Specific Components

Specific Components

Oil Pump



QUESTION : (1) What is meant by the term dry sleeve?

A dry sleeve is a replacement sleeve used to repair damaged bores in blocks. The outer surface of the sleeve makes contact with the machined cylinder block and does not form part of the water jacket. These sleeves are fitted with an interference fit of between 0.05 to 0.1 mm. (.002" to.004"). The sleeve to be used is selected from a range that has the correct inside diameter to allow for re-boring to the piston size after installation, leaving a minimum of 0.75mm (.030") wall thickness. The sleeves are longer than the bores and have to be machined within +3mm of the required finished length. The blocks are stepped bored at the bottom to locate and secure the sleeve position. The trimmed sleeve is pressed or freeze shrunk into position, surfaced level to the block face, re-bored and honed to suit. ( When fitting 1 sleeve only, the adjacent un-sleeved bore may be distorted due to the interference fit so careful measuring and honing is required to eliminate further problems.)



QUESTION : (2) What is meant by the term wet sleeve?

Wet sleeves are part of some original engine designs. The sleeve forms part of the water jacket and is sealed at the top and bottom with gaskets or o-rings. These sleeves are robust and have the advantage of replacement as a factory finished unit. (Finished piston and sleeve assembly). They have the disadvantage of failure due to coolant loss via the o-rings to the crankcase. Corrosion of the block is common where wet sleeves are part of some alloy block designs. Close inspection of sealing areas is vital.



QUESTION : (3) What are the two common materials blocks are made out of?

Cast iron or aluminum.



QUESTION : (4) What properties of a cast-iron block are superior to an alloy block?

a) Cast-iron blocks are more corrosion resistant than alloy blocks.
(b) Cast-iron blocks are generally more forgiving when overheated.
(c) Cast-iron blocks are suitable for ring contact while alloy blocks require sleeves. ( Some small stationery engines run alloy bores )



QUESTION : (5) What properties of an alloy block are superior to a cast iron block?

(a) Alloy blocks are much lighter than cast-iron blocks.
(b) Alloy blocks reach normal operating temperature quicker.
(c) Alloy blocks don't suffer from rust scale erosion as cast blocks do. (Radiator blockages are less likely).



QUESTION : (6) What is the purpose of a stress plate when boring an engine?

Most cylinder bores distort when the cylinder head is bolted to tension. If the block is bored free (without a stress plate fitted) the careful machining can be upset when the engine is assembled. This will lengthen the bed- in time of the rings. The stress plate is a flat robust plate, the same shape as the head gasket, that is tensioned into position to simulate the conditions of the assembled engine. The boring and honing procedures are carried out with this plate tensioned in place. Once removed the bores may show signs of ovality and distortion but will return to their machined finished sizes once the head is fitted.



QUESTION : (7) What is the recommended amount of material left to hone out of a bore when boring and why?

The recommended honing allowance when re-boring is 0.05mm to 0.07mm.(002" to .0025"). The reason that this amount of honing is recommended is to ensure all the boring marks are removed. The boring process leaves a rough surface similar to milling and is very unsuitable as a surface for rings to run on. A shallow hone pattern will disguise these boring marks so they are not visible with the naked eye, resulting in pre-mature ring wear. After the rings have failed the boring bar marks can be very visible in the ring travel area, even though the hone pattern completely disguised it at the time. So 0.05mm to 0.07mm (.002" to .0025") is adequate as the honing margin provided the bore finish achieved is satisfactory in the first instance.
( The required boring bar finish normally can't be achieved in one large cut. A final bore cut depth of around .005", with a correctly sharpened tool will produce the recommended bore finish ready for honing).



QUESTION : (8) What is a cross hatch pattern referring to?

The visible pattern left by correct honing methods is seen as a series of lines that cross over each other in both directions at a minimum angle of 30 degrees.



QUESTION : (9) What is unidirectional honing and what can it cause?

Unidirectional honing as the name suggest is when the normal cross hatch pattern does not exist but is a pattern predominately in one direction up the bore. It is usually caused by uneven stroke movement from up to down when honing. Worn hone heads and universal joints can also cause this problem. …it can cause ring spin.
See "Engine Problem / Block - Worn Out ."



QUESTION : (10) What is plateau honing?

Plateau honing is the name given to a honing procedure that results in maximum plateau in the hone finish. The plateau is simply the smooth section between the prominent honing marks. This can be increased by finishing the final hone procedure with finer grit stones set at lower pressure.



QUESTION : (11) What is a bottle brush or flex hone?

