General chat talk
10-03-2005, 05:50 PM
#1
garibaldi
Thread Starter
General chat talk
CON ROD TECH TIPS
LONG RODS
The BDA and 1.6 x-flow engines normally use a 125.2mm con rod with a 44.75mm compression height on the pistonwhich works fine for most applications. However when a high revving competition application is required improvements can be made. By using a long rod (132.8mm length) and a short compression piston height ogf 37.2mm, the piston crown will remain in the same position. By changing these lengths you gain 2 advantages. First the piston is smaller but lighter making it easier to accelerate and deaccelerate during a stroke. Secondly there is less angular movement of the con rod duriong a crank revolution approx 1.8 degrees which equates to around 10.5% reduction. Both eof these advantages result in a freer revving engine.
NARROW JOURNALS
Con rods for BDA, lotus twin cam and x-flow are offered in wide or narrow journal types. Wide journal refers to the width of the big end journal on the con rod being made to the same width as the standard con rod, ie 26.85mm. As an alternative narrow journal rods are also available where the nig end journakl has been reduced to the width of 23.7mm. This givesthe advantages of less rotating mass in the engine, less friction on the big end bearings (as this is narrower) andless drag from oil within the crankcase since the narrow rod will pass through the il with less resistance. In order to use such rods a narrow journal crank must aslo be purchased!
-----------------------------------------------------------------------------------------------
OVERSIZED MAIN BEARING HOUSINGS
Ford haveon too many occasions manufactured engines that haveoversized bearing housings in an effort to reduce the amount of scrapped blocks. Such blocks can however create a nightmare when rebuilding if you do not realise that the block requires special bearings. The result of building an engine with the incorrect bearings is little or no oil pressure and an engine that will be lucky to get a cra around the block beforebeing wrecked. The rule of thumb here is to always check to see what bearings are fitted and never assume. Also always pre-assemble using plasticgauge which will highlight any clearance problems. The engines to llok out for and the relevant measurements of the main beraing housing diameter are
STANDARD HOUSING OVERSIZED HOUSING
CVH 62.287MM-62.308MM 62.687-62.709MM
ESSEX 67.701MM-67.721MM 68.082-68.102MM
X-FLOW 57.683MM-57.696MM 58.064-58.077MM
-----------------------------------------------------------------------------------------------
PISTONS
To reduce piston slap, many pistons have a pin which is offset to the left when viewed from the front. Although all piston crowns are marked accordingly these markings can be inadvertantly removed by additional maching processes. Offset oin pistons fitted ncorrectly will result in mechanical noise and reduced inefficiency. Race pistons defer almost exclusively to a central pin design-a necessity for engine speeds over 10000rpm.
HOW TO MEASURE PISTON SIZES
When measuring pistons to ascertain there bore size, it is essential that they rae measured in the correct place. Pistons are smaller and round at the top but larger and oval at the bottom. You can measure a variance over 0.5mm depending on where it is measured. The correct position is across the skirt of the piston at 90 degress to the gudgeon pin. Also remember that the bores size will be fractionally larger due to the piston clearnce. This can be anything from around 0.02-0.1mm depending on the type of piston.
-----------------------------------------------------------------------------------------------
TIMING BELT PROFILES AND FITTING
The first generation of belt used a straight sided trapeziodial tooth form. Themuch stronger semi-circular formally initially in 8mm pitch is now widely used in a 9.5mm pitch version. Manufacturers develop shapes to improve strength and quietness. Many but NOT ALL are compatible with OE gears so cars is required.
To avoid premature failure the following list should be carried out-
1 ENSURE PULLEYS CLEAN, UNDAMAGED AND UNWORN
2 DO NOT USE A BELT THAT HAS BEEN CRIMPED DURING PACKAGING
3 CHECK THAT TOOTH PROFILE ON BELT MATCHES PULLLEY
4 CHECK TENSIONING JOCKEY WHEEL AND REPLACE IF WORN OR DAMAGED
5. TAKE TIME TO TENSION BELT CORRECTLY AND RE CHECK AFTER 500 MILES
6. REPLACE BELT AT MANUFACTURERS RECOMMENDED INTERVALS.
-----------------------------------------------------------------------------------------------
OIL PRESSURE PROBLEMS
Low or no oil pressure problems form the basis of numerous techincal questions every year. There are numerous likely causes. Before these are described you should be aware that an oil pump does not produce pressure, it produces flow. So, provided the oil pump internals have not worn out excesively then it will be able to produce the flow of oil which it was designed. It is the resistance of the oil galleries in the engine and the size of the clearance between the bearings and crankshaft journals that crate pressure in the oil. Therefore replacing an engines oil pump when the cause of low oil pressure is for example due to excessive clearance between worn crank bearings and journals, will not cure the problem.Always find the cause of the problem before attemting to fix it.
Before attemting to cure a lack of oil pressure are you sure you have a problem? A faulty oil pressure switch may illuminate the warning light so always check with an oil pressure gauge.
