The following listings show a variety of inlet and exhaust valves as commonly fitted to SOHC Norton engines.  However, before selecting the valves that best suit your needs - here is some general information about the valves we provide, and some useful information about SOHC Norton valves

(please remember - this information is based on our own experiences of stripping original engines - and should only be taken as useful information - not specific guidance for your own needs - it is always the customers responsibility to ensure they are comfortable with their choice and fitment of valves - and all responsibility of fitment lies with them). 

• Our valves - G&S:  Almost all the valves you see listed here are manufactured for us by G&S Valves - one of finest and longest established UK manufacturers of high quality valves.  All valves are manufactured to well established dimensions from a G&S drawing, to established SOHC dimensions and radiuses. 
• Because there were so many size variations offered over the years of manufacture - realistically we can only get each variation manufactured in small quantities - because of this the Unit Price of the valves shown here are far more expensive than some other valves for other marques or models you might find offered elsewhere - even other G&S valves - where they may have been manufactured for a more common engine model, in larger quantities.  Hopefully it goes without saying - it is better for a valve to be available, even if not cheap - rather than it not beint available at all.
• As of the end of 2023 - G&S valves (like so many UK manufacturing companies) had to announce heavy price increases following Covid and recession manufacturing cost incresases, particularly heat treatment costs.  Sorry - as of early 2024 we have had to raise our own prices considerably (but fyi - we have not passed on the full price/margin increase).
• Many of the following listings are 'multiple' listings - i.e. there is more than one variation for each listing.  To check availability - go to the lisitng, select the required valve in the 'dropdown' box - and if the valve is in stock it will show with a GREEN bar.  If out of stock - you can email us at paul.norman@racingvincent.co.uk to see if we have plans to get a new batch made (or if already in progress)
• Occasionally we may offer 'New Old Stock' valves if from a reputable source.  If so - we will clearly identify those valves - and make it clear if they are not of known G&S manufacture  

General Information for Norton SOHC (and early DOHC Valves):

• Generally - for most (Arthur Carrol designed) SOHC engines - a parrallel collet groove was used (this is different to most OHV and SV Norton models, which generally employed a conical collet groove)
• As a normal rule - SOHC inlet valves were of 11/32" valve stem diameter.  Exhaust valves were of 3/8" diameter (as were most OHV engines for both inlet and exhaust).  I am not sure at what point 5/16" valve stems were employed for the later SOHC (and early DOHC) Manx engines - but it it not unusual to find a later 'square' Manx head fitted with 5/16" stem valves for both inlet and exhaust.  We offer a small selection of 5/16" valves - which most have larger heads, more suitable for competition engines
• Normally - inlet valves had a concave valve head and exhaust valves had a flat valve head
• Some earlier SOHC Engines (i.e. Walter Moore CS1) engines look to have used valves fitted with a conical collet groove.  We are not experts on these earlier engines - but I am told it is not uncommon for early CS1's to be fitted with later ES2 valves and collets - which we can also offer, in our OHV section, or you can email us for more information before ordering
• Head Diameter:  There have been lots of variations in Norton SOHC valve head sizes - often with the inlet valve diameter being larger than the exhaust valve.  We offer many of the generally accepted 'standard' head sizes (i.e. 1.735"/1.750" being a common inlet head size on roadgoing 500cc Inter models) - as well as some of the larger sizes often found on those engines tuned for competition
• If changing your valve size as part of a rebuild or tuning exercise - remember you should always check clearances on rebuild - particularly valve to piston clearance if enlarging valve size.  As a general rule - I always used to look for a minimum 60 thou valve to piston clearance when building a competition engine
• Head diameter and valve seats:  Remember if replacing valves and unable to find the exact replacement valve diameter - that the cylinder head valve seat can be checked - as often the actual valve seat surface on the valve itself is far less than the width of the 'cut' valve seat - so you may find that a 1.750" valve will fit your cylinder head - even if the original valve was 1.735" - if the valve seat allows it.  But see point above about checking clearances etc
• Valve Length:  It seems that SOHC valves were supplied in variety of lengths - we believe this was mainly to allow for correct placement of the cambox - the ideal position of that being - where the rocker arm adjuster centre line (ideally) would be directly over the centre line of the valve, when the cam was at approximate mid lift.  In reality, this is often difficult to achieve - and some sort of slight compromise is required.  However - it was common practice to buy valves with a longer 'Blank Shaft', so the ideal height could be calculated by the engine builder, then cut to length and the collet groove cut.  I know that well known SOHC expert Stu Rogers always used to cut his own valves to length when building an engine (as do I, when not having the required length for an engine I am building).  Because of this - as well as supplying valves to a specific length (with collet already cut, ready to fit) - for most of the common valve types - we also provide a 'Blank Shaft' variant - where the customer can cut the valve to their own length.  If taking this option - for both inlet and exhaust variants we can provide the required collet groove dimensions - as used by G&S.  Sorry - but generally we no longer cut blank shaft valves to custom any more - the setup time for one valve is normally prohibitive to the customer!!  But feel free to email us if you require more information or advice
• Valve Caps:  As far as I know - Norton's did not originally offer valve caps in their SOHC Norton Spare Parts list - but we know that many customers and tuners have requested them and have fitted them over the years - we assume this is because it easily allows for small discrepancies in length between inlet/exhaust valve length, or cambox height discrepancies.  Because of this - we do offer both 11/32" and 3/8" valve caps in a couple of thicknesses - but fyi - it is up to the customer to decide if they wish to fit these - and at their own responsibility.  They are however, patterned on original 'Terry's' valve cap originals - using their dimensions.