The bottle brush or flex hone is quite often miss-understood by the so called experts in reconditioning. Some in the industry have nicked name them dingle-berry hones. The flex hone is made as a series of honing balls around the size of peas attached to an instrument similar in shape to a bottle brush. They are produced in a series of sizes that suit different bore sizes. The flexible nylon wires that have abrasive balls attached control the stone pressure automatically. They were designed as glaze breakers for rebuilds and re-rings whenever the engine is not re-bored. They do an excellent job and are much more suitable in this instance than a rigid hone. Flex hones have been used in our workshop as the preferred honing device as a glaze breaker for over 20 years. They have performed in this role perfectly on every occasion. These flex hones by design are not suitable for stock removal when honing re-bored or reconditioned engines. However most prominent and street wise reconditioners incorporate the use of the flex hone as the final part of the honing sequence. I think the term dingle-berry is referring to those who don't understand the role of flex hones.



QUESTION : (12) What is the preferred method of honing that reduces the ring bed -in period with current design rings?

The preferred sequence we use when honing a re-bored engine is to rigid power hone using 220 grit (AN300 SERIES), removing the first .05mm (.002") of stock. Change the hone stones to 400 grit (M27J87 SERIES) and hone the remaining 0.013mm (.0005") to the finished size and acceptable crosshatch pattern. The final step is to finish the sequence with 10 strokes of a flex hone. As the flex hone removes little to no stock the finished size remains the same. With the use of good quality rings the bed in period is usually short. Some engines require a different sequence but this generally suits most engines.



QUESTION : (13) What does line boring a block describe?

The main tunnels or cam tunnels in a block have to remain straight otherwise the shaft may seize or bearings may fail. The crankshaft main caps can be closed (mating faces ground to reduce the size of the tunnel) and a line boring machine is used to re-machine the tunnel back to the original size and correct alignment. Cam tunnels in blocks don't have removable caps so the cam tunnels are machined oversize and o/s backed cam bearings fitted. This repair is limited by the availability of o/s backed cam bearings.



QUESTION : (14) When surface grinding a block face what engine assembly procedure has to be considered?

As with any surface grinding of the head face , block face or cam box face the amount machined can have an adverse effect on non- adjustable hydraulic tappets. The addition of suitable head or OHC shims can usually restore these specifications. Calculated Machining of lifter bases, rockers or valve tips is often required to rectify excess block face removal. The assembler has to establish that the lifters are within operating limits. Secondly the piston protrusion on some diesel engines may require rectification by piston crown machining. In these cases a dummy assemble and piston deck height check has to be carried out. Block dowel protrusion has to be checked to ensure clearance in the cylinder head is not impaired. Protruding dowels can prevent establishing correct clamping pressure on the head gasket. The ability to establish exact OHC timing, compression ratio and valves clipping pistons all have to be considered. With some engines these issues are not ever a problem but as engine design become more intricate these issues become more critical.



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QUESTION : 1) Name the 3 specific types of cylinder heads?

(a) Flat or side-valve.
(b) Overhead valve OHV.
(C) Overhead cam (OHC).



QUESTION : (2) Under what conditions do exhaust valves normally operate? And why do exhaust valves burn more often than inlet valves?

Exhaust valves operate in a very harsh enviroment. The temperature of an exhaust valve in a petrol engine operating under favorable conditions is around 750 to 850 degrees centigrade. As the normal combustion temperatures are around 2000 to 2500 degrees centigrade any increased combustion temperature will heat the exhaust valve to above what it was designed to operate at. Inlet valves in the same engine have the advantage of the cooling effect of the intake air. When the inlet valve is open and off its seat it is subject to cool intake air. When the exhaust valve is open and off it's seat it is subject to combustion heat. If any problem exists such as weak valve springs, tight tappets or worn guides the cooling effect that takes place as the exhaust valve is seated will be reduced and the valve will overheat and burn.



QUESTION : (3) Why do exhaust valves normally have wider tappet clearances than inlet valves?

Unlike intake valves, the exhaust valves don't have the added advantage of cooling intake air flowing over them. The exhaust valves must be given longer dwell time to dissipate their heat through the valve seat into the coolant. The correct seat pressure must be maintained and a wider tappet clearance ensures the exhaust valve is not held up off its seat during operation.



QUESTION : (4) Why do inlet valves generally have larger heads than exhaust valves?

Normally aspirated engines have the intake air entering the cylinder under vacuum conditions using the difference between negative manifold pressure and atmospheric pressure. Intake air enters the engine at low pressure and requires a larger valve to allow the required volume of air to enter the chamber during the intake stroke. The compressed combustion exhaust gas is forced out of the exhaust valve. Therefore the efficiency of the intake has to be larger than the exhaust.