OK, assuming that the oil pressure has been measured and is low, does the engine have enough oil in it? Daft thing to ask but is is the first thing to check. A classic problem can occur when a new engine is made up of parts from various sources resulting in the wrong length of dipstick being used. If the oil level is correct is it the correct grade? 0w40 oil for example in a CVH engine wont do it any favours at all. Alternatively if the oi is getting too thin at high temps, then you need to investigate using either a higher viscosity oil and or an oil cooler if one is not already fitted. Has the oil filter been changed on a regular basis? Since its job is to filter impurities from the oil, it gradually fills with debris that will restrict oil flow. If left well beyond its service life it will significantly redice the engines oil pressure.
There are 3 general faults that you tend to get with an oil pump. Firstly if the pumps internals have worn so that the clearances are greater than the maximum alllowed, this will reduce the flow and pressure of oil. Any dirt that is sucked into the pump will accelerate the wear rate of the pump, particulary if the size of theimpurities are greater than the clearances within the pump. Large particles will sginificantly score or in the worst cases jam the pump. Such dirt is allowed to enter the oil pump since it is not filtered, the oil is only filtered after leaving the pump. The metal screen mesh that covers the oil-pivk up pipe only prevents very large particles from entering the pump. Any dirt within the sump is therefore free to enter the pump provided it is smaller than the holes in the screen. Anything larger ha a nasty habit of blocking the screen and reducing the flow of oil to the pump. The second and third faults concern the pressure relief valve jamming. Dirt inside the pump can easily jam the pressure relief valve. Jammed inthe open position will cause a loss of pressure and in the closed position will cause excessive pressure.
When installing an oil pump, never use sealants between faces or gaskets. When tightened the sealant will seep out and usually bits of sealant soon break free either inside the pump or sump ready to jam the relief valve. A bit of grease on the gaskets is usually all that is needed. Low oil pressure can also be a result of air being drawn into the pump. Apart from low oil level this may also be caised by too much oil-(the oil will aerate if in constant contact with the moving parts such as the crank), a leaking pick-up pipe, or even a pick-up pipe that is not posistioned at the correct level in the sump. Race engines can also suffer from low-sump oil if the oil does not drain back into the sump at the sam rate at which it is pumped back into the engine. A number of mistakes can also be made during an engine rebuild which result in low oil pressure. Not only should the crank be checked for size against the bearings fitted but also the size of the main bearing housing in the block. Some engines can use bearings that are oversized on their outside diameter.If new camshaft or jackshaft bearings have been fitted ar ethe oil feed holes in the bearings lined up with the holes on the block. Also if any gallery bungs have been moved have they been replaced. On some engines if certain oil bungs are missing the oil can escape behind an engine cover and return the oil back to the pump without any signsof leakage. And finally when installing an oil pump, always read the instructions!!!
CYLINDER HEAD AND GASKETS
To ensure minimum distortion wait for the engine to o cool down before removing the head bolts (4-2 turns a time) in the sequence as per manufacturer instructions. Thoroughly clean the head and block faces and check for true. Clean out all the thread holes in the block- use a drill or blast out with compreesed air. Check the new head gasket-is it correct? Check that the gasket fire ring is not smaller that the cylinder bore -gasket protrusion into the combustion chamber will resultin premature failure.
Some head gaskets are marked TOP or FRONT to ensure correct orinetation when fitted. Most modern composite type gaskets have special coatings and are designed to be fitted dry. A suitable selant may be rquired for some applications-check fitting instructions or with supplier. NOTE-OF CAUTION! Enlarging gasket water way holes willnot improve cooling efficiency. The size, number and position of these holes has been finley calculated by the engine and gasket designers and any alteration may propagate localised overheating and premature engine failure.
Clean and check all cylinder head studs, nuts and bolts-replace if there is any sign of wear, stretch or damage. Most modern engines use stretch bolts and these should ALWAYS be renewed. When refittingthe cylinder head it is recommended that the bolt threads are lightly oiled and installed finger tight ( a light smear of anti-seize compound under bolthead to ease friction during the torquing process is good practice).
Many cylinder heads can be successfully secured using a method of gradual tightening (in incrementsof 20lb/ft) in the sequencd recommended by manuafacturer. However most modern engines employ stretch bolts and these must be tightened in STRICT accordance. Re-torqing conventional cylinder head studs or bolts after an initial engine run is recommended. Always allow aluminium heads to cool completely before carrying out this process.
-----------------------------------------------------------------------------------------------
SPARK PLUGS
How would you like to be shut in a chamber with petrol and given a 30,000 volt electric shock, 25 times a second and be subjected to pressures 50 times greater than normal atmosphere? No?- Well thats what happens to you spark plugs! So, if you want peak performance from your engine make sure you fit suitable plugs.
3 main points to consider are:
1. All modern engines are now fitted with resistor type plugs and you are advised to stick with this type. The high energy bursts from plugs can cause interference to ICE ,EFI and engine management systems if resistor plugs are not fitted.
2. Plug heat range-many plug manufacturers produce a competition range which are usually harder or colder than the standard fitment. For mild tuning it is best to stick with the factorry recommended item but colder plugs will be necessary for seriously modidfied engines.
3. Electrode gap- unless there is a known benefit for doing otherwise, the advice is is to set up the gap. Some uprated ignition systems can generate a spark across a wider gap which may improve combustion. However on highboost turbo engines a large plug gap may result in the spark being blown out and for these engines a reduction in the gap is usually specicfied , eg Cosworth.
