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Mechanics
Chpt. 14 Engine Bottom End Construction
| Question | Answer |
|---|---|
| What are engine cylinder blocks normally made of? | cast iron or aluminum |
| Does cast iron or aluminum dissipate heat better? | aluminum |
| If you want to reduce the weight and increase fuel economy what would use to make a block? | use aluminum blocks |
| Dry Sleeve | relatively thin and is not exposed to engine coolant |
| Wet Sleeve | is exposed to engine coolant and must withstand combustion pressure and heat without the added support of the cylinder block |
| What is line boring? | a machining operation that cuts a series of holes through the block for the crankshaft bearings |
| What is a slipper skirt? | provides clearance between the piston and the crankshaft counterweights |
| Define piston diameter. | the distance measured across the sides of the piston |
| What is meant by the term pin hole diameter? | the distance measured across the inside of the piston hole pin |
| What is a ring groove width? | the distance measured froml the top to the bottom of the ring groove |
| What is the purpose of piston taper? | is used to maintain the correct piston-to-cylinder clearance |
| What does a piston head shape generally refer to? | the contour of the piston top |
| The head of a flat-top piston is parallel with what surface? | the blocks deck surface |
| Define valve reliefs. | small indentations either cast or machined into the piston crown to porvide ample piston-to-valve clearance |
| What kind of piston is a two-piece design controlled by engine oil pressure? | variable compression piston |
| What piston is slightly out-of-round when viewed from the top? | cam ground |
| Automotive pistons usually use 2 different rings. How many of each would you use and what are they called? | 2 compression rings 1 oil ring |
| What do compression rings do? | prevent leakage into the crankcase and wipe oil from the cylinder walls |
| Explain ring seating | the initial ring wear that makes the ring perfectly match the surface of the cylinder |
| Name two basic oil ring designs | rail-spacer type and one-piece type |
| What is the function of a piston's oil ring? | to keep the crankcase oil out of the combustion chamber |
| What is the piston ring width? | the distance from the top of the ring to the bottom of the ring |
| What is the piston ring radial wall thickness? | the distance from the face of the ring to its inner wall |
| What is the piston ring gap? | the distance between the ends of the ring when installed in the cylinder |
| When are soft ring coating desirable? | when they are used in cylinders that are slightly worn |
| When are chrome or moly hard ring coatings used? | in new and freshly machined cylinders that are perfectly round |
| What are piston pins normally made of? | case-hardened steel |
| What is case-hardening? | a heating and cooling process that increases the wear resistance of the piston pin. |
| What kind of pin is forced tightly into the connecting rod's small end? | press-fit |
| What kind of pin is secured by snap rings and is free to rotate in both the rod and piston? | full-floating pin |
| What is the purpose of piston pin offset? | helps quieten the piston during use |
| What are most connecting rods made of? | steel |
| Explain low-inertia parts | are light parts that will accelerate quickly |
| What is the purpose of a hole machined through the entire length of a drilled connecting rod? | supplies oil to the piston pin |
| Connecting rod numbers used for what? | to ensure proper location of each connecting rod in the engine |
| Define powdered metal forging | process that forms the rough shape of the part out of metal powder before final shaping in a powerful forge. |
| What are engine crankshafts usually made of? | cast iron or forged steel |
| Crankshafts in turbocharged or diesel engines are made of? | forged steel |
| Where does the oil enter the crankshaft at? | main bearings |
| With a V-type engine, how many connecting rods bolt to each rod journal? | two |
| Define a fully countweighted crankshaft | has weights formed opposite every rod journal |
| Define a partially counterweighted crankshaft | has weights formed opposite the journals in the center portion of the shaft only |
| What are the three basic types of engine bearings? | camshaft bearing, connecting rod bearing. crankshaft main bearing |
| What is bearing load strength? | the bearings ability to withstand pounding and crushing during engine operation |
| What is bearing conformability? | the bearing ability to adjust to imperfections in the journal surface |
| Whati is bearing embedability | the bearings ability to absorb dirt, metal, or other hard particles |
| What is bearing corrosion resistance? | the bearings ability to withstand being acted on by acids, water and other impurities in the eingine oil |
| What is the purpose of bearing crush? | used to prevent the bearing from spinning inside its bore during engine operation |
| What is bearing spread? | used on split-type engine bearings to hold the bearing in place during assembly |
| Describe a standard bearing. | has the original dimensions specified by the engine manufacturer for a new, unworn, or unmachined crankshaft |
| What is an undersized bearing used for? | on a crankshaft journal that has been machined to a smaller diameter |
| What do bearing locating lugs or dowels do? | positon split bearings in their bores |
| Connecting rods and main bearing are available in what undersizes? | 0.010", 0.020", 0.030", 0.040" |
| How are engine bearings lubricated? | bearing oil holes or grooves in the engine bearings allow oil to flow through the block and the clearance between the bearing and the journal |
| What is the function of a main thrust bearing? | limit crankshaft end play |
| Describe the purpose of a rear main bearing oil seal | prevents oil leakage around the back of the crankshaft |
| Name three types of rear main bearing oil seals | two-piece neoprene seal, one-piece neoprene seal, wick or rope seal |
| What is a rope (wick) oil seal? | a woven rope filled with graphite |
| What does select fit mean? | some engine parts are selected and installed in a certain position to improve the fit or clearance between parts |
| What are balancer shafts used for in some engines? | to cancel the vibrating forces produced by crankshaft, piston and rod movement |
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mechanics
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