QUESTION : (5) What modifications have to be carried out on the average cast-iron cylinder head when converting to LPG?

Modifications that are required will depend upon the efficiency of the particular engine in question. The average cast-iron head off a FORD, HOLDEN or CHRYSLER usually requires the fitting of hardened valve seats. The seats on most of these heads are machined directly into the cast-iron head and are not suitable for lead free fuel or LPG. As both these fuels have no lead or additives to soften the force of the valves seating, the valves soon become pounded into the head. This can happen in a very short period and tappets will continually ride quickly burning the valves.
Hardened or heavy duty exhaust valves are also required in some applications. Often if the standard valves are simply replaced with new ones at the time of the conversion a satisfactory valve life can be achieved. So new exhaust valves rather than reground are the minimum requirements.
Another modification that is helpful, is the fitting of bronze valve guides. These guides tend to be more wear resistant and while maintaining good stem clearance dissipate the valve heat better. For LPG Raise the compression if power output has to be maintained. LPG operates well with a high compression ratio. For unleaded lowering the compression can be helpful as the octane rating of regular ULP is lower than super or leaded fuel. Most ULP conversions run better on premium unleaded.



QUESTION : (6) What can valve guide wear cause?

The most obvious problem with valve guide wear is exhaust smoke. The evidence of exhaust smoke when the throttle is opened after an idling period usually indicates valve guide, stem or seal wear.
The other resultant damage from worn guides is burnt valves. As the worn guides don't guide the valve directly onto the seat but rather let it slide into position, accelerated seat wear results in burnt valves. Severe pitting of the valve face due to the carbon generated from the passage of oil down the worn guides is another common related problem.



QUESTION : (7) Why is valve spring tension important?

Valve spring tension is set by engine manafacturers at a rate that will eliminate valve bounce within the operating rev range of the engine. The spring rate in standard factory engines is set to a level that satisfies the valve bounce and seating requirements yet will not overload the valve train causing premature wear.
The correct seat pressure exerted by the spring allows the correct transfer of heat from the valve to the engine coolant. The valve spring tension at closed length and open length must be within specifications.



QUESTION : (8) Why is it important to know the nominal cylinder head thickness?

See " nominated head thickness charts" on this site.
These specifications are useful in determining the amount of stock removal from the face of the cylinder head. Some OHC heads are machined on both faces and examination has to determine which face has had excess machined from it.
The use of head shims and cambox / tower shims can restore the head to within useable thickness. As well as compression ratios being raised above safe levels, the rocker arm geometry, cam belt or chain tension can be adversely effected.
If head shims are not available some heads will be unserviceable as severe detonation will occur when the head face is excessively machined.



QUESTION : (9) What is meant by " straightening a cylinder head"?



QUESTION : (10) Why do bent OHC cylinder heads have to be straightened before they are surface ground?



QUESTION : (11) What does sencro-seating describe?

Synchro-seating is a description used when stoning valve seats. The stones are faced in the arbor they are mounted on. The use of the correct pilot grinds the seat concentric to the guide. The throating angle was ground by changing stones and the top angle required another stone change. This method required a high degree of skill, was dirty and time consuming. The preferred method today is machining the three angles (top ,seat and throat) in on operation with a multi-angle cutter and specialised machine. The only use for a synchro seating stone in modern workshops is for polishing difficult seats after machining.



QUESTION : (12) What is a cylinder head vacuum test?

A cylinder head vacuum tester is used for two purposes. One to quickly check if valves have a satisfactory seal when examining the head for repairs. This test is carried out with the valve springs still fitted and only indicates the ability of the valve to seal compression. This test used in this manner does not check the concentricity of the valve and seat or its condition as the valve spring tension will overcome minor faults. This assembled test is simply a guide to the general condition of the valve and seat and to the condition of the port. In this test a pad seals against the port face and a vacuum pump creates a vacuum in the port to the valve seat. Holes in ports can be identified before work commences on the head. The second use is to check the concentricity and conformity of newly machined valves and seats. This test is carried out without the springs fitted with the machined valve simply resting on the seat. This ensures 100% seal and extended valve life.