LONG RODS
The BDA and 1.6 x-flow engines normally use a 125.2mm con rod with a 44.75mm compression height on the pistonwhich works fine for most applications. However when a high revving competition application is required improvements can be made. By using a long rod (132.8mm length) and a short compression piston height ogf 37.2mm, the piston crown will remain in the same position. By changing these lengths you gain 2 advantages. First the piston is smaller but lighter making it easier to accelerate and deaccelerate during a stroke. Secondly there is less angular movement of the con rod duriong a crank revolution approx 1.8 degrees which equates to around 10.5% reduction. Both eof these advantages result in a freer revving engine.
NARROW JOURNALS
Con rods for BDA, lotus twin cam and x-flow are offered in wide or narrow journal types. Wide journal refers to the width of the big end journal on the con rod being made to the same width as the standard con rod, ie 26.85mm. As an alternative narrow journal rods are also available where the nig end journakl has been reduced to the width of 23.7mm. This givesthe advantages of less rotating mass in the engine, less friction on the big end bearings (as this is narrower) andless drag from oil within the crankcase since the narrow rod will pass through the il with less resistance. In order to use such rods a narrow journal crank must aslo be purchased!
-----------------------------------------------------------------------------------------------
OVERSIZED MAIN BEARING HOUSINGS
Ford haveon too many occasions manufactured engines that haveoversized bearing housings in an effort to reduce the amount of scrapped blocks. Such blocks can however create a nightmare when rebuilding if you do not realise that the block requires special bearings. The result of building an engine with the incorrect bearings is little or no oil pressure and an engine that will be lucky to get a cra around the block beforebeing wrecked. The rule of thumb here is to always check to see what bearings are fitted and never assume. Also always pre-assemble using plasticgauge which will highlight any clearance problems. The engines to llok out for and the relevant measurements of the main beraing housing diameter are
STANDARD HOUSING OVERSIZED HOUSING
CVH 62.287MM-62.308MM 62.687-62.709MM
ESSEX 67.701MM-67.721MM 68.082-68.102MM
X-FLOW 57.683MM-57.696MM 58.064-58.077MM
-----------------------------------------------------------------------------------------------
PISTONS
To reduce piston slap, many pistons have a pin which is offset to the left when viewed from the front. Although all piston crowns are marked accordingly these markings can be inadvertantly removed by additional maching processes. Offset oin pistons fitted ncorrectly will result in mechanical noise and reduced inefficiency. Race pistons defer almost exclusively to a central pin design-a necessity for engine speeds over 10000rpm.
HOW TO MEASURE PISTON SIZES
When measuring pistons to ascertain there bore size, it is essential that they rae measured in the correct place. Pistons are smaller and round at the top but larger and oval at the bottom. You can measure a variance over 0.5mm depending on where it is measured. The correct position is across the skirt of the piston at 90 degress to the gudgeon pin. Also remember that the bores size will be fractionally larger due to the piston clearnce. This can be anything from around 0.02-0.1mm depending on the type of piston.
-----------------------------------------------------------------------------------------------
TIMING BELT PROFILES AND FITTING
The first generation of belt used a straight sided trapeziodial tooth form. Themuch stronger semi-circular formally initially in 8mm pitch is now widely used in a 9.5mm pitch version. Manufacturers develop shapes to improve strength and quietness. Many but NOT ALL are compatible with OE gears so cars is required.
To avoid premature failure the following list should be carried out-
1 ENSURE PULLEYS CLEAN, UNDAMAGED AND UNWORN
2 DO NOT USE A BELT THAT HAS BEEN CRIMPED DURING PACKAGING
3 CHECK THAT TOOTH PROFILE ON BELT MATCHES PULLLEY
4 CHECK TENSIONING JOCKEY WHEEL AND REPLACE IF WORN OR DAMAGED
5. TAKE TIME TO TENSION BELT CORRECTLY AND RE CHECK AFTER 500 MILES
6. REPLACE BELT AT MANUFACTURERS RECOMMENDED INTERVALS.
-----------------------------------------------------------------------------------------------
OIL PRESSURE PROBLEMS
Low or no oil pressure problems form the basis of numerous techincal questions every year. There are numerous likely causes. Before these are described you should be aware that an oil pump does not produce pressure, it produces flow. So, provided the oil pump internals have not worn out excesively then it will be able to produce the flow of oil which it was designed. It is the resistance of the oil galleries in the engine and the size of the clearance between the bearings and crankshaft journals that crate pressure in the oil. Therefore replacing an engines oil pump when the cause of low oil pressure is for example due to excessive clearance between worn crank bearings and journals, will not cure the problem.Always find the cause of the problem before attemting to fix it.
Before attemting to cure a lack of oil pressure are you sure you have a problem? A faulty oil pressure switch may illuminate the warning light so always check with an oil pressure gauge.
