Why must cylinder ring ridges must be removed before removing the piston and connecting rod?
The piston rings will catch on the rings, making it difficult to remove. If the ridges are not removed damage could occur to the piston and/or cylinder.
What are two safety precautions to take while using rotary wire brush, when removing carbon buildup in a cylinder?
- Where proper PPE
- Make sure the brush is suitable for the tool being used
At what piston position, should the piston and rod be removed at?
Bottom Dead Center (BDC)
Why is it necessary to remove piston cooling nozzles (some engines) when servicing the pistons?
It prevents damage to the cooling nozzles.
When removing piston rings, what is the purpose of a ring expander?
The ring expander opens the piston rings just enough to slide up off the piston, thus preventing any damage to the rings and piston.
What parts of a piston should not be bead blasted?
All parts of the piston should be avoided, except for the crown, dome, and alloy ring grooves (aluminum pistonss).
What care should be taken when scraping carbon out of piston ring grooves?
Care should be taken to ensure metal is not scraped off with the carbon
What tool is used to properly measure the ware in a KEYSTONE piston ring groove?
A ring groove wear gauge
Pistons should be visually inspected for sings of what?
- Cracking on the crown
- Cracking in the piston ring bore
- Scoring/wear on the skirt
- Erosion in the ring grooves
- De-bonding of inserts (alloy ring grooves in aluminum pistons)
A piston skirt is measured about midway down, and at what angle to the piston pin bore?
90°
What are three problems that will occur as a result of worn piston ring grooves?
- Poor sealing will occur, resulting in blow by
- Rings will break due to excess movement
- Oil consumption will occur due to improper sealing
Calculate the piston clearance:
Piston skirt diameter - 4.9985”
Cylinder bore diameter - 5.0017”
Clearance = 5.0017" - 4.9985" Clearance = 0.0032"
If a piston is installed with insufficient clearance between the skirt and cylinder wall, what would a likely outcome be?
Scuffing and scoring would occur, and eventual piston seizure. This is a result of the tight fit, improper lubrication, and excessive heat buildup.
Piston PINS should be measured to determine:
Minimum outside dimension and out of round. The minimum dimension will give a good indication of pin wear, when compared to original specs.
Calculate the piston pin clearance:
Piston pin diameter - 2.4997”
Piston pin bore diameter - 2.5012”
Pin clearance = 2.5012” - 2.4997”
Pin clearance = 0.0015”
What methods can be used to check a connecting rod for cracks?
- Visual inspection (naked eye)
- Dye check
- Magnetic particle check
- Fluorescent magnetic particle (Magnaflux)
What are the three measurements that must be made to determine the condition of the large end bore, on a connecting rod?
- Bore size
- Out of round
- Taper
What will happen if a connecting rod is bent?
- Decreased engine efficiency due to a loss of compression (reduced compression ratio)
- Uneven wear on the piston and its components
Unless otherwise stated, what is the proper position to install a full floating piston snap ring?
The ends should point down, and sharp edge facing out.
If a full floating piston has an interference fit at room temperature, how would you remove it?
Heat the piston to expand the bore, then remove the pin.
Explain how to position a piston ring, in a cylinder bore, to measure end gap:
Push the piston ring into an unworn area of the cylinder bore, with the gap facing up. Rotate the ring so it is horizontal and completely touching the bore wall. If desired, use a piston (upside-down) to gently push against the ring, to ensure it is flat.
What would happen if a piston ring was installed without sufficient end gap?
The ring would seize up in the bore, as there would not be enough excess room for heat expansion.
Why are piston ring end gaps staggered before the piston is installed?
Proper staggering minimizes the amount of combustion pressure, combustion gas, and oil leakage getting past the rings.
What is important to check when installing connecting rod bearing shells?
The alignment of the locating tangs and oil holes.
