This item is for a pair of the distinctive 'conical' shaped valve spring cups, of the type that were fitted on OHV and Walter Moore CS1 Norton engines through the 1920's up to 1931. CNC machined from an original pattern, including radial holes (for the top valve cup) - these are designed to fit the early spring type (which we can also supply).
This type of valve cap are now extremely hard to find, this is possibly the first batch made since Norton Motors last made them . . . probably about 1931! They were fitted to both the Walter Moore CS1 engine as well as most OHV engines (to our knowledge) through the 1920's until approximately 1931 - when the coil valve spring and cup design was changed to a different design - where the inner spring almost touched the outer spring (which we also sell).
Sold as a matching top and bottom cup (they are sold as a pair as they cannot be used with any other type of Norton spring - they are specific to this earlier design), each pair of cups has been CNC machined to the original specifications (originals used as patterns), from similar material to original, and come with a black rust preventive finish applied. 2 Pairs are required per engine.
We can also supply the correct 1920's type coil valve springs - both the 500cc OHV/SOHC type (our Item no 0966) and the even rarer 596cc OHV spring (our Item no 0977), of which both types were copied from original patterns.
These are CNC manufactured to fine tolerance in EN8 steel, then black chemical dipped to protect from rust. Price is for a single matched pair (i.e. 2 pairs required per engine). As you can see - these are not cheap, but hope you will appreciate that the setup costs for a quite complex design, and small volumes means they are as competitively priced as we can make them (in reality - I doubt we will ever sell enough to get back the setup costs!).
Background and Fitting Information:
These conical type valve spring cups are designed to take the 1920's Norton valve spring design - where the inner spring was substantially smaller than the outer spring, both in outer diameter and length. Therefore it was necessary to design a top spring retaining plate which was conical in outer shape, to allow seating of both springs at very different points. Because of that spring design, it also necessitated that the inner section of the top valve cup is heavily concave and curved - and has 6 radial holes drilled in them to reduce the overall weight of the top valve cup. By the early 1930's (sometime in 1931 I believe), this design was replaced on both OHV and SOHC design by a pair of springs were the inner spring was taller and closer in diameter to the inner - I am told this could be because it was realised that having valve springs that touched was a better design.
As far as I can tell, these conical type valve spring cups were fitted to the following models:
- 1920's OHV Models up to 1931 : They are listed in late 1920's Spare Parts Catalogs as either part numbers 4060/4061 (top/bottom) or parts numbers 5131 (top). I cannot guarantee if this design was used on the very first OHV models (1922) - but assume they were, and would be glad to have that confirmed by any owner lucky enough to own one this early or thereabouts
- 1927 - 1930 Walter Moore SOHC CS1: Known as the 'Cricket Bat' engine because of its distinctive timing cover and bevel tube shape, this design of valve caps (in conjunction with our 0966 valve springs), were used on that engine - part number 4060/4061.
- 1930 1931 Arthur Carroll SOHC CS1: As far as we are aware, the very first Arthur Carroll SOHC engines (i.e. pre-cursor to the Interanational) also used this type of valve cup design, up until sometime in 1931. Although surviving engines may have been restrospectively fitted with the later design 'flat cup' to valve spring cup - we would be interested to hear from any owners of an original pre-31 Arthur Carroll engine fitted with this type of conical cups
Fitting information and parts interchangability: These valve spring cups, and our matching valve springs - 0966 and 0977 were all copied from original Norton patterns. Looking at the Spare Parts catalogs for the late 1920's, it is possible to see that the valve design for most of the engines had a pronounced 'Tulip' type valve head design. I have a drawing of one of these valves, and can see they are very similar in dimensions to the later Norton ES2 OHV valve which we stock - Item 0678.
You will see that in one of the accompanyning photographs we have assembled the top and bottom conical cups, along with valve spring 0966, our OHV collets (0675). G&S ES2 Valve (0678) and our ES2 Valve guide (0696). Unfortunately I do not have an original valve guide from a 1920's cylinder head, so I cannot confirm that the valve guide (0696) that we sell would have exactly the same chamfer for the bottom valve sring cup as an original 1920s valve guide - but it looks very close. If anyone has an original valve guide, I would be interested to confirm the chamfer - but please email us if you are ordering any of the parts above for your 1920s model and happy to confirm dimensions of our listed part's shown here - firstname.lastname@example.org.
We may consider making a batch of the tulip headed valves in the near future if enough interest - but I know of other owners that have fitted ES2 valves (our item number 0678) to their CS1.