OK, assuming that the oil pressure has been measured and is low, does the engine have enough oil in it? Daft thing to ask but is is the first thing to check. A classic problem can occur when a new engine is made up of parts from various sources resulting in the wrong length of dipstick being used. If the oil level is correct is it the correct grade? 0w40 oil for example in a CVH engine wont do it any favours at all. Alternatively if the oi is getting too thin at high temps, then you need to investigate using either a higher viscosity oil and or an oil cooler if one is not already fitted. Has the oil filter been changed on a regular basis? Since its job is to filter impurities from the oil, it gradually fills with debris that will restrict oil flow. If left well beyond its service life it will significantly redice the engines oil pressure.
There are 3 general faults that you tend to get with an oil pump. Firstly if the pumps internals have worn so that the clearances are greater than the maximum alllowed, this will reduce the flow and pressure of oil. Any dirt that is sucked into the pump will accelerate the wear rate of the pump, particulary if the size of theimpurities are greater than the clearances within the pump. Large particles will sginificantly score or in the worst cases jam the pump. Such dirt is allowed to enter the oil pump since it is not filtered, the oil is only filtered after leaving the pump. The metal screen mesh that covers the oil-pivk up pipe only prevents very large particles from entering the pump. Any dirt within the sump is therefore free to enter the pump provided it is smaller than the holes in the screen. Anything larger ha a nasty habit of blocking the screen and reducing the flow of oil to the pump. The second and third faults concern the pressure relief valve jamming. Dirt inside the pump can easily jam the pressure relief valve. Jammed inthe open position will cause a loss of pressure and in the closed position will cause excessive pressure.
When installing an oil pump, never use sealants between faces or gaskets. When tightened the sealant will seep out and usually bits of sealant soon break free either inside the pump or sump ready to jam the relief valve. A bit of grease on the gaskets is usually all that is needed. Low oil pressure can also be a result of air being drawn into the pump. Apart from low oil level this may also be caised by too much oil-(the oil will aerate if in constant contact with the moving parts such as the crank), a leaking pick-up pipe, or even a pick-up pipe that is not posistioned at the correct level in the sump. Race engines can also suffer from low-sump oil if the oil does not drain back into the sump at the sam rate at which it is pumped back into the engine. A number of mistakes can also be made during an engine rebuild which result in low oil pressure. Not only should the crank be checked for size against the bearings fitted but also the size of the main bearing housing in the block. Some engines can use bearings that are oversized on their outside diameter.If new camshaft or jackshaft bearings have been fitted ar ethe oil feed holes in the bearings lined up with the holes on the block. Also if any gallery bungs have been moved have they been replaced. On some engines if certain oil bungs are missing the oil can escape behind an engine cover and return the oil back to the pump without any signsof leakage. And finally when installing an oil pump, always read the instructions!!!
CYLINDER HEAD AND GASKETS
To ensure minimum distortion wait for the engine to o cool down before removing the head bolts (4-2 turns a time) in the sequence as per manufacturer instructions. Thoroughly clean the head and block faces and check for true. Clean out all the thread holes in the block- use a drill or blast out with compreesed air. Check the new head gasket-is it correct? Check that the gasket fire ring is not smaller that the cylinder bore -gasket protrusion into the combustion chamber will resultin premature failure.
Some head gaskets are marked TOP or FRONT to ensure correct orinetation when fitted. Most modern composite type gaskets have special coatings and are designed to be fitted dry. A suitable selant may be rquired for some applications-check fitting instructions or with supplier. NOTE-OF CAUTION! Enlarging gasket water way holes willnot improve cooling efficiency. The size, number and position of these holes has been finley calculated by the engine and gasket designers and any alteration may propagate localised overheating and premature engine failure.
Clean and check all cylinder head studs, nuts and bolts-replace if there is any sign of wear, stretch or damage. Most modern engines use stretch bolts and these should ALWAYS be renewed. When refittingthe cylinder head it is recommended that the bolt threads are lightly oiled and installed finger tight ( a light smear of anti-seize compound under bolthead to ease friction during the torquing process is good practice).
Many cylinder heads can be successfully secured using a method of gradual tightening (in incrementsof 20lb/ft) in the sequencd recommended by manuafacturer. However most modern engines employ stretch bolts and these must be tightened in STRICT accordance. Re-torqing conventional cylinder head studs or bolts after an initial engine run is recommended. Always allow aluminium heads to cool completely before carrying out this process.
-----------------------------------------------------------------------------------------------
SPARK PLUGS
How would you like to be shut in a chamber with petrol and given a 30,000 volt electric shock, 25 times a second and be subjected to pressures 50 times greater than normal atmosphere? No?- Well thats what happens to you spark plugs! So, if you want peak performance from your engine make sure you fit suitable plugs.
3 main points to consider are:
1. All modern engines are now fitted with resistor type plugs and you are advised to stick with this type. The high energy bursts from plugs can cause interference to ICE ,EFI and engine management systems if resistor plugs are not fitted.
2. Plug heat range-many plug manufacturers produce a competition range which are usually harder or colder than the standard fitment. For mild tuning it is best to stick with the factorry recommended item but colder plugs will be necessary for seriously modidfied engines.
3. Electrode gap- unless there is a known benefit for doing otherwise, the advice is is to set up the gap. Some uprated ignition systems can generate a spark across a wider gap which may improve combustion. However on highboost turbo engines a large plug gap may result in the spark being blown out and for these engines a reduction in the gap is usually specicfied , eg Cosworth.
