Legal Eagle Plain Engines

Better Half VW 2 Cylinder Engine

The Dual Mikuni Carb version of the Better Half VW

Legal Eagle™ and Legal Eagle XL™

The Better Half VW Engine has gone under some revision since the original 1993 version. Several improvements have resulted in greater power and reliability in the dual carbs, and other changes have reduced the complexity of the building. Here are several photos of the new engine. The plans you will receive are for this engine version, the only recommended version for the aircraft. The current design provides roughly  30 HP and will cost between $1,500 and $3,000, depending on your scrounging ability.

How the Better Half VW Engine got its start

Many years ago, there was a set of plans sold at Oshkosh for a ½ VW engine.

I bought a set, as I had been looking for a small engine I could use on my guppy I had just built. The plans called for the crankcase to be cut in half and a plate bolted on the back.  I built the engine and found that everything I cut off, had to put back on.

With those plans, the first thing that is cut off is the engine mount. The VW case uses these as the mounting holes for the car transmission.  Cutting the case calls for the builder to fill in a couple of half circles where the back cylinders had been. Also, on the bottom of the case, the oil drain hole is cut in half making it hard to deal with.  This created lots of extra work. The engine ran hot, and I had to add an oil cooler.  There was a lot of extra crankcase pressure to deal with.  Reed valves were added to deal with that problem.  I could see that this cut case design had lots of problems.

For the next engine I built, I used the case uncut.  I just covered the back cylinder holes with a 1/8” aluminum plate.  This engine ran cool and had very little case pressure.  Also, it weighed the same as the one I had cut.  This was due to everything I had to add back on the cut version.  There is just no advantage to cutting the case.  

I call my version the Better Half VW.  Since the engine turned out so good, I decided to sell the plans.  I used the words “Don’t Cut That Case” on my calling card and for ads in Sport Aviation magazine.  Several thousand sets of plans have been sold.

The gentleman who originally sold plans at Oshkosh called me several months ago.  In the conversation, he revealed that he had built only one engine, and he said the engine shook so badly that he never built another one. He also bought a set of Better Half VW engine plans from me.


Between 450 and 600 of these engines-conversions have been built and are flying today… Including dozens on flying Legal Eagles™, many featured at Oshkosh.

VW 4 Cylinder Aero Engine

1600cc VW Aero Engine

Double Eagle and Cabin Eagle

The Engine for the Double Eagle™ and the Cabin Eagle™ starts as the 1600ccVW engine that was in so many Beetle VW autos. It is identified by the two oil pressure relief valves on the bottom, one in front and another in the rear. The conversion to an airplane engine for the Cabin Eagle™ and the Double Eagle™ consists of 92mm cylinders, a zenith carburetor, an exhaust system, a carburetor heat system, and a Kubota tractor alternator. This is a mild hop-up and is very reliable.

Note: the scops to cool the rear cylinders. The carburetor heat system is covered in the plans, as are all the Engine attachments. Also, the video covers the engine assembly.

Briggs and Stratton Engine


Legal Eagle™ and Legal Eagle XL™

The engine has exceeded our expectations with its performance and smooth running. The engine is the type that they use in zero-turn lawnmowers. They roar all day long and give good service. The parts are inexpensive. Instructions for overhaul and maintenance are readily available on YouTube and from the factory. The reduction drive allows the use of a slower-turning large propeller-driven with a lower-powered engine.

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