- High quality inlet valves manufactured by G & S Valves - Following Head Sizes available (check your original) : 1.750" or 1.790" diameter.  Standard Model 30/40 stem diameter : 11/32".  This listing is for a valve with a blank stem (no groove machined) so you can cut it to length and machine the collet groove yourself, if the valve you are replacing is not one of our standard lengths.

Machining the valve to the same length as your original is the best way to ensure that you will have a valve the correct length for your cambox and spacing between cambox and head, particularly important if you are replacing a valve with a more obscure length. This type requires you undertake the final cutting to length yourself.

The last picture for this listing gives the collet groove dimensions - as are performed by G&S on the 'sized' valves, so you can machine these valves to the correct dimensions.

Note: If you wish us to cut the valve to length and machine the collet groove, please email separately with order - expect £12 charge per valve, and turnaround time of at least 3 weeks.

- High quality inlet valves manufactured by G & S Valves - Following Head Sizes available (check your original) : 1.750" or 1.790" diameter. Standard Model 30\40 stem diameter : 11/32" - Stem length: 4.590".

These valves already have the collet groove machined and are ready to fit. Note: Norton cammy valves were made in a variety of lengths over the years, however, this length - 4.590" is one of the most commonly used. If you have an original then measure that. If you are unsure please email me.

High quality inlet valves manufactured by G & S Valves - These are 3 lengths/head sizes commonly fitted to 500cc roadgoing International models - Following Head Sizes available (check your original) : 1.735", 1.750" or 1.790" diameter." - Stem length: 4.590" or 4.625" (two relatively common lengths).

These valves already have the collet groove machined and are ready to fit. Note: Norton cammy valves were made in a variety of lengths over the years, however, the- 4.590" is one of the most commonly used, and 4.625" (or within a few thou of that - which can be taken up by the rocker adjuster if your opposing exhaust valve is a few thou different) is also one of the more common lengths.

If you have an original you are looking to replace - then measure that first - 11/32" valve stem diameter and a concave valve head normallly denote an inlet valve. 

The length of your valve is measured most eaily by placing the valve onto a flat surface valve head up, then run a digital caliper from the face of the valve head to the flat surface below.  A few thou difference between inlet and exhaust valve length can easily be adjusted for by the adjustment in the 3 piece rocker adjuster - but when measuring valve lengths (particularly when building an engine from parts) - ideally the length is adjusted so the cambox height allows for the rocker pad to be centralised with the centreline of the valve, when the cam is at approximate half lit.  Sometimes a slight compromise is called for

The head diameter should be measured across the overall diameter.  1.735" was an original standard Norton inlet valve size for SOHC 500cc engines - but 1.750" is a very common replacement - particularly if the valve seats have been re-cut - so it is always useful to measure the outer diameter of the inlet valve seat (particularly after re-cutting), as this will tell you the maxinum valve diameter that will fit your engine.  Remember - if fitting larger valves than were previously fitted - always to plasticine the top of your piston on reassembly - to ensure you have sufficient valve to piston clearance.  I always used to look for a minimum of 60 thou valve clearance when building a race engine.