QUESTION : (13) What is a cylinder head crack test?Cylinder heads are crack tested using a few

different methods. Two common methods are magnetic crack testing for cast iron and dye check for alloy heads. The magnetic cracktest uses a magnetic particle fluid and magnets. The particle fluid is drawn into the crack and is highlighted under ultra violet light. An older magnetic dry powder test uses the same principal of the magnetic powder being drawn into the cracks between the magnets. This powder line is visible under normal light. The dye check method for alloy heads involves the use of a pre cleaner, a dye and a developer. The dye penetrates the crack and when the excess is hosed off and the developer is applied, the crack is visible as a highlighted line.
All heads have to be fully dismantled and cleaned before any successful crack test can be done.



QUESTION : (14) What is a cylinder head pressure test?

See "Engine Problem / Head - Hole In" A cylinder head pressure test is carried out either using hot or cold water. The method involves sealing the water ways and testing for leaks under pressure. Different machines use slightly different methods but pressure testing will find cracks as well as tiny pin holes that can be missed by crack testing. The hot pressure tester shown in this site is the most common style in use today. This tester allows hot and cold testing under varying pressures. Again the cylinder head has to be stripped bare and cleaned as the hole or crack is spotted visually while under test.



90% to 100% correct answers indicate a good understanding of engine problems and functions. This web site is full of information that may improve your knowledge and skill.




QUESTION : (1) What is the main purpose of a crankshaft in an engine?

The stroking or reciprocal movement of the piston in a cylinder is useless as a motion to power a vehicle or most machinery. The main purpose of a crankshaft is to convert the reciprocal motion into rotary motion. (Usable motion)



QUESTION : (2) What are some of the materials cranks are made from?

The common materials include,
(a) Cast iron
(b) Cast steel
(c) Forged steel
(d) Nodular iron



QUESTION : (3) What is the nodal point in a crankshaft?

The nodal point in a crankshaft is the name given to the position where a crankshaft is most likely to crack. This position is where the maximum stress and vibrations are concentrated. This point is usually towards the flywheel end and is moved whenever the weight of the balancer or flywheel is changed. A lighter flywheel will move the nodal point closer to the centre of the shaft.



QUESTION : (4) What is a fillet radii?

This is the area machined by the radius edge of the grinding wheel where the journal ends and the web starts. This machined fillet area is very important in preventing cracks and broken shafts. When grinding cranks it is extremely important to maintain the recommended manafacturers profile of this fillet radii. When straightening a shaft using punches in this area it is important to restore this radii position and remove any dints or scratches. This area is often rolled or shot penned to stress relieve the shaft.



QUESTION : (5) What two tests should be carried out before grinding a crankshaft.(especially diesel shafts)?

Crack test and a straightness test.



QUESTION : (6) What is the general minimum hardness of an non-hardened shaft measured in RC (ROCKWELL C)?

23 RC



QUESTION : (7) What is the general minimum hardness of a hardened shaft measured in RC (ROCKWELL C)?

Minimum 40 RC



QUESTION : (8) What three processes are commonly used to harden shafts?

(a) Induction hardening
(b) Nitriding
(C) Tuftriding



QUESTION : (9) What grit tape should be used to hand linish a shaft?

280 to 320 grit will give the best results



QUESTION : (10) In what direction should the shaft rotate in relation to the linishing tape when hand linishing?

The same direction as in the engine (clockwise)



QUESTION : (11) What is "linishing" trying to achieve?

Linishing is trying to remove the burrs created during the grinding process. (The wrong direction of rotation during linishing will lay the burrs down rather than remove them.)



QUESTION : (12) How is "changing the stroke" achieved when grinding a big end journal?

The big end journal can be set up "offset to center" towards BDC and ground undersize to achieve a longer stroke. If .040" undersize bearings are available an offset of .015" will achieve a.030" stroke change and still allow .005'' of grinding to clean up the journal at BDC. This change will also increase the assembled deck height of the piston by.015". Higher compression and increased swept volume is achieved in one process.



90% to 100% correct answers indicate a good understanding of engine problems and functions. This web site is full of information that may improve your knowledge and skill.




QUESTION : (1) What is the main purpose of a cam shaft?

The camshaft is designed to facilitate the opening and closing of the valves in a controlled preset manner.



QUESTION : (2) What is the cam journal?

The cam journal is the machined face that runs on the cam bearings.



QUESTION : (3) What is a cam lobe?

The cam lobe is the profile machined surface the valve lifter runs on.



QUESTION : (4) What is the base circle?

The base circle is the position on the cam lobe that is in contact with the lifter while the valves are seated.



QUESTION : (5) Where are the opening and closing ramps and what are they designed to do?

These ramps are at the commencement of the lift and at the closing of the lift, at either end of the base circle area. These ramps are designed to slow the acceleration of the opening of the valve and to slow down the closing of the valve. These ramps prevent damage to the valve train and softens the seating contact during closing to prevent valve and seat damage. See answer to question "24 of general engine questions"



QUESTION : (6) How is the valve lift governed by the camshaft?

