Complete cheesehead screw set for SOHC engine, in stainless steel with red fibre washers - comprising : 18 screws in total - 4 cambox front bevel screws, 6 rear cambox screws, 7 timing case screws, 1 crankcase screw and high quality fibre washer set (including obligatory spare washer!).

These cheesehead screws are 'bar-turned' in Stainless Steel, to the same dimensions as the original 1930's/50's Norton items - i.e they are machined from solid bar, rather than being mass produced 'pressed thread' items. The primary reason for doing this is that the 'cheesehead' of Norton screws of this item has a distinctive shape and was slightly wider than the proprietary cheeseheads screws available today (many modern cheeseheads are approx 0.370-0.375" head diameter), while ours are larger as per the original Norton profile).

The set consists of 18 CNC manufactured stainless steel screws and 19 high quality red fibre washers (we always include an extra fibre washer - in case you lose one under the bench!).

An original NOS (New Old Stock) Norton cheesehead screw was used as a pattern (see final photograph), these screws copy that profile exactly.

Sorry, not as cheap as some of the mass produced type available - as these screws machined specially for us from oversize bar in small batch's.

Update Jan 2021:  Now back in stock.  We will also shortly be producing similar sets for Norton OHV/SV models and 'Laydown' type Norton gearbox's, email for details at sales@racingvincent.co.uk

This is the 13289(Norton part number) 1/2" x 20 Engine Bolt set - but as fitted to SOHC Norton International Model 30 and Model 40 models, with the rounded head profile as would be expected on roadgoing International models.  It should be noted that Norton themselves actually used a 0.5" Stud with nuts both ends for this bolt on roadgoing models (part No. 12747, which I have elected not to make - but may consider if enough interest - email at normal sales email if you want one) - but that was probably for convenience on the part of Norton's, as a bolt is much more difficult and expensive to machine in this larger size than a stud with two nuts. 

However they did make it as a bolt when fitted to M30/M40 models, but with a wasted head - we also sell that bolt - Item 0727, this item is effectively the same bolt, but with a normal roadgoing rounded head profile for International roadgoing models

Although strictly speaking not original - because on original Norton International and CS1 models the front frame bolt was actually a 0.5" Stud, with nuts both ends, - this set is actually much more in keeping with other engine bolts, in that it is a bolt with the correct 'rounded head, reduced hex' profile of the other engine bolts - only in the next size up (0.705" across flats or 3/8" Whith spanner size), as per the original nut size.

The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. It is as used on all rigid and plunger framed SOHC models from 1930's/50's.  Note, this bolt comes with normal size stainless washers as per these photos - we do also sell special reduced outer diameter 0.5" washers (Item 0662), but these are not always available

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4256 7/16" x 20 front engine bolt set as fitted to Norton International Model 30/40 (pre-Featherbed models), with the correct distinctive 'Norton type' reduced hex and curved head profile.  The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. It is as used on all rigid and plunger framed SOHC models from 1930's/50's 

The E4256 bolt is shown in the 1948 Norton Spare Parts Catalog as 4 being required per engine.  This was probably the case, but actually the front engine bolts have a (front) engine plate on both sides, while one was fitted at the rear above the magneto platfom which only had the engine plate on one side, and the one below the magneto also had an engine plate both sides.  Therefore, we have manufactured 3 variations of this bolt - this being E4256(1): the front engine bolts, two being required per engine.

As there were so many variations of Norton SOHC engine bolts, the table below will help assist you confirm if you are ordering the correct bolt, and you may find this bolt will also fit your bike model for another application :

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4251(Norton part number) 3/8" x 26 Engine Bolt set - front lower crankcase - approx 4pm position as fitted to SOHC Norton International Model 30 and Model 40 models. This has the rounded head profile as would be expected on roadgoing International models.  The set is CNC machined from stainless steel with the correct 'reduced Hex' head and profile, 2 stainless washers and reduced Hex wider nut

The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. It is used on most International 350cc and 500cc International models of the 1930's to 1950's - but check that your engine crankcase is bored to take a 3/8" diameter bolt in this '4pm' position (I have had a couple of crankcases that take 7/16" in this position - but think they may have been re-bored out by later owners) .  