10-03-2005, 05:52 PM
#2
garibaldi
Thread Starter
Re: General tech
Originally Posted by the sludge
CON ROD TECH TIPS
LONG RODS
The BDA and 1.6 x-flow engines normally use a 125.2mm con rod with a 44.75mm compression height on the pistonwhich works fine for most applications. However when a high revving competition application is required improvements can be made. By using a long rod (132.8mm length) and a short compression piston height ogf 37.2mm, the piston crown will remain in the same position. By changing these lengths you gain 2 advantages. First the piston is smaller but lighter making it easier to accelerate and deaccelerate during a stroke. Secondly there is less angular movement of the con rod duriong a crank revolution approx 1.8 degrees which equates to around 10.5% reduction. Both eof these advantages result in a freer revving engine.
NARROW JOURNALS
Con rods for BDA, lotus twin cam and x-flow are offered in wide or narrow journal types. Wide journal refers to the width of the big end journal on the con rod being made to the same width as the standard con rod, ie 26.85mm. As an alternative narrow journal rods are also available where the nig end journakl has been reduced to the width of 23.7mm. This givesthe advantages of less rotating mass in the engine, less friction on the big end bearings (as this is narrower) andless drag from oil within the crankcase since the narrow rod will pass through the il with less resistance. In order to use such rods a narrow journal crank must aslo be purchased!
-----------------------------------------------------------------------------------------------
OVERSIZED MAIN BEARING HOUSINGS
Ford haveon too many occasions manufactured engines that haveoversized bearing housings in an effort to reduce the amount of scrapped blocks. Such blocks can however create a nightmare when rebuilding if you do not realise that the block requires special bearings. The result of building an engine with the incorrect bearings is little or no oil pressure and an engine that will be lucky to get a cra around the block beforebeing wrecked. The rule of thumb here is to always check to see what bearings are fitted and never assume. Also always pre-assemble using plasticgauge which will highlight any clearance problems. The engines to llok out for and the relevant measurements of the main beraing housing diameter are
STANDARD HOUSING OVERSIZED HOUSING
CVH 62.287MM-62.308MM 62.687-62.709MM
ESSEX 67.701MM-67.721MM 68.082-68.102MM
X-FLOW 57.683MM-57.696MM 58.064-58.077MM
-----------------------------------------------------------------------------------------------
PISTONS
To reduce piston slap, many pistons have a pin which is offset to the left when viewed from the front. Although all piston crowns are marked accordingly these markings can be inadvertantly removed by additional maching processes. Offset oin pistons fitted ncorrectly will result in mechanical noise and reduced inefficiency. Race pistons defer almost exclusively to a central pin design-a necessity for engine speeds over 10000rpm.
HOW TO MEASURE PISTON SIZES
When measuring pistons to ascertain there bore size, it is essential that they rae measured in the correct place. Pistons are smaller and round at the top but larger and oval at the bottom. You can measure a variance over 0.5mm depending on where it is measured. The correct position is across the skirt of the piston at 90 degress to the gudgeon pin. Also remember that the bores size will be fractionally larger due to the piston clearnce. This can be anything from around 0.02-0.1mm depending on the type of piston.
-----------------------------------------------------------------------------------------------
TIMING BELT PROFILES AND FITTING
The first generation of belt used a straight sided trapeziodial tooth form. Themuch stronger semi-circular formally initially in 8mm pitch is now widely used in a 9.5mm pitch version. Manufacturers develop shapes to improve strength and quietness. Many but NOT ALL are compatible with OE gears so cars is required.
To avoid premature failure the following list should be carried out-
1 ENSURE PULLEYS CLEAN, UNDAMAGED AND UNWORN
2 DO NOT USE A BELT THAT HAS BEEN CRIMPED DURING PACKAGING
3 CHECK THAT TOOTH PROFILE ON BELT MATCHES PULLLEY
4 CHECK TENSIONING JOCKEY WHEEL AND REPLACE IF WORN OR DAMAGED
5. TAKE TIME TO TENSION BELT CORRECTLY AND RE CHECK AFTER 500 MILES
6. REPLACE BELT AT MANUFACTURERS RECOMMENDED INTERVALS.
-----------------------------------------------------------------------------------------------
OIL PRESSURE PROBLEMS
Low or no oil pressure problems form the basis of numerous techincal questions every year. There are numerous likely causes. Before these are described you should be aware that an oil pump does not produce pressure, it produces flow. So, provided the oil pump internals have not worn out excesively then it will be able to produce the flow of oil which it was designed. It is the resistance of the oil galleries in the engine and the size of the clearance between the bearings and crankshaft journals that crate pressure in the oil. Therefore replacing an engines oil pump when the cause of low oil pressure is for example due to excessive clearance between worn crank bearings and journals, will not cure the problem.Always find the cause of the problem before attemting to fix it.
Before attemting to cure a lack of oil pressure are you sure you have a problem? A faulty oil pressure switch may illuminate the warning light so always check with an oil pressure gauge.
