Total Engine Assembly
A GUIDE TO STANDARD ENGINE ASSEMBLY PROCEDURES.
Correct engine assembly procedures give your engine the best hope of good power, quiet running and a long life. Every mechanic, both qualified and un-qualified can build an engine with these qualities if they are prepared to follow set assembly procedures. More often than I would like I have found most mechanics to be poor engine assemblers simply because of attitude. I have been involved in building engines for over 35 years and continue to refine my skills and knowledge on a daily basis. As a qualified tradesman motor mechanic and experienced engine reconditioner I wish to pass some of my knowledge on to others who are interested in raising the skill level of the industry.
Engine assembly procedures are not secrets or ideas that are only possessed by race car mechanics but are a combination of engineering know how and simple common sense. The best engine assemblers are often those that trust none of the machine work or parts suppliers claims. The procedures I personally use were developed out of the philosophy that the assembler is fully responsible for any warranty problems with the engine. This means if a bearing was to fail due to a shaft being ground incorrectly the assembler would be to blame for not checking the machine work, not the engine reconditioner who ground it. A lot of mechanics may disagree and argue with this philosophy but the truth is, “the buck does stop with the assembler.” Until assemblers realise this, their assembly procedures will fall short of what is required to consistently build good quality engines.
Many assemblers have come to my employment over the years who think they know it all and with in the first hour I realise this guy needs retraining. Even though he may have come from a big reconditioner his skill level and procedures fall short of what is required to produce good quality engines. But I must confess that some others have inadvertently passed on tips and procedures that I have added to my procedures to enhance my skill level. I am for ever grateful to those who taught me to seek knowledge and use it. Hopefully I can repay the industry by sharing some of these ideas with you.
Good engine assembly relies upon a few simple principals.
(2) clearance checks.
(3) adequately lubricate all assembled parts.
(4) be aware of particular engine problems.
(5) always build with correct torque, clearance and timing specifications.
(6) don’t take any chances.
THE FINAL WASH.
The first principal requires the assembler to understand that engine reconditioners or machinists don’t final wash their machine work. Even if your machinist or reconditioner delivers your machine work wrapped in plastic, looking clean as a whistle, unless it’s assembled it has not been final washed. So the first assembly procedure is to final wash all the components that have been re-machined or are to be reused. The final wash procedure is very important and some principals and understanding is required to carry out this simple task to an acceptable level.
Firstly I will start with specific components.
The cylinder head…… most reconditioners dry bead blast their heads while some wet blast. The latter appears to produce less damage and stress to threads and cam tunnels etc. but both are acceptable methods of pre-cleaning. If the reconditioner did not remove the welsh plugs, oil gallery plugs or bypass valves these must be removed before final washing. All threads must be re-tapped and blown out. The oil gallery must be brushed and washed out. Suitable oil gallery brushes are available. Special attention must be given to cavities on the top of the head where glass bead is compacted with oil sludge. The spark plug seating area is another place a build up must be loosened or removed prior to final washing. I recommend a spin in a hot parts washer prior to the final wash.(if available) Final washing of the head and it’s components is recommended in clean kero or solvent. A little degreaser added to the solvent will ensure a better final wash. Use a big volume of water ensuring the water jackets, threads and oil passages are thoroughly flushed. Blow out all areas with compressed air giving individual attention to each threaded hole and oil gallery. If any dirt or glass bead is evident at any point when air drying the head, re- wash the head.
