u Metal foundation u Supports crankshaft and usually camshaft made of cast iron or aluminum, aluminum parts that wear will have metal inserts that are pressed or cast into the block. u Cylinder - round hole formed in block bored and honed to a fine finish, acts as a guide for piston and a container for the fuel charge
2. Cylinder Sleeves u Removable type or cast into block, wet and dry sleeves, u DRY pressed in block supported and surrounded, its full length - most common gas engine. u WET pressed in block supported only at top and bottom - cooling water comes in direct contact - heavier construction has sealing rings
Securing sleeves u When cast into block they usually have grooves in the outside of sleeves to secure it when pressed in it can have flange on top or will be held in only by friction of a pressed fit - head will keep it from coming up.
3. Piston u Sliding plunger in cylinder creates vacuum on intake stroke, compresses mixture on compression stroke transmits and contains the pressure of the firing stroke, cleans the cylinder of burned gases on the exhaust stroke.
Piston materials u aluminum - cast - most common, u forged- found in hi-performance engines
Expansion of Piston u If the piston is to loose it can cause piston slap, piston too loose in cylinder tips from side to side
Old styles of Piston u split skirt, skirt closes as piston warms up. u T slot, same as split skirt but has a T top to prevent heat of piston head transferring to skirt u steel strut, steel cast into aluminum piston steel expands less then aluminum and helps reduce expansion
New style u cam ground, minimum clearance on thrust sides egg shaped u thrust surface, side of piston that is at right angles to crank shaft and piston pin surface side that prevents tipping and supports the piston.
skirts u full skirt skirt goes all the way around piston not cut away. u slipper skirt, piston skirt cut away below piston pin for counter weights piston lighter reduces inertia load on bearings makes engine more responsive
piston temperature u head of piston up to and above 600' F bottom of skirt about 300'F, head of piston is.030 to.040 in smaller then skirt to allow for expansion top can be of different shapes
Piston Shapes u flat, dome, wedge, irregular - to help in exhausting burned gases u Piston pin boss, section of piston that supports piston pin inboard pin boss - most engines, out board pin boss - performance and competition u valve reliefs- small indentations machined into the top of the piston.
4. Piston rings u ride in grooves in piston head to seal the cylinder u types of rings, compression - prevent pressure leakage into the crankcase u different grooves, bevels, and chamfers causes internal stress causing scraper action on downward stroke taking any oil down that was missed by the oil ring
Piston rings u firing pressure forces top ring down for full face contact u inner groove usually goes up u outer groove usually goes down u material, rings made of cast iron, some are chrome plated, some are molybdenum coated or a grooved filled with moly, some rings are stainless steel
Oil control rings - u scrape oil off cylinder wall and send pack to crank case all new sets are three piece expander and two steel rings some old oil rings are just one ring break easy. u compression and oil control rings can have an expander ring to help force out the ring
Piston ring gap joints, most common - butt u lap and bevel have been used u some engines have a pin in piston ring groove to prevent ring from moving u piston ring gap usually.003-.004 for each inch of cylinder diameter
Ring Width u Distance from the top to the bottom of the ring
heat dam u groove in head of piston that prevents or lowers the amount of heat transferred to the top ring u top ring groove insert, metal insert cast into aluminum piston with piston groove cut out of insert to help prolong the life of the piston
5. Piston Pins u steel pin used to connect piston to connecting rod u case hardened, soft center.004 outside hardened highly polished
securing piston pins u 1. full floating pin, snap ring each end pin can turn in piston bosses and connecting rod may have bronze bushing
securing piston pins u 2. press fit (rod pressed into the connecting rod) pin turns in aluminum piston boss.
securing piston pins u 3. pin locked to rod by bolt not very common.
6. Connecting Rods u connect piston to the crankshaft upper end oscillates lower or large end rotates lower end must be split for installation of bearing and installation on crankshaft journal. before removing number rod and rod cap on same side with a number.
7. Insert Bearings u removable bearing split in two pieces for easy installation and removal
7. Insert Bearings u steel back with soft lining, coating can be of babbitt, copper-lead-tin or aluminum coating u locating tabs help keeps insert bearing from turning
Insert Bearings u crush height the.001 to.002 protruding above rod cap and rod that when bolted together forms the tight fit that prevents the bearing from turning. u An undersize bearing is used on a crankshaft that has been machined to a smaller size.