The lift is determined by the height of the cam lobe. The difference between the base circle and the total height of the lobe will give the lift at the lobe. If you multiply this cam follower lift by the rocker arm ratio you can calculate the lift at the valve.



QUESTION : (7) What is meant by valve overlap and when does it occur?

Valve overlap refers to the position during the engine cycle when the exhaust and inlet valves are open together. This occurs at TDC on the exhaust /intake stroke. All engine have valve overlap as part of camshaft design and is demonstrated when the valves are "rocking." (Exhaust closing and inlet opening)



QUESTION : (8) What effect does increased valve overlap have on cranking compression pressure?

The compression pressure at idle and low speeds will be considerably lower as compared to that of a standard camshaft.



QUESTION : (9) What does an engine have a "lumpy" idle with a race cam?

The rough idle is the engine reacting to lower manifold vacuum and incorrect combustion. The valve overlap will determine the severity of the rough or lumpy idle. Increased valve overlap looses its bad idle characteristics as revs are increased. The overlap and extra lift will increase performance substantially at higher revs.



QUESTION : (10) What is the finishing process called that is applied on newly re-ground cam lobes (cast or non-hardened camshafts) and for what purpose?

The process is called lubriding and is a hot dip molybdenum disulphide coating to aid bed-in at initial start. The shaft lobes take on a dark gray appearance. The down side of this process for an assembler is that the lobe finish is disguised to a point where chatter or poor finish can be missed.


90% to 100% correct answers indicate a good understanding of engine problems and functions. This web site is full of information that may improve your knowledge and skill.

Oil Pump



QUESTION : (1) What 7 general components make up the lubrication system on an engine?

(1) Oil sump
(2) Oil pump
(3) Oil pump pick up and strainer
(4) Pressure relief valve
(5) Oil filter
(6) Oil pressure switch
(7) Oil gallery.



QUESTION : (2) What types of oil pump drives are commonly used?

(A) Gear driven direct from camshaft
(B) Hex drive direct from the distributor
(C) Chain drive from the crankshaft
(D) Direct drive from rear of camshaft.
(E) Direct drive from front of crankshaft.



QUESTION : (3) What 2 types of oil pumps are commonly used?

(a) Gear type
(b) Rotor type



QUESTION : (4) What is the function of a relief valve?

A relief valve is fitted to control the set maximum oil pressure. Oil pressure has to be controlled to a preset maximum to ensure oil seals, welsh plugs and filters are not damaged. Most oil pumps are capable of pumping well over 100 Lbs/sq.in. This pressure will burst most spin on oil filters and cause engine oil leaks at o rings and seals. When the engine oil is cold the higher viscosity produces higher than normal pump pressure and the relief valves opens allowing oil to by pass the gallery back to the sump. The pressure is regulated by spring tension on the relief valve.



QUESTION : (5) At what position in the lubricating system is the oil filter and oil strainer fitted?

The oil filter is fitted between the oil pump and the oil gallery prior to any bearings or components. The oil strainer is fitted on the suction side of the oil pump.



QUESTION : (6) What is meant by " by pass" and " full flow" oil filters?

(1) A by-pass system only filters a metered amount of oil and the remainder of the oil enters the engine un-filtered.
(2) The full flow system filters all the oil before it enters the oil gallery. This type of filter system must incorporate a by pass valve to allow oil to the bearings in case of a filter blockage.



QUESTION : (7) What are the three main functions of engine oil in an engine?

(a) Lubrication of all moving parts. (pistons,rings,bearings, bushes, shafts and gears)
(b) Cooling of moving parts (especially pistons and shaft bearings)
(c) To keep the engine clean (the detergent additive in oil cleans the inside of the engine and the oil carries the abrasive components and carbon to the filter)



QUESTION : (8) What does the rating letters and numbers stand for in the description of an oil.eg SF/CD 20W50?

The first letter S of SF refers to the suitability for spark ignition/petrol engines and the second letter F of SF indicates the rating of the oil. The further up the alphabet the higher the rating.
The first letter C of CD refers to the suitability for compression /diesel engines and again the second letter D of CD indicates the rating of the oil.
20w-50 indicates the viscosity rating or weight of the oil. The 20w of 20w-50 is a rating of the oil when cold and the second part 50 of 20w-50 indicates the viscosity rating of the oil when hot.



90% to 100% correct answers indicate a good understanding of engine problems and functions. This web site is full of information that may improve your knowledge and skill.

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