OK, assuming that the oil pressure has been measured and is low, does the engine have enough oil in it? Daft thing to ask but is is the first thing to check. A classic problem can occur when a new engine is made up of parts from various sources resulting in the wrong length of dipstick being used. If the oil level is correct is it the correct grade? 0w40 oil for example in a CVH engine wont do it any favours at all. Alternatively if the oi is getting too thin at high temps, then you need to investigate using either a higher viscosity oil and or an oil cooler if one is not already fitted. Has the oil filter been changed on a regular basis? Since its job is to filter impurities from the oil, it gradually fills with debris that will restrict oil flow. If left well beyond its service life it will significantly redice the engines oil pressure.
There are 3 general faults that you tend to get with an oil pump. Firstly if the pumps internals have worn so that the clearances are greater than the maximum alllowed, this will reduce the flow and pressure of oil. Any dirt that is sucked into the pump will accelerate the wear rate of the pump, particulary if the size of theimpurities are greater than the clearances within the pump. Large particles will sginificantly score or in the worst cases jam the pump. Such dirt is allowed to enter the oil pump since it is not filtered, the oil is only filtered after leaving the pump. The metal screen mesh that covers the oil-pivk up pipe only prevents very large particles from entering the pump. Any dirt within the sump is therefore free to enter the pump provided it is smaller than the holes in the screen. Anything larger ha a nasty habit of blocking the screen and reducing the flow of oil to the pump. The second and third faults concern the pressure relief valve jamming. Dirt inside the pump can easily jam the pressure relief valve. Jammed inthe open position will cause a loss of pressure and in the closed position will cause excessive pressure.
When installing an oil pump, never use sealants between faces or gaskets. When tightened the sealant will seep out and usually bits of sealant soon break free either inside the pump or sump ready to jam the relief valve. A bit of grease on the gaskets is usually all that is needed. Low oil pressure can also be a result of air being drawn into the pump. Apart from low oil level this may also be caised by too much oil-(the oil will aerate if in constant contact with the moving parts such as the crank), a leaking pick-up pipe, or even a pick-up pipe that is not posistioned at the correct level in the sump. Race engines can also suffer from low-sump oil if the oil does not drain back into the sump at the sam rate at which it is pumped back into the engine. A number of mistakes can also be made during an engine rebuild which result in low oil pressure. Not only should the crank be checked for size against the bearings fitted but also the size of the main bearing housing in the block. Some engines can use bearings that are oversized on their outside diameter.If new camshaft or jackshaft bearings have been fitted ar ethe oil feed holes in the bearings lined up with the holes on the block. Also if any gallery bungs have been moved have they been replaced. On some engines if certain oil bungs are missing the oil can escape behind an engine cover and return the oil back to the pump without any signsof leakage. And finally when installing an oil pump, always read the instructions!!!
CYLINDER HEAD AND GASKETS
To ensure minimum distortion wait for the engine to o cool down before removing the head bolts (4-2 turns a time) in the sequence as per manufacturer instructions. Thoroughly clean the head and block faces and check for true. Clean out all the thread holes in the block- use a drill or blast out with compreesed air. Check the new head gasket-is it correct? Check that the gasket fire ring is not smaller that the cylinder bore -gasket protrusion into the combustion chamber will resultin premature failure.
Some head gaskets are marked TOP or FRONT to ensure correct orinetation when fitted. Most modern composite type gaskets have special coatings and are designed to be fitted dry. A suitable selant may be rquired for some applications-check fitting instructions or with supplier. NOTE-OF CAUTION! Enlarging gasket water way holes willnot improve cooling efficiency. The size, number and position of these holes has been finley calculated by the engine and gasket designers and any alteration may propagate localised overheating and premature engine failure.
Clean and check all cylinder head studs, nuts and bolts-replace if there is any sign of wear, stretch or damage. Most modern engines use stretch bolts and these should ALWAYS be renewed. When refittingthe cylinder head it is recommended that the bolt threads are lightly oiled and installed finger tight ( a light smear of anti-seize compound under bolthead to ease friction during the torquing process is good practice).
Many cylinder heads can be successfully secured using a method of gradual tightening (in incrementsof 20lb/ft) in the sequencd recommended by manuafacturer. However most modern engines employ stretch bolts and these must be tightened in STRICT accordance. Re-torqing conventional cylinder head studs or bolts after an initial engine run is recommended. Always allow aluminium heads to cool completely before carrying out this process.
-----------------------------------------------------------------------------------------------
SPARK PLUGS
How would you like to be shut in a chamber with petrol and given a 30,000 volt electric shock, 25 times a second and be subjected to pressures 50 times greater than normal atmosphere? No?- Well thats what happens to you spark plugs! So, if you want peak performance from your engine make sure you fit suitable plugs.
3 main points to consider are:
1. All modern engines are now fitted with resistor type plugs and you are advised to stick with this type. The high energy bursts from plugs can cause interference to ICE ,EFI and engine management systems if resistor plugs are not fitted.
2. Plug heat range-many plug manufacturers produce a competition range which are usually harder or colder than the standard fitment. For mild tuning it is best to stick with the factorry recommended item but colder plugs will be necessary for seriously modidfied engines.
