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!

Single row ball bearing - Fitted to the outer of the two driveside mainshaft bearings in the crankcase on all SOHC engines, both International and early Manx.  Originally Norton would have fitted a slightly looser tolerance 'C3' fit bearing, but with them now being obsolete, the next best thing is still to take the same bearing - from top quality UK manufacturer RHP - but these being the standard (STD) tolerance.

Jan 2023:  Sorry to say, that just like all other SOHC RHP C3 (loose tolerance) bearings, Item 0018 (C3 version) - are now obsolete and we are only able to get them in occasionally as we find them - however, this STD fit bearing (0018B) is still the same high quality RHP bearing of the correct type, we just recommend that when running the engine in, you give it a few more miles to let it bed in fully.

Like all other original 'Imperial' fit high quality RHP bearing - they are now obsolete and are difficult to obtain - however, much better to fit best quality RHP bearings when we are able to obtain them, rather than a lesser offshore manufactured bearing

By the way - it is worth pointing out - as I sometimes get asked this by customers:  a 'C3' fit bearing, just means it is slightly looser tolerance than the STD fit bearing.  This means (as they are normally fitted into crankcases with an interference fit), that once fitted - they will spin more freely than a STD fit bearing initially.  When used on a racing bike, where less time is allowed for 'running in' this can make a difference . . . but on a road bike - using a STD bearing should not be an issue . . . I would normally just allow 500 - 750 miles of steady running in first (and actually - many old owners were probably not aware of what a 'C3' bearing is, I have stripped many engines and found replacement STD bearings already fitted!).

This is a very useful tool, that no workshop should be without - a plastic circular valve/ignition disc, with hole that can be opened out to suit all Norton singles. 

Price is Each

These plastic discs can be attached to the end of the crankshaft, and a piece of welding wire turned into a needle against the circumference - with degrees marked all around the disc - they are invaluable for setting both valve and ignition timing.  Even better if you buy a sheet of alloy plate and glue one of these discs to the plate to make them stronger.  I always keep a couple like this around the workshop.

- Modern equivelant Dowty washer (outer washer is zinc plated steel, inner washer is neoprene). This washer is used behind the timing chamber filter bolt and also at the back of the rear cylinder crankcase mouth bolt (that has an oil feed).

It can also be used behind 1/4 BSP fittings - but I prefer to use copper or red fibre on those applications, as they look more original

These Red Fibre Washers are a smaller diameter than 'normal' 1/4" BSP washers - but then pre-threaded by us - so they are a good fit on those Norton fittings that used 1/4" BSP thread, but have a groove behind the thread - e.g. Norton pre-48 Oil Sump Plugs and some breather union fittings. 

This listing is for a pair of washers (i.e. x2)

Background:

For anyone that is familiar with Norton single cylinder models (and earlier twins) - they will know that it was not unusual to make some oil and petrol fittings with a 1/4"BSP thread, but with a groove machined between the thread and the rear face of hex spanner head.  Added this, often the hex was not very wide (what you will see referred to as 'Reduced Hex' by us throughout this catalog for Norton specific fastenings), so there was little hex face for the fibre washers to seal against.  

The two best examples of this are the Pre-48 style 1/4" BSP Norton Sump Plug (in all its guises) and some breather unions (see photographs - some Unions had grooves, while others did not).

Therefore, if you try and fit a 'normal' 1/4" BSP red fibre washer to this type of sump plug or union - it will go on easily, but when it gets to the groove - it will wobble around.  Then, when the sump plug or union it tightened, the wobbling washer will normally move over to one side - and there will be a very good chance it will leak, or just crush and break up when tightened.

In the past we have sold this size of 'tighter fit' washer - telling customers they will need to be prepared to use some force to wind the washer past the thread - but franky - the best quality red fibre washers are very hard, and extremely difficult to wind onto the thread!

Therefore, as part of work we did in early 2022 to replicate most Norton sump plugs, we also looked at how we could make this easier - and eventually have come up with a jig process to pre-thread these washers with a 1/4" BSP thread - as shown here.

So, although not very thick - if you look closely at these washers you will see they have an intenal thread cut into them (see also the taper tap we use for this process) . . . and that means that, although still tight, they can now be carefully screwed onto a 1/4" BSP thread by hand - but will be a 'Size' fit on the groove behind the thread - therefore giving a much better chance for the washer to seal properly!

If trying to tap a single washer, it will normally just crush the washer, but with experimentation and a jig, we have come up with a process to manualy thread these washers, so they will just 'screw on' by hand.

This may sound like a simple issue . . . but actually most proprietary 1/4" BSP washers are actually quite loose on a 1/4" BSP thread (see our Item 1111 for 1/4" BSP washers that are a good fit!), but good quality red fibre washers are normally much harder than cheap washers - the washers we use are supplied by one of the best (and most expensive!) washer suppliers - and therefore require this pre-threading process . .. trying to screw it on without doing this is almost impossible.

