This is the rarest of all SOHC outer timing covers - the pre-1938 'Ribbed' type outer timing cover, but made in magnesium. As far as I am aware, there were only a handful of these covers made, for the 1937'ish Big Plunger Works race bikes.

These covers are copied from an original and look exactly the same. So, if you want to give your pre-war cammy that most exclusive look - they do not come much rarer or unusual than this! - they are also manufactured in high qualiity AZ91E heat treated magnesium alloy - so are suprisingly light when compared to the more normal alloy version of the same cover.

Note: in the photos these covers look slightly wet. This is the protective water repellent oil I spray them in before placing them in a plastic sealable bag. 3\16" BSF screws should be used for the rev clock fitting. Update November

01/03/2020 Update: We are pleased to be able another small batch of these magnesium alloy outer timing covers - this ribbed variety sold out very quickly when we last offered them 6 years ago.  However, sorry to say, the cost of magnesium alloy foundry costs has risen out of all proporting to normal alloy since that time.  We only use the best quality foundry (who cater to the motor racing and aerospace industry) - and all machining is by our regular CNC partner.  After machining we then fully re-chromate them - before spraying and packing in Duck Oil, so although not cheap, we believe they are a high quality item, reflecting that cost.  

This is the Works 'Smooth' type SOHC outer timing cover fitted to Norton International and Manx models from 1938 onwards, with provision for a rev clock - but this type are the rare 'Works' version in magnesium. 

This version is the sports\racing version that has a rev clock boss cast in (generally considered the most desirable type). This type was fitted as standard on pre-featherbed Manx Nortons, but was often seen fitted to Norton Internationals, if wanting to fit a rev clock.

These versions have been faithfully replicated from an original pattrn, even including the original casting number and inner webbing. However, this version is manufactured in magnesium, which is a replica of the ultra rare type occasionally seen on the Works bikes in the late 1930's-1940's. Being manufactured in heat treated AZ91E magnesium alloy, they are also very light when compared to their aluminium alloy counterparts!

These magnesium versions are re-chromated after CNC machining to provide protection to the machined faces. They come lightly sprayed in duck oil to ensure they do not corrode in storage. 3\16" BSF screws should be used for the rev clock fitting (which we can also supply).  However, if you wish to fit one of these but do not currently have a suitable rev clock, we also sell a very pretty stainless steel lasercut inspection cover, that can be fitted in place of a rev clock and also look the part. 

Note: in the photos these covers look slightly wet. This is the protective water repellent oil we spray them in before placing them in a plastic sealable bags.

3\16" BSF screws are used to attach the rev clock gearbox to the timing cover (Item 0974) and we supply a pair with every timing cover purchased. 

01/03/2020 Update: We are pleased to be able another small batch of these magnesium alloy outer timing covers - having sold out on the original batch quickly after we last offered them 6 years ago.  However, sorry to say, the cost of magnesium alloy foundry costs has risen out of all proportinon to normal alloy since that time.  We only use the best quality foundry (who cater to the motor racing and aerospace industry) - and all machining is by our regular CNC partner.  After machining we then fully re-chromate them - before spraying and packing in Duck Oil, so although not cheap, we believe they are a high quality item, reflecting that cost.  

This is the 'Ribbed' type SOHC outer timing cover fitted to Norton International and Racing International (early Manx) models up to 1938.

This version is the sports\racing version that has a rev clock boss cast in, which were available even in those early days, but as rev clocks were only just starting to be used in the mid 1930's these covers were only made in very small numbers and are now rare and highly desirable.

I was fortunate to have a friend who had one of these original covers and was able to lend me it so we could have patterns made to produce this exact copy.

These versions have been faithfully replicated from an original pattrn, even including the original casting number and inner webbing. They have then been CNC machined and for the aluminium versions they are bright polished and ready to fit.

3\16" BSF screws are used to attach the rev clock gearbox to the timing cover (Item 0974) and we supply a pair with every timing cover purchased. 

This is the 'Smooth' type SOHC outer timing cover fitted to Norton International and Manx models from 1938 onwards.

This version is the sports\racing version that has a rev clock boss cast in (generally considered the most desirable type). This type was fitted as standard on pre-featherbed Manx Nortons, but was often seen fitted to Norton Internationals, if wanting to fit a rev clock. These versions have been faithfully replicated from an original pattrn, even including the original casting number and inner webbing - from heat treated LM25TF alloy.

They have then been CNC machined and for the aluminium versions they are bright polished and ready to fit.