3. Electrode gap- unless there is a known benefit for doing otherwise, the advice is is to set up the gap. Some uprated ignition systems can generate a spark across a wider gap which may improve combustion. However on highboost turbo engines a large plug gap may result in the spark being blown out and for these engines a reduction in the gap is usually specicfied , eg Cosworth.
LONG RODS
The BDA and 1.6 x-flow engines normally use a 125.2mm con rod with a 44.75mm compression height on the pistonwhich works fine for most applications. However when a high revving competition application is required improvements can be made. By using a long rod (132.8mm length) and a short compression piston height ogf 37.2mm, the piston crown will remain in the same position. By changing these lengths you gain 2 advantages. First the piston is smaller but lighter making it easier to accelerate and deaccelerate during a stroke. Secondly there is less angular movement of the con rod duriong a crank revolution approx 1.8 degrees which equates to around 10.5% reduction. Both eof these advantages result in a freer revving engine.
NARROW JOURNALS
Con rods for BDA, lotus twin cam and x-flow are offered in wide or narrow journal types. Wide journal refers to the width of the big end journal on the con rod being made to the same width as the standard con rod, ie 26.85mm. As an alternative narrow journal rods are also available where the nig end journakl has been reduced to the width of 23.7mm. This givesthe advantages of less rotating mass in the engine, less friction on the big end bearings (as this is narrower) andless drag from oil within the crankcase since the narrow rod will pass through the il with less resistance. In order to use such rods a narrow journal crank must aslo be purchased!
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OVERSIZED MAIN BEARING HOUSINGS
Ford haveon too many occasions manufactured engines that haveoversized bearing housings in an effort to reduce the amount of scrapped blocks. Such blocks can however create a nightmare when rebuilding if you do not realise that the block requires special bearings. The result of building an engine with the incorrect bearings is little or no oil pressure and an engine that will be lucky to get a cra around the block beforebeing wrecked. The rule of thumb here is to always check to see what bearings are fitted and never assume. Also always pre-assemble using plasticgauge which will highlight any clearance problems. The engines to llok out for and the relevant measurements of the main beraing housing diameter are
STANDARD HOUSING OVERSIZED HOUSING
CVH 62.287MM-62.308MM 62.687-62.709MM
ESSEX 67.701MM-67.721MM 68.082-68.102MM
X-FLOW 57.683MM-57.696MM 58.064-58.077MM
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PISTONS
To reduce piston slap, many pistons have a pin which is offset to the left when viewed from the front. Although all piston crowns are marked accordingly these markings can be inadvertantly removed by additional maching processes. Offset oin pistons fitted ncorrectly will result in mechanical noise and reduced inefficiency. Race pistons defer almost exclusively to a central pin design-a necessity for engine speeds over 10000rpm.
HOW TO MEASURE PISTON SIZES
When measuring pistons to ascertain there bore size, it is essential that they rae measured in the correct place. Pistons are smaller and round at the top but larger and oval at the bottom. You can measure a variance over 0.5mm depending on where it is measured. The correct position is across the skirt of the piston at 90 degress to the gudgeon pin. Also remember that the bores size will be fractionally larger due to the piston clearnce. This can be anything from around 0.02-0.1mm depending on the type of piston.
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TIMING BELT PROFILES AND FITTING
The first generation of belt used a straight sided trapeziodial tooth form. Themuch stronger semi-circular formally initially in 8mm pitch is now widely used in a 9.5mm pitch version. Manufacturers develop shapes to improve strength and quietness. Many but NOT ALL are compatible with OE gears so cars is required.
To avoid premature failure the following list should be carried out-
1 ENSURE PULLEYS CLEAN, UNDAMAGED AND UNWORN
2 DO NOT USE A BELT THAT HAS BEEN CRIMPED DURING PACKAGING
3 CHECK THAT TOOTH PROFILE ON BELT MATCHES PULLLEY
4 CHECK TENSIONING JOCKEY WHEEL AND REPLACE IF WORN OR DAMAGED
5. TAKE TIME TO TENSION BELT CORRECTLY AND RE CHECK AFTER 500 MILES
6. REPLACE BELT AT MANUFACTURERS RECOMMENDED INTERVALS.
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OIL PRESSURE PROBLEMS
Low or no oil pressure problems form the basis of numerous techincal questions every year. There are numerous likely causes. Before these are described you should be aware that an oil pump does not produce pressure, it produces flow. So, provided the oil pump internals have not worn out excesively then it will be able to produce the flow of oil which it was designed. It is the resistance of the oil galleries in the engine and the size of the clearance between the bearings and crankshaft journals that crate pressure in the oil. Therefore replacing an engines oil pump when the cause of low oil pressure is for example due to excessive clearance between worn crank bearings and journals, will not cure the problem.Always find the cause of the problem before attemting to fix it.
Before attemting to cure a lack of oil pressure are you sure you have a problem? A faulty oil pressure switch may illuminate the warning light so always check with an oil pressure gauge.
