Technical information on our 20-Horsepower Piston-Valve Steam Engine

20-hp piston valve V-twin steam engine
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This two-cylinder, 20-horsepower, 3 x 4-inch, double-acting, 90 "V" engine is designed in the simplest possible form for steady-state power production.

It will produce 20 hp with a maximum of 200 psig @ 700 rpm. It is well balanced for those parameters and is designed for self-starting. Its low-speed torque is in the order of 200 ft-lb and should be handled carefully.

It has very large balanced piston valves that will greatly increase its efficiency and can stand a considerable amount of superheat. Its nominal cutoffs are 55% admission and 65% exhaust. Cylinder clearance volume is in the order of 12–13% and will allow for moderate compression, which helps in starting the engine from cold. Admission starts at 1% before dead centers to aid in high-speed running with the standard 55 eccentrics.

This engine is not equipped with reverse or variable valve timing. Power can be increased by changing the eccentric angle to 60- 65, but this also decreases engine efficiency.

This engine has a drip valve on the bottom of each valve bore to augment getting rid of condensed water when the engine is started from cold. Hydraulic lock and damage can occur when a piston-valve engine is started carelessly from cold.

The two-cylinder "V" engine design was used with great success for small engines by Abner Doble and by Bill Besler in his famous steam-powered airplane. It is the simplest and lightest configuration for a two-cylinder engine and requires only two crankwebs and a crankshaft of only five parts. The intake and exhaust manifolds are not included. Motor mount brackets can be made out of 1-1/2" steel angle iron 18" to 24" long and bolted to the two bottom " holes in each end plate.

It is advisable to mount a 8 to 10-inch pulley on the CW mainshaft for hand rotation to ease starting the engine Add approximately one quart of MOBILE SYNTHETIC 30-40 weight air compressor oil to the crankcase, view the level in the crankcase sight glass. This oil will not solidify if water/steam were to enter the crankcase. Regular synthetic oil can be used. Connect low-pressure air to the two steam inlets in the two blocks and the engine should run nicely. It would be wise to recheck the valve timing and make sure that the admission to both the piston top and bottom are about equal. Correct valve timing is most important. Install an engine oiler before running on hot steam.

ENGINE OILING— On occasion open the bottom drain plug and see if any water has accumulated in the bottom of the crankcase. If so, let it run out, and then reclose the drain plug.

Before operation, make sure the oil level is visible in the sight glass. This engine requires steam cylinder oil injected into the steam line to protect the valve and piston from wear. MOBILE ONE synthetic oil of 400 viscosity is recommended, as well as any steam cylinder oil. The feed rate should be in the order of 1 quart per every 50– 60 hours of operation with highly superheated steam.

If you do not understand some of the terminology concerning the technical information relating to this engine, we suggest you order our Special Steam Package and study it. The concepts are not that complicated.

Please do NOT call, write, or e-mail for an explanation. If you’re not willing to do your homework, please don’t ask us to tutor you. IF you have a question AFTER you have studied our Special Steam Package, please call.


Our engines are guaranteed for two (2) years, parts and labor. Our engines should last a considerable longer time than that. However, the engine bearings and the piston rings may have to be replaced after 8,000 to 10,000 hours. At full power, a modern automotive engine will last only 50 to 100 hours

The warranty is voided if you don't lubricate the engine, if you run it at pressures and speeds beyond what we specify, or if you do something else demonstrating a serious lack of intelligence--like dropping it out of a second-story window.

30-day money-back guarantee if you return the engine in undamaged condition. There is a $750.00 restocking charge.

We have been making the smaller 1 and 3 horsepower steam engines since 1998. In that time, we have had one steam engine we have had to do warranty work on. The casting on the steam chest had cracked. We replaced it at no cost to the owner, even though the warranty had expired.

Information on our 20-Horsepower Piston-Valve Steam Engine

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This page was updated on 5 November 2011