The block……the block has undergone a different machining procedure and requires a different final wash procedure. Again the welch plugs and oil gallery plugs have to be removed if they are not already. All threads must be tapped and checked. This also means the alternator and any accessory threaded hole. All oil galleries to be thoroughly brushed out. Usually the reconditioner has hot tanked the block (cast iron) so ensure all loose scale in the water jacket is removed. Again it is recommended that the block is put through the hot parts washer if available. Wash the block in solvent with a little degreaser. Pressure wash the water jackets and check for any welch plugs that may have been pushed into the water jacket at the time of dismantling. Now that the block is clean of oil and solvent it is time to clean the bore. The cylinder bores have to be treated differently to any other component as they must be final washed in hot, soapy water. This process is best achieved using a soft brush.(bottle type brush). The reason for using hot soapy water is that no other method removes the abrasive residue left in the hone finish on a cylinder bore. Some times the bore has to be washed several times before an acceptable standard is achieved. The method of checking this standard is to rub a clean oiled white rag up all the bores. The rag must have no trace of black hone residue before the bore can be called clean. Another area that is mistakenly neglected is the inside of the crankcase area. this area is very rough cast finished and tends to trap the honing abrasive residue. This area should also be rechecked with the white rag test to ensure a complete clean. Again the block should be blown off with air giving special attention to the tapped threads. All machined surfaces should be protected from surface rust by the application of a rust inhibitor.(e.g. RP7)
The crankshaft…… the reconditioner usually hot tanks the shaft prior to grinding so the outside of the shaft is reasonably clean. The preservative has to be removed from the journals. The best way to clean a reground crank is in a kero bath using a gallery brush to clean all drillings. Some cranks have removable oil gallery plugs, so where practicable remove to ensure no rubbish is trapped against the plug. Other cranks have aluminum gallery plugs so check they have not been damaged. (caustic hot tanks will damage these alloy plugs) The flywheel mounting boss often has to be buffed or cleaned with emery tape, as it can be rusty and overlooked by the reconditioner. The front snout may also require attention. Check that the old spigot is removed and all threads and keyways are serviceable. Inspect the oil gallery drillings and ensure they are correctly chambered. Carry out these operations before completing the final wash. Pressure wash and air dry. Spray the shaft with rust inhibitor to protect the ground journals. Care has to be taken to protect the machined surfaces at all times. Make a close inspection of the journals in case some accidental damage has occurred after grinding or linishing. If a journal has to be re-linished due to damage rewash crank again.
Setting up the engine…… This procedure when carried out correctly will eliminate a lot of interruptions during the course of assembly and also may identify some fundamental problems. A clean, well lit area with ample bench space to methodically lay out all components including nuts bolts and washers is essential. During this process of set up it is important to verify the correct engine parts have been chosen. To do this correctly the assembler has to have a good description of the engine he is assembling. Some times an engine could have been bored using the incorrect model pistons. All parts should be rechecked for their correct application. The assembler has to have the appropriate books available to check part numbers are suitably selected. A good assembler never assumes that the person before him has done his job correctly but re-inspects and checks all aspects of the reconditioning process. The person boring the engine could have been given pistons of incorrect compression ratio and even though this engine will run it may lack power or worse still ping its head off. Never assume anything, always check and become fully familiar with the engines you are assembling. Due to the fact that certain engines can be used in different models and for different applications several configurations of pistons, heads, tappet covers and sumps may be available. You would hope this has been sorted out before this stage but Murphy’s law necessitates the assembler to verify. You are the last line of defense and have a responsibility to ensure quality control is maintained.
Setting up should involve the placement and counting of every nut, bolt and washer in an order. All parts should be accounted for before any assembly is attempted. The last thing you want to be doing during assembly is wandering around looking for bits and pieces. This will only lead to frustration and the possibility of mistakes will increase.
The details of the engine you are about to assemble must be recorded in an assemblers record book. Model and engine number will normally be sufficient to identify the engine at a later date. Other important vital details will be recorded against the engine during assembly. Notes should also be recorded about any abnormal or unusual problems encountered during assembly.
Measurement and clearance checks…… The accuracy of the machining and grinding will have a big influence on the life of the reconditioned engine. Assemblers are required to ensure the components used are machined within these tolerances. Assemblers must have inside, outside and bearing micrometers to carry out this vital task. The piston to bore clearance, and big end and main vertical oil clearance should be calculated and recorded in the assemblers record book. This information will help determine the cause of a failure if it were to occur at a later date.