If you are unsure you can email us for guidance and availability before ordering - on paul.norman@racingvincent.co.uk.

- High quality inlet valves manufactured by G & S Valves - This valve is in a larger head size - 1.825". It was sometimes fitted to later International's and SOHC Manx's (but can also be fitted to earlier engines if req'd) - standard Model 30\40 stem diameter : 11/32" - Stem length: 4.650".

These valves already have the collet groove machined and are ready to fit. Note: Norton cammy valves were made in a variety of lengths over the years. Thiis length - 4.650" is also relatively common (and I believe more so with the larger valve size). If you have an original then measure that. If you are unsure please email me.

- High quality inlet valves manufactured by G & S Valves - This valve is in a larger head size - 1.855". Probably the largest diameter head inlet valve fitted to SOHC Norton engines, this head would normally only be fitted to racing engines (I think I have one of these fitted in one of my racing methanol heads. Standard Model 30\40 valve stem diameter : 11/32" .

We offer these valves in 3 different valve stem lengths:

0033E:  4.650" Valve Stem Length- These valves already have the collet groove machined and are ready to fit. Note: Norton cammy valves were made in a variety of lengths over the years. This length - 4.650" (one of the most common lengths)

0033F:  Blank Stem - these valves have an extra long stem (4.875" overall length), but with no collet grooves cut yet.  This is the most flexible length, as it allows you to cut the valves to the correct length for your own engine/cambox combination.  However - you will need to cut them to length yourself and machine the cotter groove - we can supply dimensions for doing this as required

0033G:  4.590" Valve Stem Length- These valves already have the collet groove machined and are ready to fit. Note: Norton cammy valves were made in a variety of lengths over the years. This length - 4.590" (one of the most common lengths)

Obviously - when fitting valves this large (which really would only be used on a high spec competition engine), it is very important to slowly turn the engine over with valve timing set as the engine is run, and plasticine fitted to the piston crown - to ensure there is sufficient valve/piston clearance.  This should be done slowly at first - in case parts do touch, and be ready to stop turning the engine if you feel resistence!

Please email on sales@racingvincent.co.uk if you want more information on cutting cotter grooves on blank stem valves

High quality inlet (or Exhaust) valves manufactured by G & S Valves for later SOHC 30M/Manx heads fitted with 5/16" stem valves. Available in 2 valve head diameters and 2 stem lengths.  

These valves are 5/16" stem diameter and are of the type fitted to some later Norton SOHC Manx heads, or early DOHC (pre-Featherbed) heads. Unlike earlier SOHC heads - which were fitted with 11/32" stem valves on the Inlet side and 3/8" stem valves on the Exhaust side - the later SOHC (and then DOHC heads) would have 5/16" stem valves on both Inlet and Exhaust side.

We can offer these 5/16" Stem diameter valves in 4 variations:

0034a: 1.750" Valve Head Diameter, with the valve length (with cotter groove) of 4.545" overall length (which was copied from an old genuine Norton valve length) 

0034b: 1.750" Valve Head Diameter, with a blank valve stem (overall length 4.875"), so the valve stem can be cut by the customer to the correct length for their cambox (i.e. either SOHC of DOHC type cambox) 

0034c: 1.790" Valve Head Diameter, with the valve length (with cotter groove) of 4.545" overall length (which was copied from an old genuine Norton valve length) 

0034d: 1.790" Valve Head Diameter, with a blank valve stem (overall length 4.875"), so the valve stem can be cut by the customer to the correct length for their cambox (i.e. either SOHC of DOHC type cambox) 

I gather when they were fitted - the same stem diameter were fitted to both Inlet and Exhaust valves (I would expect it was more normal to fit the bigger head size to the inlet valve).