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4262 5/16" x 26 engine cradle bolt set as fitted to Norton International Model 30/40 and all other Norton models if fitted into a 'Cradle' type frame. This bolt has the normal Norton curved head shape and deeper hex than commercial 5/16" bolts.  Two of these bolts are fitted and feed through the bottom frame cradle and engine.  The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. It is as used on all rigid and plunger cradle framed SOHC models from 1930's/50's.

As well as the deeper head on the bolt, the nut fitted to the bolt also has a greater depth than commercially available nuts.  This is important, as this bolt is often overtightened and a normal nut can more easily strip its thread.

Two of these bolt sets are required per engine/bike.

Note - if you have an 'open' framed Norton model - i.e. Norton 16H, 500T, pre-war Model 50 etc, then this bolt will be too long, as this bolt is designed to fit through the cradle as well as the engine.  Sorry, but we do not make the shorter bolt yet, but email us on our sales@racingvincent.co.uk if you require this type of bolt - enough interest and I may make a batch. 

The E4256 bolt is shown in the 1948 Norton Spare Parts Catalog as 4 being required per engine.  This was probably the case, but actually the front engine bolts have a (front) engine plate on both sides, while one was fitted at the rear above the magneto platfom which only had the engine plate on one side, and the one below the magneto also had an engine plate both sides.  Therefore, we have manufactured 3 variations of this bolt - this being E4256(1): the front engine bolts, two being required per engine.

As there were so many variations of Norton SOHC engine bolts, the table below will help assist you confirm if you are ordering the correct bolt, and you may find this bolt will also fit your bike model for another application :

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 5/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4256 7/16" x 20 top/rear engine bolt set as fitted to Norton International Model 30/40 (pre-Featherbed models) - above the magneto, with the correct distinctive 'Norton type' reduced hex and curved head profile.  The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. It is as used on all rigid and plunger framed SOHC models from 1930's/50's 

The E4256 bolt is shown in the 1948 Norton Spare Parts Catalog as 4 being required per engine.  This was probably the case, but actually the front engine bolts have a (front) engine plate on both sides, while one was fitted at the rear above the magneto platfom which only had the engine plate on one side, and the one below the magneto also had an engine plate both sides.  Therefore, we have manufactured 3 variations of this bolt - this being E4256(2): the rear engine bolt just above the magneto platform, one being required per engine.

As there were so many variations of Norton SOHC engine bolts, the table below will help assist you confirm if you are ordering the correct bolt, and you may find this bolt will also fit your bike model for another application :

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4256 7/16" x 20 under magneto/rear engine bolt set as fitted to Norton International Model 30/40 (pre-Featherbed models) - above the magneto, with the correct distinctive 'Norton type' reduced hex and curved head profile.  The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. It is as used on all rigid and plunger framed SOHC models from 1930's/50's 

The E4256 bolt is shown in the 1948 Norton Spare Parts Catalog as 4 being required per engine.  This was probably the case, but actually the front engine bolts have a (front) engine plate on both sides, while one was fitted at the rear above the magneto platfom which only had the engine plate on one side, and the one below the magneto also had an engine plate both sides.  Therefore, we have manufactured 3 variations of this bolt - this being E4256(3): the rear engine bolt just below the magneto platform, one being required per engine.

As there were so many variations of Norton SOHC engine bolts, the table below will help assist you confirm if you are ordering the correct bolt, and you may find this bolt will also fit your bike model for another application :

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4251 3/8" x 26tpi below magneto/rear engine bolt set as fitted to early Norton International Model 40/Pre 48 Manx Model 40M (pre-Featherbed models) - as fitted below the magneto, with the roadgoing type distinctive 'Norton type' rounded head/reduced hex curved head profile.  The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. 

The engine bolts fitted to 350 SOHC engines are a bit more confusing than the 500 versions, because there were commonly 2 sizes of crankcase - the earlier type as shown in these photographs being physically smaller than the 500cc versions.  However, in 1948 the 350 and 500 crankcases were standardised on the larger 500cc crankcase casting.  

I do not profess to be an expert on all the 350 variants, but know that on many of the smaller/earlier type 350cc crankcase casting, the rear 10pm and 11pm (above and below magneto platform) were of 3/8" shaft diameter - rather than the 7/16" shaft version fitted to 500cc and later 350cc crankcases (0718/0719 and 0724/0725).