There are several acceptable methods to establish the clearance specifications.
Measuring the piston to bore clearance…… All the cylinder bores have to be measured for size, taper and ovality. Once you have established a bore size measure all the pistons. Measure the pistons at the correct position. Establish no damage has occurred during fitting to the rods. If a piston and rod assembly is dropped or even handled roughly the weight of the rod can enlarge the skirt at the contact point or even crack the skirt. The con rod cap has to be tensioned to specifications to the rod. When holding the rod in a vice be careful not to damage the rod or induce bend. The conrod tunnel is measured for out of round and bellmouthing. Record the inside micrometer reading as part of the calculation. Any rods found to be outside specifications should be rectified. At this point loosen the conrod nuts. All the bearing shells should be measured in the centre for thickness. Care has to be taken to ensure no bearing damage occurs. This measurement ensures all bearings were packaged correctly. This measurement should be within one or two tenths of a thousandth of an inch between each bearing shell. Record the highest reading which should be used in the vertical oil clearance calculation.Measure all the big end journals, checking for out of round and taper. Record the highest measurement and use this in your calculation. If the measurements were not within a couple of tenths of a thousands of an inch also carry out the calculation using the lowest measurement. The calculation is as simple as adding the measurement of two bearing shells to the measurement of the journal and subtracting the total from the tunnel measurement.This will give you the calculated or actual vertical oil clearance this particular engine has. If the calculation is within the book specifications record the answer in the assemblers record book. The basic procedure is the same for the mains.
Ring end gap……The next measurement is the end gap on the supplied rings. This procedure is simple enough but is of utmost importance. Care has to be taken when fitting the rings in the bore for measurement. To obtain accurate measurements the ring has to be placed very squarely in the cylinder. This is achieved by using the piston crown as a guide to push the loose ring down the bore. Simply place the ring in the bore and take the piston, facing the crown against the ring easing it down the bore until it is square. Remove the piston and measure the ring end gap with feeler strips. Check all the compression rings in this manner. Use caution when removing the loose rings. If they are removed unevenly breakage or damage could occur.
The minimum end gap is calculated using a general rule of .004 of an inch per inch of bore. (0.1 mm per 25mm of bore)This general rule is fine for bores from 2.5 inches to 4.5 inches. So a 3 inch bore should have a minimum ring gap of .012 of an inch.(0.3mm). Different ring manufacturers use nominal bore size to manufacture their rings and as pistons can vary in size from one manufacturer to another the minimum is often not achieved. Up to 50% above these specifications will usually be acceptable. It is more important not to be under the minimum clearance as ring seizure and breakage will occur as the rings heat up to normal operating temperature. If ring end gap is under minimum and piston to bore clearance is correct the rings should be replaced or the end gaps filed to size.
Oil rail end gap…… The easiest way to check these is to place all the rails together in the bore with all the end gaps lined up. Use a feeler gauge to align the end gaps. Anywhere between .040″ (1mm) and .070″ (1.75mm) is acceptable.
Ring back clearance…… Whenever rings are procured from different manufacturers than the pistons some differences can occur. The easiest way to do a quick check of ring back clearance is to place the ring backwards in the ring groove and visually confirm that it is below the ring land outer edge. This method allows this check to be carried out before fitting the rings to the pistons. It is a safe practice once the rings are fitted to the pistons to recheck with a small straight edge.
