Late 1920's - 1930's OHV/SV Cylinder Base Nut (Stainless Steel) - Each

Product no.: 1134 9003

In stock

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This distinctively styled Cylinder Base Nut was of the design fitted to OHV singles, before the OHV design switched to 'Through Type' long cylinder studs in approximately 1935. They were also used on Side Valve engines - both types employing a coarse Whitworth cylinder stud thread

Price is per stud.  Normally 4 are required per OHV or SV engine.

Background and Model Fitment:

We have CNC machined these nuts from stainless steel, using an original 1931/32 OHV Base Cylinder Stud Nut as the pattern - which can be seen in one of the accompanyning photos.  They have a coarse 3/8" BSW thread, a deep hex (ideal for getting a good ring spanner on), a wasted shoulder where it secures to the barrel base flange, and a distinctive shallow curve to the head, as many Norton nuts do.  Being of stainless steel - as well as not rusting, they greatly improve the appearance in the prominent barrel area.

It is difficult to be definitive about which models used this exact pattern nut - but a picture of it showing in the 1934 Norton Spare Parts Catalog is shown in the accompanying pictures - where it is described as Part Number 9003, and shown as being fitted to Models 1, 16H (side valve), 18, 19, 20 and ES2 (OHV engines) for that year.  In the later 1937 Norton Spare Parts Catalog (by which time the OHV engines were using full cylinder/head studs), Part Number 9003 is still being listed - but by this time indicating it was only being fitted to Side Valve engines, as you would expect.  Again, the 9003 nut appears again in the 1939 Spare Parts list, showing it was still being fitted to Side Valve models of the 1938-47 design.

For Post 1948 Sidevalve engines, it is difficult to be clear if the same shouldered nut was still being fitted - as the picture shown in postwar Spare Parts Catalog is unclear, and the part naming system changed - however, the same 3/8" BSW Whit crankcase studs were still being fitted, so will let you decide if you wish to use these on a Post 48 sidevalve engine. 

Late 1920's OHV and Walter Moore CS1 engines:  A similar nut - Part Number 4069 is described as being fitted to the ES2 Model in 1929 - but it is difficult to tell if it is identical.  The important dimension for this nut is that it has a 3/8" BSW Coarse thread (unlike most cylinder nuts, which used fine threads) - therefore if you have an early OHV engine using this thread - then this should fit.

Finally, it should be pointed out that the Walter Moore CS1 engine also used a similar Cylinder Base Stud.  Some catalogs of that era show a different nut being fitted to the CS1 engine, but it is difficult to be definitive.  However, if you have 3/8" BSW studs protruding from the crankcase, then again these should fit.

Email us on if you require more information to confirm these are correct for your engine.


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