8 Valves for the Road

It was clear from the earliest days of 4-stroke engine design that multiple valves in a cylinder head had clear advantages over just two; the valves themselves would be lighter, making an easier life for valve train components and valves less likely to break. It’s also possible to move more air through two (or more) small valves than one big one, as the total surface area of multi-valves could be larger than a single valve port, without risking a crack across the cylinder head from a weak structure with one mighty hole.  Smaller valves meant a lighter valve train, and higher revs for the motor, which meant more power and less wear, as it’s easier to shift heat away from many small parts than a couple of big ones.

Thus, in the ‘Teens and ’20s a lot of factories experimented with 4-valve single cylinder or ‘8-valve’ V-twins, especially in the racing world. Indian was first with their pushrod 8-valve twin racer in 1911, that dominated board track and dirt track racing for several years, but was a fairly crude and fragile design, with poor lubrication to its delicate valve train.  The Indian 8-Valve did well in European and Australian racing too, but to my knowledge, only one or two were ever converted to a road bike, as photographic evidence here demonstrates.

The 8-Valve concept was greatly expanded  in 1913 by Peugeot, who revealed a parallel-twin double-overhead camshaft racing motor with four valves per cylinder, based on their all-conquering Grand Prix racing car, designed by Ernst Henry and ‘Les Charlatans.’  The Peugeot 500M was raced at Montlhéry and Brooklands, and was fast, but not dominant like the water-cooled GP Peugeot cars.  It would take years of development after WW1 for it to become competitive, which required the loss of one camshaft and four valves!  Still, a remarkable technological achievement.  Sadly, none survive, and it appears none were ever used on the road.  Read more here in our article ‘The Lost Peugeot Racers.’

Harley-Davidson, finally interested in catching up with Indian on the race track after abdicating all factory involvement for years, revealed their own 8-Valve V-twin racer in 1915, and built several versions through 1927.  None to my knowledge were converted to road bikes in the day, although the rise of small-batch manufacturing of reproduction 8-Valve engines (both H-D and Indian) has broadened specialist builder’s horizons.  One such is Harry Hacker in Germany, who has combined both Peashooter 2-valve racing cylinders and heads with twin-cam JDH V-twin crankcases, making a powerful special with 70hp.  He’s also used replica 8-Valve cylinders and heads atop a JDH base, which is a fearsome beast indeed.

In Britain, an 8-Valve V-twin was produced commercially by British Anzani, who supplied engines for all applications, from aviation and boating to cyclecars and motorcycle.  The Anzani 8-Valve motor was designed by the Belgian Hubert Hagens, who had considerable experience in racing before joining British Anzani.  Company founder Alessandro Anzani was by then wrapping up his involvement in his several branches in England, France, and Italy, and retired in 1927 at age 50.  The Anzani V-twin was also produced in a 2-valve configuration, and sold as the Vulpine.  But for racing, and a very few road bikes, several manufacturers took the bait, including Montgomery, McEvoy, Croft, and Zenith, all of whom produced 8-Valve motorcycles in the single digits.  Those that survive (the cynical would say, more than were ever produced) are spectacular motorcycles, and extraordinarily valuable in their rarity and technical savoir faire.  All of these producers found 2-valve V-twins to be more reliable for regular use, but there’s no denying the appeal of such a fearsome engine in a hot road bike.

It should be noted that several British marques built 4-valve single-cylinder road bikes, like Triumph’s Ricardo (1921-24) and the Rudge 4-valve/4-speed line (1924-40).  Many specialist builders over the years have adapted these well-proven 4-valve cylinder heads onto V-twin engines of JAP or Harley-Davidson manufacture, with mixed results. The immediate increase in power meant of course, increased heat in the engine to deal with, and no direct lubrication to the valves until the late 1930s Rudge motors with enclosed valves.  The new-found power also exposed weaknesses in the clutch and gearbox (as Vincent-HRD found with their first OHV V-twin Series A Rapide in 1936), as well as the frame, forks and brakes, which were well adapted to a 24hp sidevalve V-twin, but not to 60hp from a far better-breathing upgrade.

And back in Europe, it appears the German Wanderer company built an 8-Valve V-twin motorcycle in the mid 1920s. The cylinder heads are closely based on the Anzani pattern, but retain Wanderer’s distinctive horizontal finning.  This machine was spotted at Rétromobile in 2011, and I’d love to know more.  How many other companies built 8-Valve V-twin in the 1920s?  I’d love to know about more obscure examples: it Italy Moto Guzzi built the C4V 4-valve racing single, for example, based on their 1921 prototype designed by Carlo Guzzi: clearly the concept was explored in many countries.

Today’s tinkerers adding 4-valve cylinders and heads to antique V-twin motors are hardly alone, as the game is an old one. Way back in 1924 the Excelsior importer for Belgium, a Mr Taymans, decided to fit a pair of Triumph ‘Ricardo’ 4-v cylinder barrels and heads atop an American Excelsior V-twin, making a very handsome road-going OHV roadster, the ‘American-Excelsior-Triumph’. According to The Motor Cycle magazine, he built several of these beasts, although this article is the only evidence I’ve seen of one…have any survived?

From The Motor Cycle, July 24th, 1924:

AMERICAN-EXCELSIOR-TRIUMPH

An American V-twin Fitted with British Four-valve Cylinders

Something new in ‘hybrids’ has been evolved by Mr. R. Taymans, a well-known motor cyclist and motor cycle agent of Brussels.

Agent for the American Excelsior, he has a great admiration for the strength, rigidity, and excellent steering qualities of this machine; he has also an equal admiration for the productions of Britain.  So he has manufactured an eight-valve American Excelsior, employing two four-valve 500cc Triumph cylinders adapted to the Excelsior crank case.

Standard Parts

With the exception of a slight alteration in the cams to produce greater efficiency, entirely standard parts are used, and the only structural alteration has been the dropping of the engine almost two inches in the frame.  The standard Schebler carburetor is fitted, and with it the machine will do 78mph; this is increased to 82mph with a three-jet Binks.

According to the constructor, the acceleration is terrific.  Altogether, the machine has been on the road for a full year, and with a sidecar.  It is not purely an experimental machine, but is actually on the market, many of them having already been sold all over the continent of Europe. Complete with electrical equipment, the machine is priced at £132.  Mr. Tayman’s firm is Taymans Fréres, 641, Chausée de Waterloo, Brussels, Belgium.