Fitting the cam bearings and camshaft…… Measure the camshaft journals as many shafts have the journals ground undersize. Check you were supplied the correct size. Fitting cam bearings in an engine blocks requires special tools. Unfortunately the design of most fitting kits leaves a lot to be desired. Care has to be taken to ensure once fitted the bearings still have the desired clearance and finish. Always spend time inspecting the block for marks or burrs where the bearings mount. Oil up the cam tunnel before trying to fit a bearing. These bearings rely on an interference fit to retain their position so they will show some resistance when fitting. Also spend time lining up the correct bearing to the correct journal as most are of a progressive size. The oil feed holes have to be aligned by eye. Use a piece of alloy welding wire as a guide by placing it down the crank tunnel drilling that goes to the cam shaft bearing. Some front bearings have more than 1 feed hole. Be careful to ensure the bearing is around the correct way aligning both feed holes. Once the bearings are in place, oil the bearing from the crank drilling. Carefully fit the camshaft in the block. Care has to be taken not to mark the bearings as the camshaft is inserted. The camshaft must turn freely by hand otherwise serious camshaft damage will occur on start up.
Fitting Welsh plugs and oil gallery plugs…… selection of Welsh plugs will depend upon the application. Diesel engines should use stainless steel as erosion seems to be more prominent than in petrol engines. Brass Welsh plugs are a good choice for most applications. The life of plain steel Welsh plugs will depend upon the quality of the Welsh plug and the maintenance of the inhibitor at the correct levels.
When fitting Welsh plugs ensure the block is not damaged. Emery finish the Welsh plug hole if minor damage or foreign material is evident.(hard sealer or rust etc). Use a suitable sealer such as aviation gasket goo. When fitting saucer type Welsh plugs such as the camshaft plug in some V8’s.use a solid flat punch to flatten 2/3’s of the dome area in the centre only. Don’t reshape from convex to concave, just go to flat as at this point maximum size and sealing pressure has been achieved. Don’t use the ball of a hammer to butcher the plug into submission as the quality of the seal will be suspect. SIMPLY NEATLY FLATTEN 2/3’S OF THE DOME AREA IN THE CENTRE, STAYING AWAY FROM THE SEALING EDGE.
Fitting cup Welsh plugs…… Special tools are available to fit cup Welsh plugs. These may be OK, but I have no faith in them. These tools rely upon contact with the outer edge or sealing area of the plug. If you look at a modern style cup welsh plug you will notice that the sealing ring is only around 1 to 2 mm wide on the very outer edge. Any slight burr or mark on a tool that contacts the sealing edge will result in a coolant leak. These fitting tools may be OK while brand new but I prefer to use a good internal fitting tool. My advice is to never fit welsh plugs using the sealing outer edge. Select a tool that has around 0.5mm. clearance on the inside of the cup. Use a good quality sealant. Squarely and firmly hammer the welsh plug to flush with the inner edge of the fitting chamfer. This method has been reliable and has had 100% success against leaks over a 25 year period.
Threaded welsh or gallery plugs…… These are very easily sealed with a good sealant. Don’t use thread tape.
Fit the crankshaft….. Ensure the main tunnels are dry and clean. Mount the main bearing shells ensuring the uppers are fitted to the block and the lowers to the caps. Fit the thrust bearings to the cap and tunnel using a smear of petroleum jelly to secure them in position.(if separate thrusts) Ensure the bearing material of the thrusts is facing the crankshaft. Oil the mains and place the shaft in the block. Fit the main caps. Lightly oil the threads on the main bolts and oil the contact area on the bolt head and tension to specifications. Rotate the crankshaft and check for free rotation. Any binding at all will indicate a problem. The shaft should be able to be spun by hand and continue to rotate under its own weight. Anything short of this result means a problem exists with the straightness of the shaft or main tunnels.
Dial gauge the end thrust of the shaft and ensure it is within tolerances. A general rule for minimum thrust clearance is as simple as dividing the shaft main journal diameter by 450. The answer is correct using metric or imperial measurements. The general rule for maximum thrust clearance is to divide the shaft main journal size by 350. Anything outside these limits should be corrected by re-grinding and fitting oversize thrusts or a replacement crankshaft.
