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Safety notes:

Engine conversions must be carried out by qualified technicians and/or persons who will follow all safety guidelines as contained in pamphlets NFPA 54, 58, 38 or any other publication or guidelines stipulated by local, state or federal agencies and the authority having jurisdiction.  As a starting point, contact your local fire department, propane supplier and insurance company for guidance.  They will be able to direct you to the correct local governmental department for additional state and local requirements.

The manufacturer of these kits reminds us that they are NOT approved for use indoors use!

For information on propane safety, publications may be ordered through The National Fire Protection Association at http://www.nfpa.org.

A partial list of applicable publications are shown below:

• NFPA 37: Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines, 1998 Edition
• NFPA 54: National Fuel Gas Code, 1999 Edition (National Fuel Gas Code provides safety requirements for fuel gas equipment installations, piping, and venting.)
• NFPA 58: Liquefied Petroleum Gas Code, 1998 Edition. (Standard for the Storage and Handling of Liquefied Petroleum Gases, which provides the standard for the installation of the propane storage tank and piping to the first stage pressure regulator.)

OK, so what's involved in making an engine run on propane?

The existing carburetor on the engine must be modified to deliver propane into the combustion chamber.  It sound simple, and it really is.

Basically, instead of delivering vaporized gasoline as the engine sucks in the air/fuel mixture during the "intake" cycle, the carburator delivers a propane/air mixture.  The engine itself is not modified in any way.  It still sucks in the air/fuel mixture, compresses it, ignites it and converts the resulting explosion (internal combustion) into rotary energy during the power stroke.  Thus delivering work energy to the item which requires power (to rotate a generator armature for example).

The waste products are still expelled in the exhaust stroke, and the process continues, over and over.  It's like using little controlled explosions to rotate the output shaft. Suck it in, compress it until it's explosive, blow it up, and use the explosive energy to rotate the output shaft.  That's the way an engine works!

OK, enough said... A propane conversion just swaps one kind of fuel for another, and the other principals are the same.

So how does a conversion kit work?

We contacted the experts in carburetion and asked for help!  They said, "been there, done that, been doing it for years." The key is a vacuum controlled flow rate regulator, linked directly to a modified carburetor.

This conversion kit works because the air/fuel mixture is automatically adjusted as load changes are made.  This automatic adjustment is only possible because this special flow regulator is linked by a vacuum hose to the carburetor itself.

This allows the flow regulator to automatically sense changes in engine intake vacuum which is directly related to engine load changes.  So, if more load is added, the carburetor throttle changes, which causes an increase in intake manifold vacuum.  And this vacuum causes the flow regulator in the propane conversion kit to increase fuel flow to keep the air/fuel mixture ideal.  Without this feedback, it's impossible to keep the fuel/air mixture ideal and the motor running!

At the heart of the conversion is the modification of a carburetor to deliver the alternative fuel, and to provide a feedback method (a port to the vacuum inside the carburetor) to an external propane fuel delivery flow regulator, which is designed to accept the vacuum feedback and adjust the fuel delivery flow rate.  This special vacuum flow regulator is like having an extra hand automatically adjusting the regulator output knob, keeping the air/fuel mixture ideal!

As with all of the Tip of the Week episodes here at TheEpicenter.com, we have tried to be technically correct in our discussion. As always, I'm sure we will be corrected here or there, but what I'm trying to get across is that the conversion is fairly straight forward.  The most difficult part of the conversion is drilling one hole in the carburetor.

So without further delay, lets talk about what's involved in converting one of these engines with an off the shelf conversion kit to run on propane.

The steps are best described in a series of photographs.
The photos shown are for a specific model of carburetor but the modifications are similar on all carburetors.

Step One.

Remove the float chamber and plastic cap over vacuum fitting location.

Step Two.

Remove the Gasoline jet, float, and fuel shut-off valve.

Step Three.

Enlarge the location of the fuel delivery jet to accept the new propane jet, and seal unused passages.

Step Four.

Install propane delivery jet, and seal unused vents and air passages.

Step Five.

Seal unused gasoline fuel inlet.

Shown below are the spare parts from the original carburetor that are not required.

Toss the extra parts.

What does it look like when things are hooked up?

Here the system is shown before being installed on an engine (for clarity).

The modified carburetor is connected via two hoses to the vacuum controlled flow regulator.  The hose connected to the bottom of the carburetor delivers propane or natural gas to the new jet.

The second, smaller hose is connected to the side of the carburetor where the vacuum fitting has been installed.  The other end connects to the vacuum control feedback port on the flow regulator.

The third hose connected to the vacuum flow regulator could either be connected to the low pressure household feed for natural gas use; or, with the a portability tank kit, it can be connected to a portable propane tank using the special 12 PSI regulator included with the portability kit.

Shown here is the motor and flow regulator mounted on a pressure washer cart, and a close up of the flow regulator connected to the carburetor. The next shot is of the completed project.

In this project we used our direct drive alternator bracket and couplers to connect a 93 amp GM alternator and charging cables to the propane powered motor.

Some common questions and answers:

Q. Where can I buy a kit like this?

A. We don't sell kits, but there are many companies that do.
The best thing to do is use our search tool  and enter "propane conversion" and the brand of your motor. Like this: Briggs & Stratton propane conversion kit

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