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| | Bristol Aquila |
 | | During the compression and power stroke, the sleeve is at the top of its travel and its ports rise above the level of internal sealing rings in the cylinder head, which in the case of sleeve valves, are called “junk heads.” Two spark plugs near the center of the junk head provide ignition. |
 | | The Perseus, a nine-cylinder air-cooled radial with a bore of 5.75” and a stroke of 6.5” (1,520 cu in) was rated at 515 hp. |
 | | The Aquila, Bristol’s second sleeve-valve engine design, was patterned closely after the Perseus, but with smaller dimensions (5.00” bore, 5.375” stroke, displacement of 950 cu in). |
| www.enginehistory.org /bristol_aquila.htm (393 words) |
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