3\16" BSF screws are used to attach the rev clock gearbox to the timing cover (Item 0974) and we supply a pair with every timing cover purchased. 

We can also supply a pretty lasercut lozenge shaped stainless steel cover (Item 0325), should you wish to fit one of these covers to your engine, but do not yet have a rev clock for it.  We also supply rev clock gearbox's in various gears and rotations to fit this cover and your rev clock.

These are supplied polished, but as with the magnesium type, we also spray in light Duck Oil when they are packed.

Pair of cheesehead screws to fit Rev Clock gearbox to our SOHC Timing Covers

These screws are 3/16" BSW and fit our outer timing covers with rev clock boss - the covers are tapped and threaded with these threads.

Note that the original 1948 Norton Spare Parts Catalog shows there being nuts fitted to the rear of these screws - i.e. inside the magneto chain area.  My own recommendation would be to ensure that if you are also using nuts - that you use some form of threadlock or spring washer to ensure they do not work loose in use - and they do not foul the magneto chain sprocket. 

(personally - I prefer to use just the thread in the case and ensure the screws are inserted using threadlock).

The screws are slightly longer than required, as they will need to be shortened to fit the particular type of rev clock gearbox you are fitting.  These are plain steel cheesehead screws (not stainless).

This listing is for a matched pair of SOHC Inner Timing Cover and Outer Timing Cover with rev clock boss.  There are various combinations available and although this listing shows a single price of £450, dependent on the combination of magnesium or aluminium inner and ribbed or plain outer, the price will vary slightly dependent on what we have in stock, which we will confirm back when you order - but will be slightly cheaper than buying each cover seperately.

However, the benefit of buying both together is that these will have been linished and polished as a matched pair, so will pair up far batter.  As there were so many slight variations of covers over the years, when fitting unmatched inner/outer covers (even originals), there is always some small difference in matching that has to be linished out - but buying together as a pair like this means this will not be necessary.

Additionally, there is a slight saving in buying both together (although it actually takes more time to prepare them this way!!), and I include a pair of outer rev clock fixing screws with each purchase.

The following combinations available:

• Magnesium inner cover and Plain alloy outer cover
• Magnesium inner cover and Ribbed alloy outer cover
• Alloy inner cover and Plain alloy outer cover
• Alloy Inner cover and Ribbed alloy outer cover

For more details of the inner and outer timing covers, please see the individual listings in the Timing Case section (items 318 - 322).  Note: in the photograph the cover looks like it has a mark - this is just a smear of oil and the reflection of light from the camera - all covers are highly polished and then bubble wrapped.

When ordering this item - we will email you back with the actual price and availability of each combination - depending on what is in stock at the time

November 2021 Update:  Although some combinations have now sold out, we still have a few made up (see listings) - but if you do not see the combination you require available - email us on sales@racingvincent.co.uk for an update - we do have some unmachined inner timing covers we intend to make into the next batch at some point in the near future

This is a magnesium timing cover to fit SOHC M30/M40 Norton Racing Internationals (pre-war) and pre-Featherbed Manx Norton engines. As with all parts we produce, these castings have been maufactured to be as close as possible to the shape and look of the original castings, and even have the original casting number, in the same position as per original.

The patternmakers I use are excellent, and if I say so myself, the castings are virtually identical in shape and contour to an original - including the inner face and boss. In the second photograph here, you can see an original casting (upper) compared to my version (lower), which demonstrates how close to identical they are. They come with the oil pump drive bearing already pressed in and reamed, and this phosphur bronze bearing has the correct spiral turned oil groove running through it, which stops just before it reach's the outer face - a feature often overlooked, which if allowed to run all the way through, can result in excessive oil being fed into the magneto chain well. It is manufactured in A8 Magnesium Alloy and is substantially lighter than the normal LM25TF aluminium version.

Magnesium inner timing covers are supplied fully chromated (covers are re-chromated after machining to ensure ALL surfaces are protected) - the black chemical finish that protects the base magnesium from corrosion, a necessary precaution as this alloy suffers from oxidisation if left exposed to the atmosphere. They are also lightly sprayed in water repelling (Duck) oil before being placed in sealed bags, to further protect them from condensation in storage, which explains the 'wet' look in the photographs.

Which model specification would these have originally been fitted to?

 These would have been fitted to any SOHC Norton fitted with magnesium (M30/40 or Manx) type magnesium crankcase. They would have also been fitted to early pre-Featherbed type DOHC Manx engines. Normal production M30/Manx specification was to magnesium crankcase, magnesium Inner timing cover and aluminium outer cover - however some Works and Works supported engines were fitted with magnesium outer covers (which I can also supply). However these inner covers can also be fitted to aluminium International crankcases if required as the casting is the same (as per my Racing International).

