Note that the tubular air intakes on top of the cylinders have no valves.
"The First Airplane Diesel Engine: Packard Model DR-980 of 1928"
Robert B. Meyer
The latter being tubular, dry more readily, uniformly, and to a denser consistence than they could otherwise.
"Peat and its Uses as Fertilizer and Fuel"
Samuel William Johnson
But the oddest of his actions was the manner in which he employed his long tubular trunk.
"Popular Adventure Tales"
Mayne Reid