If rotating the shaft a tight spot or binding occurs, remove the crank and check for witness marks on the main shells. Recheck tunnel straightness, crank straightness, main tunnel size, bearing thickness, main journal size, damaged journal or dirty assembly. If the crank spins freely and the thrust clearance is within limit the crank could be left in place and the rear main seal mounted. If a wick type rear main seal remove the shaft and fit the wick seal. Fitting the rear main seal prior to this would have inhibited the ability to verify a freely rotating shaft. Once the rear main is fitted replace the shaft again rotating the shaft to check the seal drag. Sometimes the wick seal may need to be re-worked again before the seal drag is acceptable. When the shaft can be rotated by hand without the aid of a spanner (simply by holding on to the crank web) the wick seal is considered to have the correct drag. With the crank fitted extra oil is to be directed beside the main caps and down the rear seal oil relief to ensure good lubrication on start up. Rear wick seals can pick up and turn or just simply burn if this procedure is neglected.
Fitting rings to pistons…… the most common mistake made when fitting rings to pistons is to fit the compression rings upside down. The standard rule I learnt as an apprentice was “inner chamfer upward, outer chamfer down, unless otherwise marked.” On most occasions this rule will be correct. Almost all rings that the chamfer rule can’t be applied to will have a mark that goes upwards. Always read the manufacturers instructions if available.
As an assembler it is wise to learn what type of ring designs are available and what materials they are made out of. This information can assist you to choose the most appropriate ring for the engine you are assembling. As an example, a top compression ring that has an outer chamfer or bevel and is marked to have the bevel upwards is very obviously used in re-rings and would not be the best choice for a reconditioned engine. (called a “ridge dodger ring”). Like wise a chromium plated top compression ring would be a poor choice for a re-ring as it may never bed in.
Fitting the oil ring: There are two basic types of oil rings, cast iron and segmented. The cast iron oil ring comes in various designs. Some cast iron oil rings rely on a small coil spring slotted into the rear of the ring to hold tension against the cylinder wall. Segmented oil rings come in two basic designs. The three piece, two rails and an expander being the most common. The other is called a unitised oil ring. This style has two rails separated by a spacer and uses a sinewave expander. Fitting the three piece segmented oil ring is as simple as placing the expander in the groove, ensuring the ends do not overlap (butt together only). Now wind in the upper rail leaving the gap 90 degrees from the expander join. Next, wind in the lower rail leaving the ends 180 degrees from the upper rail ends. Recheck that the expander has not overlapped. Take your thumb and third fingers on opposite sides of the assembled oil ring and move the ring around in the groove as a unit. The correct feel is free, but not loose or sticky.
Fitting the compression rings: Compression rings can not be wound into the grooves. Even if they don’t break this will damage them. Compression rings should be opened at the ends just enough to allow them to be placed over the piston into the grooves. The gaps should be placed opposite, but in service they may move and even line up. This does not cause any concern.(contrary to the popular myth) The ends can be opened with your thumbs, while supporting the rings with your fingers. Lower the compression ring into its groove. It is easier to use a ring fitting tool. Always recheck the correct location and that the rings are the right way up after fitting. A 30 second inspection will ensure no mistakes are left unrectified.