Note: there was only one variety of magnesium cover supplied - the type with no breather hole.

This is an aluminium timing cover to fit SOHC Norton International, CS1 and pre-Featherbed Manx Norton engines - that were originally fitted without a breather hole (see also item 0318b for covers with breather holes). As with all parts we produce, these castings have been maufactured to be as close as possible to the shape and look of the original castings, and even have the original casting number, in the same position as per original.

The patternmakers I use are excellent, and if I say so myself, the castings are virtually identical in shape and contour to an original - including the inner face and boss. They come with the oil pump drive bearing already pressed in and reamed, and this phosphur bronze bearing has the correct spiral turned oil groove running through it, which stops just before it reach's the outer face - a feature often overlooked, which if allowed to run all the way through, can result in excessive oil being fed into the magneto chain well. It is manufactured in LM25TF Aluminium.

It should be noted that when ordering an Aluminium timing cover, these came in two standard types: Very early and very late covers were devoid of a breather hole (as per all magnesium timng covers), but for a period around the mid 30's to late 1940's (I think!), they had a breathing hole at the upper part of the bevel chamber.

This listing is for an aluminium timing cover WITHOUT breather hole.

Aluminium covers are supplied with the visible areas polished (but due to the intricate shape, I have refrained from obtaining an overpolished mirror finish, to avoid the increased risk of damaging the machined faces).

Note: After initial machining of this batch of timing covers it was found that with the variation in different original outer covers over the years, somes did not line up well. Therefore, the top threaded hole of the covers was bored out to take an oversize threaded insert, and then the 1/4 BSW" thread hole re-machined in a slightly different position, to make the fit more 'generic'. This insert has been expertly applied and is virtually invisible. It in no-way reduces strengh (in fact it makes the thread stronger, as it is of a higher tensile strength than the original casting material!), but it is mentioned for completeness.

The final photograph in this item shows an Inner Timing Cover, matched with an Outer Timing Cover - Sold Seperately

Update Aug 22: Sorry, we are now out of stock of aluminium SOHC inner timing covers.  Given current economic climate and rising costs - I am not likely to have any more made in the next 12 months at least.  However, if you do want one, please email us on sales@racingvincent.co.uk - if we have enough pre-orders, we may consider having some done.

This is an aluminium timing cover to fit SOHC Norton International, CS1 and pre-Featherbed Manx Norton engines, of the type originally fitted with a breather hole.

As standard the inner timing cases have been machined without the breather hole. However, I include a picture of an original timing cover inset to the main cover, that has this additional breather hole. If this catalog item is ordered then I have a jig to ensure the hole is machined into the correct position. If ordering this version of the Inner Timing Cover please bear in mind there may be a two week delay to allow for the cover to have the additional hole machined.

As with all parts we produce, these castings have been maufactured to be as close as possible to the shape and look of the original castings, and even have the original casting number, in the same position as per original. The patternmakers I use are excellent, and if I say so myself, the castings are virtually identical in shape and contour to an original - including the inner face and boss. They come with the oil pump drive bearing already pressed in and reamed, and this phosphur bronze bearing has the correct spiral turned oil groove running through it, which stops just before it reach's the outer face - a feature often overlooked, which if allowed to run all the way through, can result in excessive oil being fed into the magneto chain well. It is manufactured in LM25TF Aluminium.

It should be noted that when ordering an Aluminium timing cover, these came in two standard types. Very early and very late covers were devoid of a breather hole (as per all magnesium timng covers), but for a period around the mid 30's to late 1940's (I think!), they had a breathing hole at the upper part of the bevel chamber. This item is for a timing case WITH breather hole. Note - when ordering this item, there may be a delay of two weeks, to allow me to machine the additional breather hole into the cover. Aluminium covers are supplied with the visible areas polished (but due to the intricate shape, I have refrained from obtaining an overpolished mirror finish, to avoid the increased risk of damaging the machined faces).

Note: After initial machining of this batch of timing covers it was found that with the variation in different original outer covers over the years, somes did not line up well. Therefore, the top threaded hole of the covers was bored out to take an oversize threaded insert, and then the 1/4 BSW" thread hole re-machined in a slightly different position, to make the fit more 'generic'. This insert has been expertly applied and is virtually invisible. It in no-way reduces strengh (in fact it makes the thread stronger, as it is of a higher tensile strength than the original casting material!), but it is mentioned for completeness