8-VALVES FOR THE ROAD

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A lusty 1000cc V-twin from 1924, with 8 valves up top, in an Anglo-American hybrid

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.

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The granddaddy of all 8-Valve motorcycles, the 1914 Peugeot 500M 500cc parallel-twin 8-V DOHC racer (see story here)

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 an 8-v twin racer in 1912, followed soon after by H-D, while across the pond, Triumph and Rudge were building 4-valve single-cylinder bikes, while Anzani had an 8-v twin.

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1924 McEvoy 8-V V-twin racer with Anzani engine, as seen at Vintage-Revival Montlhery in 2013 (see story here)

Today, original 8-valve V-twins from the Vintage era are pretty near the top of the collectible heap, but lovers of performance, and hot-rod Vintage motorcycles, still experiment with installing modern reproduction 8-v cylinder heads onto 'J' series Harley crankcases (as per my post on Harry Hacker's Harleys), and the same with Indian products.  A few have experimented with Rudge 4-v cylinder heads atop JAP crankcases, which sounds fun too, although all these experiment suffer from the same afflictions of the original 1920s designs; inadequate top-end lubrication, and a strain on components due to a sudden and significant increase in power!

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One of Harry Hacker's compelling experiments adding a pair or reproduction 8-V cylinder heads to a Harley JD bottom end. (see story here)

In their experiments, today's tinkerers are hardly alone, nor are they the first garagistes to DIY an 8-v engine.  Way back in 1924, it seems 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?

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A Triumph Ricardo with 4-valve cylinder head, produced from 1921-28

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A much later Triumph with 8-V cylinder heads - the prototype for the TSX model, with special Weslake cylinder heads...a parallel twin like the 1914 Peugeot, but even 60 years later, the French machine's DOHC spec was too advanced for Triumph!  (read more here)

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A pair of c.1912 Indian 8-V cylinder heads, offered on eBay of all places, several years ago (read the story here).

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A 1929 Harley DAR 8-valve racer from the Wheels Thru Time Museum, seen at the Pebble Beach Concours in 2010 (read more here)