H. Ricardo had a special predilection for the sliding cylinder valve system.

-In 1927 he made a variant, the E55/4 engine that gave 65 HP with four cylinders.

-The valve mechanism was the one mentioned Burt-McCollum system with the stroke and bore of the same measurement, that is, a "square" engine.

-It was used for trials and tests before authorities. One of the applications was as a starter motor for the main engines on the English R101 airship.