BEARING PERFORMANCE u load strength- must withstand pounding from compression and firing stroke u anti scuffing - if oil pressure is lost lining must be soft enough to prevent crankshaft journal from being scratched or scuffed u corrosion - must resist corrosion from vapors and acids in crankcase u conformation - must conform to shape of crankshaft journal
BEARING PERFORMANCE u embedability - must allow small particles to embed itself into bearing material so journal won't be scratched u temperature - must work equally well both hot and cold must transfer heat well u oil hole or groove for lubrication
BEARINGS u rod bearings, bearings in the connecting rod u main bearings, bearings that go where the main bearing cap hold the crankshaft in place.
THRUST BEARINGS u thrust bearing, has sides on to help prevent end play of crankshaft, sometimes use a separate piece for the side.
8. Crankshaft u Crankshaft, change reciprocating motion to rotary motion u made of Forged steel (should ring when you hit it with a hammer) or cast iron u counter balances, forged in crank to offset weight of crankshaft throw
Crankshaft u crankshaft throw, the part of crankshaft that the connecting rod fastens to also refer to as rod journal u crank main journal, by use of main bearing caps crankshaft is bolted to block u crankshaft is drilled so oil can be fed to main bearings and rod bearings, crankshafts are ground and highly polished
9. Harmonic Balancer or Vibration Damper u Helps absorb torsional vibration of crankshaft and smooth out firing pressure of each cylinder, 2 pieces with rubber plug or lining
10. Flywheel u 1. smooth out engine speed u 2. mounting surface for clutch u 3. starter motor engage ring gear to start engine u 4. carry engine through power strokes
11. Camshaft u opens the valves in engine cam lobes open the valves one per valve shape of lobe determines how long valve stays open and how far it opens also gear to drive the distributor and oil pump an eccentric may be ground or bolted onto cam to drive the fuel pump
12. Timing chain, belt and gears u drive chain or belt that connects the crankshaft gear(driving force) to the cam shaft gear (the driven force) camshaft turns at 1/2 crank shaft speed. u light duty chain, heavy duty - double roller, driven by all gears, crank gear - steel, cam gear - steel, aluminum, pressed fiber, plastic, must be aligned
tensioner for belt or chain Off of a 96 Olds chain drive Off a 75 Toyota 2TC chain drive
13. Valves u device used to open and close the valve port, engines have 2 3 or 4 valves per cylinder u some valves have a special hard facing on the face stellite faced valves
Valves u valve faces are ground at different angles 29- 30 and 44-45 most common. interface angle valve face 44 seat 45, exhaust valve may climb out of seat u cooling, heat dissipates through valve seat and valve guide some valves (heavy duty truck) are sodium filled to help transfer heat.
CAUTION: u SODIUM, IF DROPPED INTO WATER WILL BURST INTO FLAMES WILL CAUSE SERIOUS BURNS IF IT GETS ON TO YOUR SKIN.
14. Valve seat u Part of head or block that valve face comes in contact with to seal cylinder. Can be part of head or an insert that is pressed in. most now are hardened seats valve seat angle 30 and 45
15. Valve springs u closes valve when lifter comes off cam lobes some valves use 2 springs per valve, Must measure valve spring installed height, coil bind - spring can only go together so far.
16. Valve spring retainer u holds spring in place with a valve lock or keeper
Valve keepers u holds valve in place maybe called a stem lock
Valve Stem seals u Valve seals prevent oil from being drawn into the engine. Deflector seals usually called Umbrella seals and a Positive seal are the most common types. GM uses a O-ring on there engines.
17. Valve guide u hole through which valve passes to keep it in proper alignment can be cast into head or pressed in must have.002 -.003 clearance
18. Valve lifter u mechanical - solid u lifters are solid or hollow made of cast iron bottom that contacts camshafts is hardened adjustment is taken care of in rocker arms on most engines some lifters are adjustable.
Hydraulic Valve lifter u Hydraulic, self adjusting has zero valve lash clearance(No space between parts), use engine oil under pressure to operate are quieter then solid lifters operation, may use flat check valve or ball.
Hydraulic Valve lifter u Roller Lifter - has a small roller that rolls on the camshaft.
19. Lifter guide u bore in block that contain lifter has oil passage in it to supply oil to lifter
20. Rocker Arm u Transmit cam lobe action to the valve stem, two type adjustable and non adjustable can be mounted on shaft or a individual stud, overhead cam-rocker arm operates on camshaft (eliminates the middle man), roller rockers