Edward Turner’s Triumph

[John-B]

Which Triumph motorcycle was Edward Turner’s design with a V hemi-head engine that formed the basic design of the V8 SP250 and Majestic Major engines?

I was told a long time ago that it was a Triumph 600cc V twin but someone today said that wasn’t true as Triumph made a parallel twin and a vertical twin (whatever that is). Perhaps the 600c V twin rumour is wrong.

[Radford Jim]

That’s correct, the Triumph V twin was a vertical or parallel twin, not a V as the V8. From Wikipedia:

“For 1959 Turner designed the hemi-head Daimler 2.5 & 4.5 litre V8 engines used in the Daimler SP250 sports car and Daimler Majestic Major respectively. The valve gear was more similar to the Chrysler Hemi than the Triumph motorcycle, itself based on Riley”

I think the confusion is caused by the V for vertical! The two cylinders are side by side on a common crankshaft. On a 360° crank both pistons rise and fall together. On a 180° crank pistons are 1 up 1 down.
Hope this helps.

[John-B]

Thanks. When I go to shows I often say that the Dart engine was based on a Triumph motorcycle V 600 engine but I’ll now have to qualify that by saying that V stands for vertical V, not a V shape!

Also that Turner used hemi-head pistons but he wasn’t the first because Chrysler had already used hemi-heads.

[John-B]

After a little more Googling, it seems that the Triumph bike that was most likely used as the basis for the Dart was the Speed Twin, but that was a parallel twin 500cc on Wiki https://en.wikipedia.org/wiki/List_of_Triumph_motorcycles so was this really the basis for the Dart?

This website https://www.classic-british-motorcycles.com/1948-triumph-speed-twin.html says that it was a vertical twin 500cc, so I’m even more confused.

Did the 1948 Speed Twin have hemi-head pistons so that the piston design rather than the engine layout was the real basis for the Dart ?

[HyperSPace]

There have been several ‘engines with hemispherical combustion chambers produced over the years, possibly the earliest being the Welch Touring car of 1903. Chrysler never claimed to have invented the ‘Hemi’ engine but they were the first to put into mass production – and they’ve patented the name ‘Hemi’, so be careful how you describe the Daimler version!

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