed?
It reinforces and reduces wear in the groove
What is a full floating piston pin?
A pin that can rotate freely in the piston and the connecting rod
What is the advantage of a two-piece piston?
Both the skirt does not absorb the force of combustion and bending stress on the piston pin is reduced
What is the procedure for installing a full floating piston pin that is tight in the piston pin bore?
Use a press to push the piston onto the pin
What are the common types of oil cooling for pistons?
Splash, shaker, swirl, circulation
What are the functions of a piston ring?
Seal, cool, center
What three factors combine to produce an effective seal between the ring and the cylinder wall?
Ring tension, oil film, cylinder pressure
What is the main purpose of ring end gap?
Allows a metered amount of blow by into the crankcase
The ring end gap is crucial for controlling the pressure within the combustion chamber and preventing excessive pressure build-up.
Most diesel engines today use what type of oil control ring?
Two Piece
Two-piece oil control rings are common due to their efficiency in managing oil consumption.
What does a coil or wave expander do for the oil control ring?
Ensures the oil ring has enough tension on the cylinder wall
This helps maintain effective oil control and reduces oil consumption.
What is the ‘General Rule’ when installing piston rings?
Install them so at the end gaps are lined up
Proper alignment of ring gaps is critical to prevent excessive blow-by and maintain compression.
How is oil controlled in a two-stroke engine?
2 stroke engines have inlet ports on the cylinder wall
This design allows for a different oil management strategy compared to four-stroke engines.
What are common types of ring joints?
- Butt
- Angle
- Step
The choice of ring joint affects the sealing and performance of the piston rings.
What is used to remove the wear ridge on a cylinder liner?
Ridge reamer
Removing the wear ridge is essential for proper piston and ring installation.
What important step should be followed when performing an ‘in Frame’ overhaul?
Cover oil holes and coolant passages to prevent contamination
Preventing contamination is vital for the longevity and performance of the engine after an overhaul.
What is the best way to remove a compression ring off of a piston?
Use a universal or fixed expander and slide the ring off the bottom of the piston
This method minimizes the risk of damaging the ring or piston.
When should a two-piece piston be disassembled?
Before cleaning and inspection
Disassembling before cleaning ensures thorough inspection and maintenance.
What should be done before removing a piston?
Measure the clearance between the piston and liner
This measurement is crucial for ensuring proper fit and function after reassembly.
What type of damage would be seen on the piston skirt?
- Erosion
- Scuffing
- Scoring
Damage to the piston skirt can affect engine performance and longevity.
What could cause a piston to become overheated?
Insufficient lubrication or excessive load
Overheating can lead to serious engine damage and failure.
Why is the piping diameter measurement taken 90 degrees?
The measurement provides a true indication of diameter
Measuring at 90 degrees ensures accuracy in assessing wear and fit.
How is the keystone ring groove measured for wear?
Using a micrometer to assess groove depth and width
Accurate measurement of wear is essential for determining if replacement is necessary.
What is the method used to measure the keystone ring groove for wear?
With a ring groove wear gauge
Other tools such as feeler gauges, depth micrometers, and dial gauges could also be used in different contexts.
What precautions should be taken when bead blasting a piston pin?
Tape off bearing surfaces
Other considerations include turning down the pressure and avoiding aiming the stream at one spot.
What does ridging refer to in relation to a piston pin?
Uneven, extreme wear on the piston pin
It can also relate to damage on the connecting rod bores.
What is a sign of excessive piston pin clearance in an engine?
A ‘double knock’ from an engine
This symptom indicates potential issues with engine performance.
In what orientation should a piston pin snap ring be installed?
Gap toward the major thrust side
Proper installation orientation is crucial for engine performance.
What two piston ring measurements must be made during a rebuild?
End gap and side clearance
Accurate measurements are essential for ensuring engine efficiency and longevity.
What is the main purpose of the oil ring?
Control the amount of oil on the cylinder walls
It plays a critical role in engine lubrication and performance.
How should ring end gaps be positioned on each piston?
Staggered evenly apart
This positioning helps to maintain effective sealing and performance.
What are the two general types of ring compressors?
Fixed and adjustable
Each type serves different purposes during engine assembly.