Fitting pistons in the bores…… check that the rods fall under their own weight.( don’t let the rod contact the piston skirt ) If press fit rods don’t fall under their own weight, don’t fit them as they have been assembled incorrectly. Repair before fitting as tight pin bosses can seize up on start up. Before fitting the pistons and rods in the bores mount all the big-end shells. The big end shells and con rod tunnels should be dry and clean. The most common mistake made at this point is to damage the big-end journal with the thread of the big-end bolts as the pistons are fitted in the bores. To guard against this care has to be taken to ensure the thread of the big-end bolt does not contact the shaft on the way-down. One method is to hold the big-end bolts with one hand while the piston is pushed down the bore with the other. With some engines this is hard to do so the use of rod bolt protectors is the preferred method. These protectors are simply a couple of pieces of plastic tubing around 50mm long that fit snugly over the threads. Ring compressors come in a few different designs. The most versatile are the ring clamps using the ratchet compressor pliers. Select a ring compressor that is of good quality. The more trouble you have starting the rings in the bore the higher chance you have of damaging the rings. Oil all the cylinder bores and the big end bearing shells. Oil all the piston pin bosses. Oil all the rings, moving them back and forth in the ring lands to ensure complete lubrication. Make sure the big end is on B.D.C. Clamp the ring compressor firmly and squarely onto the piston. Have the compressor positioned so as to cover about 12mm below the oil ring. Position the piston in the bore with the front mark aligned. Square up the compressor against the block face. Tap the top of the piston with a suitable tool, a soft hammer handle is best as the weight of the hammer head allows you to control the pressure placed on the rings as they enter the bore. When the top compression ring enters the bore stop tapping with the hammer handle. Remove the compressor and take hold of the big end bolts so as to guide the rod into place on the big- end journal. DON’T KNOCK THE PISTON THE REST OF THE WAY DOWN THE BORE WITH THE HAMMER HANDLE…… Use a smooth pushing motion until the rod is positioned on the journal. The reasons for doing this instead of roughly knocking the piston to the bottom is quite simple. If you encountered a problem as the rings entered the bore(such as lapped over expander or the like) bashing the piston home with a hammer is not going to alert you to any problem. By the time you realise there is a problem the bore will be damaged and the job ruined. Once you smoothly push the piston down the bore you will realise how rough it is doing it the other way. You will also be very confident of correctly fitted rings, correct ring pressure, free running pistons and never be caught out damaging a bore. Any problem you may be able to think of will be noticeable once you experience the correct feel of a piston traveling down the bore. As an example imagine the machinist damaged the bore leaving a small high spot on the lower edge of the bore. If you are pushing the piston down the bore, opposed to knocking it down you will be made aware of the tight spot as soon as the piston skirt contacts the damaged area. Knocking it down would eliminate any hope of you finding and repairing that fault and the piston could pick up in service causing an expensive warranty.
Fitting the big-ends…… Ensure the conrod tunnels are dry and clean. Mount the conrod bearing shells ensuring the uppers are fitted to the rods and the lowers to the caps. Oil the big-end cap bearing . Check the big end cap is fitted the right way around and tension the big-ends to the correct specifications. Once tensioned, DON’T ROTATE THE ENGINE BEFORE CHECKING that the rod has the correct side clearance. It is very important that side clearance is checked in the correct manner as this is a multi-purpose test. The correct method is simply to move the rod side-ways across the journal. What you are checking when doing this test is more complex than it first appears. Firstly you are checking minimum vertical oil clearance, secondly you are checking rod alignment, thirdly you are checking if you damaged the journal while fitting the piston down the bores and finally you are checking the conrod side clearance……If the rod is hard to move sideways at first, but after a small tap it seems to free up and eventually freely moves back and forth, don’t turn the engine over as most probably the journal has a ding or burr. Once you tapped the rod sideways the burr gouged out the soft bearing material and now it moves freely from side to side. If you were to turn the engine over the same burr would gouge a mark deep into the new bearings…… Remove the cap. Push the rod back up the bore far enough to be able to repair the shaft and check the bearing. Be very careful not to contaminate the engine with abrasive grit if linishing tape is used. It is better to remove and repair the shaft out of the engine. Re-fit and re-check…… For all of those four items to be correct the rod should FREELY RATTLE BACK AND FORTH ACROSS THE JOURNAL ON THE FIRST ATTEMPT. IF OK ROTATE THE ENGINE ONE REVOLUTION CHECKING THE DRAG. WHEN ALL PISTONS ARE FITTED THE ENGINE MUST TURN FREELY. IF YOU ROTATE THE ENGINE AFTER EVERY PISTON IS FITTED ANY PROBLEMS WILL BE EASILY IDENTIFIED TO THE CYLINDER LAST FITTED.