OK, assuming that the oil pressure has been measured and is low, does the engine have enough oil in it? Daft thing to ask but is is the first thing to check. A classic problem can occur when a new engine is made up of parts from various sources resulting in the wrong length of dipstick being used. If the oil level is correct is it the correct grade? 0w40 oil for example in a CVH engine wont do it any favours at all. Alternatively if the oi is getting too thin at high temps, then you need to investigate using either a higher viscosity oil and or an oil cooler if one is not already fitted. Has the oil filter been changed on a regular basis? Since its job is to filter impurities from the oil, it gradually fills with debris that will restrict oil flow. If left well beyond its service life it will significantly redice the engines oil pressure.
There are 3 general faults that you tend to get with an oil pump. Firstly if the pumps internals have worn so that the clearances are greater than the maximum alllowed, this will reduce the flow and pressure of oil. Any dirt that is sucked into the pump will accelerate the wear rate of the pump, particulary if the size of theimpurities are greater than the clearances within the pump. Large particles will sginificantly score or in the worst cases jam the pump. Such dirt is allowed to enter the oil pump since it is not filtered, the oil is only filtered after leaving the pump. The metal screen mesh that covers the oil-pivk up pipe only prevents very large particles from entering the pump. Any dirt within the sump is therefore free to enter the pump provided it is smaller than the holes in the screen. Anything larger ha a nasty habit of blocking the screen and reducing the flow of oil to the pump. The second and third faults concern the pressure relief valve jamming. Dirt inside the pump can easily jam the pressure relief valve. Jammed inthe open position will cause a loss of pressure and in the closed position will cause excessive pressure.
When installing an oil pump, never use sealants between faces or gaskets. When tightened the sealant will seep out and usually bits of sealant soon break free either inside the pump or sump ready to jam the relief valve. A bit of grease on the gaskets is usually all that is needed. Low oil pressure can also be a result of air being drawn into the pump. Apart from low oil level this may also be caised by too much oil-(the oil will aerate if in constant contact with the moving parts such as the crank), a leaking pick-up pipe, or even a pick-up pipe that is not posistioned at the correct level in the sump. Race engines can also suffer from low-sump oil if the oil does not drain back into the sump at the sam rate at which it is pumped back into the engine. A number of mistakes can also be made during an engine rebuild which result in low oil pressure. Not only should the crank be checked for size against the bearings fitted but also the size of the main bearing housing in the block. Some engines can use bearings that are oversized on their outside diameter.If new camshaft or jackshaft bearings have been fitted ar ethe oil feed holes in the bearings lined up with the holes on the block. Also if any gallery bungs have been moved have they been replaced. On some engines if certain oil bungs are missing the oil can escape behind an engine cover and return the oil back to the pump without any signsof leakage. And finally when installing an oil pump, always read the instructions!!!
CYLINDER HEAD AND GASKETS
To ensure minimum distortion wait for the engine to o cool down before removing the head bolts (4-2 turns a time) in the sequence as per manufacturer instructions. Thoroughly clean the head and block faces and check for true. Clean out all the thread holes in the block- use a drill or blast out with compreesed air. Check the new head gasket-is it correct? Check that the gasket fire ring is not smaller that the cylinder bore -gasket protrusion into the combustion chamber will resultin premature failure.
Some head gaskets are marked TOP or FRONT to ensure correct orinetation when fitted. Most modern composite type gaskets have special coatings and are designed to be fitted dry. A suitable selant may be rquired for some applications-check fitting instructions or with supplier. NOTE-OF CAUTION! Enlarging gasket water way holes willnot improve cooling efficiency. The size, number and position of these holes has been finley calculated by the engine and gasket designers and any alteration may propagate localised overheating and premature engine failure.
Clean and check all cylinder head studs, nuts and bolts-replace if there is any sign of wear, stretch or damage. Most modern engines use stretch bolts and these should ALWAYS be renewed. When refittingthe cylinder head it is recommended that the bolt threads are lightly oiled and installed finger tight ( a light smear of anti-seize compound under bolthead to ease friction during the torquing process is good practice).
Many cylinder heads can be successfully secured using a method of gradual tightening (in incrementsof 20lb/ft) in the sequencd recommended by manuafacturer. However most modern engines employ stretch bolts and these must be tightened in STRICT accordance. Re-torqing conventional cylinder head studs or bolts after an initial engine run is recommended. Always allow aluminium heads to cool completely before carrying out this process.
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SPARK PLUGS
How would you like to be shut in a chamber with petrol and given a 30,000 volt electric shock, 25 times a second and be subjected to pressures 50 times greater than normal atmosphere? No?- Well thats what happens to you spark plugs! So, if you want peak performance from your engine make sure you fit suitable plugs.
3 main points to consider are:
1. All modern engines are now fitted with resistor type plugs and you are advised to stick with this type. The high energy bursts from plugs can cause interference to ICE ,EFI and engine management systems if resistor plugs are not fitted.
2. Plug heat range-many plug manufacturers produce a competition range which are usually harder or colder than the standard fitment. For mild tuning it is best to stick with the factorry recommended item but colder plugs will be necessary for seriously modidfied engines.
3. Electrode gap- unless there is a known benefit for doing otherwise, the advice is is to set up the gap. Some uprated ignition systems can generate a spark across a wider gap which may improve combustion. However on highboost turbo engines a large plug gap may result in the spark being blown out and for these engines a reduction in the gap is usually specicfied , eg Cosworth.
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29-09-2015 03:29 PM