So please check your crankcase to be sure, but if you a (350) crankcase with 3/8" shaft bolt diameter in the 10pm position (i.e. just below the magneto platform), and wish to fit the roadgoing 'rounded' head, then this is the bolt you need.

Note 1: In the 1948 Norton Spare Parts catalog the E4251 bolt is shown as fitted to the earlier 40M (early 350 Manx) crankcase.  We do also make this bolt with Manx style 'wasted head', that is item listing - 0722, but this version (which we have classed E4251_Int) has the 'rounded head' profile which was more commonly fitted to roadgoing models and pre-war crankcases.

Note 2: Norton look to have fitted the same engine bolt both above and below the magneto platform (i.e. 11pm and 10pm).  Because there was only an engine plate on one side above the magneto, I offer this bolt in 2 lengths, this being the slightly longer version fitted below the magneto platform.

As there were so many variations of Norton SOHC engine bolts, the table below will help assist you confirm if you are ordering the correct bolt, and you may find this bolt will also fit your bike model for another application :

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the E4251 3/8" x 26tpi above magneto/rear engine bolt set as fitted to early Norton International Model 40/Pre 48 Manx Model 40M (pre-Featherbed models) - as fitted above the magneto, with the roadgoing type distinctive 'Norton type' rounded head/reduced hex curved head profile.  The set consists of hex head bolt, deep nut and two washers - CNC manufactured by ourselves in Stainless Steel. 

The engine bolts fitted to 350 SOHC engines are a bit more confusing than the 500 versions, because there were commonly 2 sizes of crankcase - the earlier type as shown in these photographs being physically smaller than the 500cc versions.  However, in 1948 the 350 and 500 crankcases were standardised on the larger 500cc crankcase casting.  

I do not profess to be an expert on all the 350 variants, but know that on many of the smaller/earlier type 350cc crankcase casting, the rear 10pm and 11pm (above and below magneto platform) were of 3/8" shaft diameter - rather than the 7/16" shaft version fitted to 500cc and later 350cc crankcases (0718/0719 and 0724/0725).

So please check your crankcase to be sure, but if you a (350) crankcase with 3/8" shaft bolt diameter in the 11pm position (i.e. just above the magneto platform), and wish to fit the roadgoing 'rounded' head, then this is the bolt you need.

Note 1: In the 1948 Norton Spare Parts catalog the E4251 bolt is shown as fitted to the earlier 40M (early 350 Manx) crankcase.  We do also make this bolt with Manx style 'wasted head', that is item listing - 0722, but this version (which we have classed E4251_Int) has the 'rounded head' profile which was more commonly fitted to roadgoing models and pre-war crankcases.

Note 2: Norton look to have fitted the same engine bolt both above and below the magneto platform (i.e. 11pm and 10pm).  Because there was only an engine plate on one side above the magneto, I offer this bolt in 2 lengths, this being the slightly shorter version fitted above the magneto platform.

As there were so many variations of Norton SOHC engine bolts, the table below will help assist you confirm if you are ordering the correct bolt, and you may find this bolt will also fit your bike model for another application :

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

Therefore - when comparing the length shown in the table above to your own engine, you need to take into account the width of the engine casting, engine plates and the height of the nut.  Also, any brackets that you may fit under the bolt head - I have tried to base the length of bolts on not having additional brackets unless I know they were standard (the nuts are normally extra width though and can be narrowed slightly if necessary, or one of the washers omitted

Remember that in some cases, bolts were fitted where there may have only been an engine plate on one side - i.e for the rear of the engine on most SOHC engines, the bolt immediately above the magneto platform has an engine plate only on one side, while the bolt under the magneto has an engine plate on both sides - which is why I make 2 versions of these bolts.  Norton did not bother originally, fitting the same length bolt to both)

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

In most cases, orginal 'New Old Stock' Norton bolts were used as templates for these bolts - although being practical - it is very hard to tell what is absolutely original or nut for each engine! - there were so many bolt variations and lengths over the years, with some engines seemingly using different lengths and shaft diameters for the equivelant engine by the year.  It is worth noting particularly that pre 1948/49 350cc cranckcases are physically smaller than the equivelent 500cc crankcase - but they standardised them in 1949

Therefore - please check your own engine to check which ones you require before purchasing, and double check the fit before final tightening - in case you need to return.  We hope you understand, we will not accept returns if you have marked the finish of the hex or shafts as we will not be able to resell.  Email us on our normal sales@racingvincent.co.uk if you need any more information before ordering.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!

