A Monovalve Diesel Engine

| October/November 1994

  • Monovalve Engine
    Monovalve Engine, illustration by W. Bryce.
  • Manifold side of Monovalve 4-75
    The manifold side of the engine showing the low restriction exhausts and inlet which appears to get some sort of assistance from a flywheel fan.
    Ted Paproski.
  • Marine Monovalve 4-75
    Ted Paproski's marine Monovalve 4-75 which is so well balanced that he ran it just the way you see it without being anchored down.
    Ted Paproski.
  • Monovalve illustration
    Monovalve illustration from High Speed Diesel Engines, Part 1.

  • Monovalve Engine
  • Manifold side of Monovalve 4-75
  • Marine Monovalve 4-75
  • Monovalve illustration

67 Albion Road Ashburton, Victoria 3147, Australia

Ever seen a side valve Diesel engine with only one valve per cylinder? Warwick Bryce describes one that was made in America during the early 1930s, when diesels were still going through their evolutionary stage.

Mention of the preservation of a Monovalve diesel engine in the Reflections column started me looking through old engine books, and I turned up quite a bit of information on this unusual engine that uses only one valve per cylinder:

The Designer

In the mid 1930s the Monovalve 4 cylinder diesel engine was made in Oakland, California by the American Diesel Engine Company. Its designer and manager of the company, Charles A. Wins-low, claimed 30 years engine building experience had enabled him to design a unique engine that embodied the best marine engine features.


It was a 4 cylinder water cooled vertical engine suitable for stationary, marine and use in tractors and trucks. Power was rated continuously at 75 HP @1200 RPM with an intermittent rating of 125 HP @2000 RPM. Bore and stroke of 5 by 7 inches gives a displacement of 665 cubic inches.


The engine is of side valve layout but has only one valve per cylinder that handles both inlet and exhaust. A simple casting forms the cylinder head that has an injector squirting almost horizontally into the combustion chamber that is formed in the underside of the head and is half over the valve and half over the piston. Injection equipment is conventional Bosch plunger pump and pintel type injector set at relatively low 82 atmospheres. A large diameter exhaust manifold with a venturi shaped entry fits over the much smaller exhaust port. An inlet manifold communicates with the exhaust manifold at the entry to the venturi.

7/28/2018 3:41:59 PM

Just tripped across this and will mention a recently seen PACKARD 7 cylinder (I think) radial air cooled single overhead valve diesel that flew in the mid '30's. Some small number were made and much info is available on the NET.


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