Piston deck height…… Always check piston protrusion or recession when fitting pistons to any engine, petrol or diesel. Diesel engines rely on the correct piston deck height to achieve the compression required for correct combustion. So a dummy fit is required so the piston crowns or block face can be machined to suit. Also liner protrusion is important. Cylinder head gasket thickness is also an issue with some diesels.
Assembling the oil pump…… one of the most important components in an engine is the oil pressure relief valve. The valve and housing should be linished until the valve freely rattles back and forth. Always understand the operation of the particular valve so it is fitted on the correct side of the spring. The oil by pass valve should be inspected and replaced if necessary. Some engines have a ball valve fitted to the block. It is very important that this valve is sealing as the long term life of the engine depends upon all the oil being filtered before re- entering the oil galley. It is necessary to dismantle new oil pumps as they often have machining swarf left in them. They also should be primed using a mixture of petroleum jelly and engine oil in the gear housing. Use only enough petroleum jelly so the pump can still be freely rotated by hand. Don’t use grease as the melting point is too high. In the case of a flanged pickup that is bolted to the block or oil pump housing it is important that the straightness of the flange is checked and re- machined if necessary.
Cylinder head assembly…… Modern engines are basically the same in the bottom end as they were 50 years ago. The advancement has been in the cylinder head area. Current cylinder head design has been pushed ahead because of the requirements to meet stricter pollution and economy levels. Also the public’s increasing appetite for faster and more powerful cars has prompted the car manufacturers to compete for sales using sophisticated engine design as the main weapon. The designs are also leaning more towards cam belt driven, shim adjustable, multi- camshaft heads. Even with the complex designs used today all the basic assembly procedures still apply. ( THEY ARE ACTUALLY BECOMING MORE IMPORTANT AS THE NEW HEADS ARE LESS FORGIVING.) Final wash cleanliness is critical to satisfactory cylinder head operation.
Shim adjustable tappets require dummy assembly to establish a starting point for the shim adjustment. Keep in mind that the clearance can change slightly once the final assembly takes place with the valve springs fitted. Quite often the clearance opens up as the cam is pushed upwards by valve spring tension. The amount of change will vary according to the wear factor between the cam journal and the cam tunnel. Recheck clearances after final assembly.
Lubrication of the valve guides to stem on any head is very important. The best way of ensuring good coverage of oil in the guide when assembling is to firstly oil down the guide, then oil the valve stem, place the valve in the guide holding one finger lightly over the seal end of the guide, push the valve nearly to the end of the guide working it back and forth a couple of times. Until you are sure of your technique remove the valve and visibly check with a light that you got 100% coverage in the guide. Remember valve guides are not pressure fed and are normally fitted with a positive seal to prevent oil entering the guide. So the only oil that will prevent that guide wearing or seizing is your assembly oil.All heads should be vacuum tested to check valve/ seat seal. Carry this test out with a dry clean head before fitting valve springs. If springs have to be fitted before a satisfactory vacuum test is achieved the valves and seats are not concentric. ( the seats should be syncro- seated or re- cut) The engine will run OK, but the guide and valve face life will be drastically reduced. Valve springs should be tested before re- use. All seat and valve heights should be within specifications. Diesel engines rely upon correct valve height to maintain the correct compression.
Fitting the cylinder head…… the most important gasket in an engine is the head gasket. Warranty research data shows that head gasket problems are the most common warranty claims. Due to the extreme environment a head gasket works under, it is very important to get it right the first time. Maintaining the correct clamping pressure between the head and block is the most important factor from preventing head gasket failure.