Sorry these washers are so expensive for what looks such a simple and cheap looking thing - but hopefully you will understand that the jig and time it takes to manually thread them is what results in the extra cost - but definitely worth using if you prefer the original type Red Fibre washerer, rather than modern Dowty (nitrile/steel) washers.

We also sell these as a bag of 5 (Item 0249), or close fitting 'normal' 1/4" BSP washers (Item 1111) for those unions and tap fittings which dont have a groove behind the thread 

These Red Fibre Washers are a nice close fit on 1/4" BSP threads and are useful for many Norton fittings - such as those breather unions and petrol taps that have a 1/4" BSP thread that comes up close to the hex or shoulder.

We bring thsese washers in specially for this purpose.

Price is per pair.

Although it may sound obvious - good close fitting 1/4" BSP red fibre washers are actually quite difficult to find these days - most washers advertised as 1/4" BSP are actually a slightly sloppy fit on that thread - resulting in only a limited amount of material actually sealing when the washer is fitted (we know this - because we have looked at those supplied by many manufacturers over the years!

These washers are a good close fit to the thread and work best where there is no groove behind the thread - allowing the washer to be as effective as possible, i.e. the non shouldered breather unions (our Item 0248 - as shown in the listing pictures) often fitted to Norton single models.

These are good for things such as Norton single models - crankcase One Ways Valves and those breather unions which do not have a groove behind the the thread, and of course things such as 1/4" BSP fuel taps.

Note: we also sell special 'Pre-threaded' tight fit 1/4"BSP fibre washers for those Nortin fittings that do have a groove behind the thread - i.e. orgiinal pre-48 Sump Plugs and some unions - see Item 0249 and 0941

These Red Fibre Washers are a smaller diameter than 'normal' 1/4" BSP washers - but then pre-threaded by us - so they are a good fit on those Norton fittings that used 1/4" BSP thread, but have a groove behind the thread - e.g. Norton pre-48 Oil Sump Plugs and some breather union fittings. 

This listing is for a bag of 5 washers

Background:

For anyone that is familiar with Norton single cylinder models (and earlier twins) - they will know that it was not unusual to make some oil and petrol fittings with a 1/4"BSP thread, but with a groove machined between the thread and the rear face of hex spanner head.  Added this, often the hex was not very wide (what you will see referred to as 'Reduced Hex' by us throughout this catalog for Norton specific fastenings), so there was little hex face for the fibre washers to seal against.  

The two best examples of this are the Pre-48 style 1/4" BSP Norton Sump Plug (in all its guises) and some breather unions (see photographs - some Unions had grooves, while others did not).

Therefore, if you try and fit a 'normal' 1/4" BSP red fibre washer to this type of sump plug or union - it will go on easily, but when it gets to the groove - it will wobble around.  Then, when the sump plug or union it tightened, the wobbling washer will normally move over to one side - and there will be a very good chance it will leak, or just crush and break up when tightened.

In the past we have sold this size of 'tighter fit' washer - telling customers they will need to be prepared to use some force to wind the washer past the thread - but franky - the best quality red fibre washers are very hard, and extremely difficult to wind onto the thread!

Therefore, as part of work we did in early 2022 to replicate most Norton sump plugs, we also looked at how we could make this easier - and eventually have come up with a jig process to pre-thread these washers with a 1/4" BSP thread - as shown here.

So, although not very thick - if you look closely at these washers you will see they have an intenal thread cut into them (see also the taper tap we use for this process) . . . and that means that, although still tight, they can now be carefully screwed onto a 1/4" BSP thread by hand - but will a 'Size' fit on the groove behind the thread - therefore giving a much better chance for the washer to seal properly!

If trying to tap a single washer, it will normally just crush the washer, but with experimentation and a jig, we have come up with a process to manualy thread these washers, so they will just 'screw on' by hand.

This may sound like a simple issue . . . but actually most proprietary 1/4" BSP washers are actually quite loose on a 1/4" BSP thread (see our Item 1111 for 1/4" BSP washers that are a good fit!), but good quality red fibre washers are normally much harder than cheap washers - the washers we use are supplied by one of the best (and most expensive!) washer suppliers - and therefore require this pre-threading process . .. trying to screw it on without doing this is almost impossible.

Sorry these washers are so expensive for what looks such a simple and cheap looking thing - but hopefully you will understand that the jig and time it takes to manually thread them is what results in the extra cost - but definitely worth using if you prefer the original type Red Fibre washerer, rather than modern Dowty (nitrile/steel) washers.

We also sell these as a pair (Item 0941), or close fitting 'normal' 1/4" BSP washers (Item 1111) for those unions and tap fittings which dont have a groove behind the thread