This is the distinctive E4268 7/16" x 20 tpi BSC short engine bolt that was used to bolt the rear engine plates to the upright frame tube on most 1930s - 1950s Norton frames.  These are CNC machined by us in stainless steel (with linished flats). 

Frames using upright gearbox's used two nuts per frame, later flat gearbox frames used 4 nuts per frame.  They were also used to close off the bottom of the rear plunger shaft on Gardengate frames (fitted with a thick washer, to lock them to the frame)

As can be seen from the third photograph, where our bolt is alongside an original 'New Old Stock' Norton E4268 bolt, ours are identical in thread, hex size and head shape to the original  - other than ours are just machined in non rusting stainless steel and look a bit nicer!

Bolt Table Legend and Useful Information: 

AF = "Across Flats', i.e the diamter in inches of hex bar between the two opposite flats - this is the diameter the spanner gap needs to be - we use the correct 'British Standard' bar, as fitted to all Norton single cylinder motorcycles originally, to fit BSW spanners. 

UH = 'Under Head' Bolt Length, i.e. when measuring the length of the bolt shaft - dimensions are taken from the distance at the base of the hex head to the end of the threaded shaft.  It does not take into account the height of the hex head, or the slightly rounded chamfer at the end of the threaded shaft, which are additional.  (Please bear in mind length is nominal - there may  be 1 or 2 mm variation because of batch variation). 

'Rounded Head'/Reduced Hex Head : Norton's used a distinctive rounded dome on many of their larger engine bolts - these are replicated exactly on our bolts, as the photographs show.  This style of head was used on many Norton bolts of the '30's-'50's. 

In addition many engine bolts had an AF (Across Flats) diameter that was less than normal commerically available bolts for a given bolt shaft size - the rationale for this was that there was not much room around complex castings, therefore you needed to be able to get access with a smaller spanner.  To allow for this, many of the engine bolts with these 'reduced head size to shaft diameter' bolts also had a deeper depth of hex as well, to provide as much spanner to hex contact as normal bolts - reducing the chance of 'rounding' the hex when applying a lot of pressure with spanners and providing as much thread on the nuts as possible - but important with the pressure required of engine bolts.  We have replicated these deeper heads, with reduced hex diameter to shaft as per the originals, not only giving that authentic look, but ensuring the nuts .  To our knowledge this type of bolt/nut is not  had, as well as a smaller hex (reduced head) than is normal for a commercially available 7/16" bolt.  They are very distinctive and I always struggle to find these when restoring or building a project Norton.

Bolt Radial Position In Relation To Crankcase:  In the table above I show the radial position of the engine bolt listed here, in relation to the crankcase, if looking on the Timing side of the crankcase as a Clock Dial.  Therefore, the front engine bolt closest to the front down tube and on the horizontal datum line with the mainshafts would be - 3pm, hope this makes sense!  I expect most owners used to Norton single engines try and work out in their head the relative positions of engine bolts in the same way. Clock times are approximate!

Thread Type:  Engine Bolts on Norton engines tended to come in most of the standard British Whitworth diameters, with the following common thread types, where TPI means 'threads per inch':  1/4" (shaft diameter) x 26 tpi (Threads per inch), 5/16" x 26 tpi, 3/8" x 26 tpi, 7/16" x 20 tpi, 1/2" x 20 tpi.

Most thread profiles were originally BSC (British Standard Cycle), but please note that 7/16" x 20tpi is also a UNF standard thread size and none of the tooling manufacturers will now make the BSC profile tooling - therefore we manufacture this size nut/bolt in UNF profile.  These nuts may fit on original bolts, but can be slightly tighter.

Overall, these bolts are high quality, CNC machine finished engine bolt sets manufactured to look just as the original Norton items, but in non rusting stainless steel, with original Norton dimensions and profiles.   We linish the hex faces on the bolt heads to ensure crisp finishes and we hope you find the will give that finishing touch to any restoration - or just clean up the look of your oily rag, ride to work Norton!