Always check that the gasket being used is of good quality and suitable for the correct application. Some diesels have different thickness gaskets and will not perform if the wrong gasket is selected. Make sure the mating faces are dry and clean of oil residue. Verify that the gasket is being fitted the correct way up. If it is ohc the engine should be on tdc and the camshaft positioned in the head to correspond, before being fitted to the block. If the cam timing is incorrect the open valves could be bent as the head is being tensioned down. Place head gasket on the block face using the block dowels to locate the gasket. Check the position of the oil feed hole. Check the coverage of the waterways. Check the position of the combustion sealing ring in relation to the cylinder bores. Ensure the sealing ring of gasket doesn’t protrude past the cylinder bores. Place the cylinder head on the block being careful not to contact the face with the block dowels. Check head studs for stretch as some of these “tension to yield” head studs have to be replaced. Lightly oil the threads on the head studs or seal the threads if it is required by the manufacturer. Lubricate the contact area of the head stud. Torque the head studs to the correct tension using a minimum of three stages, working outwards in a staggered pattern from the centre.( some heads have a special sequence, especially any with two different size bolts or three rows of bolts. Always check manufacturers spec. if not sure.)
Adjustable tappets should be accurately adjusted to .001″ (.025mm) above book clearance. This ensures no tappets will be under minimum clearance during the first 800 kms. At the first service (800 km) the tappets should be re-adjusted.
Camshaft belts and timing chains…… As there are no two engines the same in this area it is impossible to generalise with this aspect of engine assembly. The best advise is to make sure you have read the workshop manual or www.engineproblem.com.au timing belt specification section. Ensure you are very familiar with the engine you are assembling. In most cases of reconditioning very few parts can be re-used and complete timing kits should be fitted.
Always be fully aware of the timing settings as some engines have balance shafts using the oil pump gears as part of the timing procedure. Due to the complexity of modern engines in this area I always suggest when assembling an unfamiliar engine.. read the manual first. Correct belt tensions are very important. Always rotate engine at least 3 revolutions after assembly of belts or chains. Finally double check timing marks and belt tensions before covers or timing cases are fitted.
Paint and protect from dust and water…… always paint the engine in a professional manner leaving all machined surfaces clean and free from paint. (e.g. manifold, water pump, crank snout and flywheel mounting flange,etc,etc.) **Finally seal the engine against dust and water using plastic wrap or plugs.**
Footnote: Remember that the assembled engine may sit for many weeks or even months before an initial start up.
This makes your assembly lubrication of all bearing surfaces, thrust areas, pistons, rings, pins, gears, chains, cam lobes and valve train components of utmost importance. As a general rule any good quality engine oil of correct specifications is acceptable with the additional protection of assembly lube on heavy load areas such as cam lobes and lifters.
(The assembly lubrication has to be available for use until the engine obtains full oil lubrication from the oil pump. Engines can seize or scuff bearing or load surfaces during the priming procedure if insufficient lubrication was used during assembly.)
IRRESPECTIVE OF HOW WELL YOU MAY LUBRICATE DURING ASSEMBLY DAMAGE WILL OCCUR IF THE ENGINE IS FIRED UP WITHOUT FIRSTLY GAINING OIL PRESSURE.
The safest method to obtain initial oil pressure is with the use of a pressure primer connected to the oil gallery while slowly cranking the engine. ………. The engine must never be fired up without firstly gaining oil pressure.
If the engine has been assembled with the correct clearances, correct machine finishes and assembled with the correct amount of lubricant in all of the right places it is quite safe to obtain oil pressure at cranking speed with the sparkplugs removed. It is important to keep this procedure as short as possible as excessive cranking will reduce the effectiveness of the assembly lubricant. The pre-filled oil filter should be left loose so trapped air can quickly be dispelled, re-tighten when oil pressure is obtained. Some assemblers may still experience failures using this method simply because the correct assembly procedures were not used.
(No clearance checks with insufficient vertical oil clearance, incorrect machine finishing, insufficient lubrication on assembly etc. etc.)
: Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2020 UMR Engines www.engineproblem.com.au