We can also supply 5/16" SOHC/DOHC type collets to fit our valve cups (see Item 0280 and 0040b).  However, we do not currently supply 5/16" valve guides - but email us at sales@racingvincent.co.uk if you require them - we may consider having a batch made in the future (this update being Nov 2021).

If you wish us to cut the valve to length and machine the collet groove, please email seperately with order, dependent on how busy we are, we do sometimes carry this task out on our CNC- expect £12 charge per valve, and turnaround time of at least 3 weeks.

Note: as well as fitted to some late SOHC (Gardengate) Manx heads, this size of valve stem may also have been fitted to early DOHC Manx Longstroke engines.  You will need to check your valve stem length, but you may find the blank stem versions of these valves could be fitted to this model of engine - you will need to check your machine.

High quality SOHC valves manufactured by G & S Valves - This listing being for those valves commonly fitted to roadgoing Featherbed (500cc) Model 30 International models.

These valves are as per pre-Featherbed 500cc Inter valves - i.e. 11/32" stem inlet valves or 3/8" Exhaust valves (with the standard SOHC Inter flat valve head commonly fitted to Norton SOHC models), but have a slightly longer valve stem length of 4.750" - which can be seen at the top of the valve stem, the area above the collet groove being taller than earlier valves.

The Inlet valve has a head diameter of 1.750" while the exhaust valve has a head dimension of 1.735".

I am not an expert on Featherbed Inter models - but I am told by an established expert on them these were the most common dimensions for the 500 Featherbed International - but I recommend you check your own engine existing valves before ordering.

Both valve types being slightly longer than earlier Inter engines - with a valve stem of 4.750" length (sized for collet).  Price is each  

These are 'New Old Stock' (i.e. not our modern G&S manufacture) inlet valves - i.e. with standard Norton International 11/32" stem Inlet valve and with the most common original Norton Model 30 International head diameter - 1.735".

They have the collet groove already machiined and an overall length of 4.600" sized - which is only 10 thou different to one of the most common SOHC  lengths - 4.590 (which we normally offer in our G&S Valve range). 

Price is Each

Background: These were recently acquired from a long standing established Norton SOHC collector and officiando, and have been with him for many years as part of his normal stock.  He was not entirely sure - but believed they may be original Norton SOHC valves - 'New Old Stock'.  The valves look brand new (though of course they dont look quite as shiny as our normal newly manufactured G&S valves) - and have all the normal shape and design of the other Norton International inlet valves we sell.  Most importantly - if you look closely at the top of each valve - you can see that it is etched/stamped with the words: 'E6240 G2 NB' . . . and it was not unusual to find original Norton valves with writing on them similar to this.

There is a small chance they may have been G&S originally (as they are a long established manufacturer) - but they have now writing on them to confirm this, and as we cannot guarantee origin of manufacture . . . we can only say, they are 'New Old Stock' valves.

We only have limited stock of these valves - and once they are gone they are gone!

We hope you will understand - but because these are 'New Old Stock' - and we cannot guarantee who manufactured them  . . . they are sold as seen - and all responsibility is with the customer.  However, like all our products - if after purchase, you wish to return one - we have a full refund policy (providing not fitted or marked, and in same packaging as supplied)

- High quality exhaust valves manufactured by G & S Valves. - Following Head Sizes available (check your original) : 1.735" and 1.750". Standard Model 30/40 stem diameter : 3/8". Stem length: 4.875".

Left blank at end, so these can be cut to the same length as your original, and then the collet groove machined afterwards. This is the best way to ensure that you will have a valve the correct length for your cambox and spacing between cambox and head, particularly important if you are replacing a valve with a more obscure length. This type requires you undertake the final cutting to length yourself.

The last picture for this listing gives the collet groove dimensions - as are performed by G&S on the 'sized' valves, so you can machine these valves to the correct dimensions.

If you wish us to cut the valve to length and machine the collet groove, please email seperately with order - expect £12 charge per valve, and turnaround time of at least 3 weeks.