Purchase your engine as late as you can. The longer you store the engine, the more susceptible it is to corrosion, damage, or obsolescence. You’ll need to have an engine to build the cowling, but if you are lucky enough to have access to a core, it will do just as well as an airworthy engine. There are some benefits to deciding on an engine plan early, such as being prepared for purchase if a good deal comes along, and planning the supporting systems accordingly.
Bob Barrows designed the Bearhawk around a 4-cylinder angle valve Lycoming O-360 that produced around 170 horsepower. His second prototype used the parallel valve Lycoming O-540 producing around 235 horsepower, in part just to see how it would do. The airplane is a great performer with the smaller engine. With the larger engine, it has been described as “barbaric.” There is a natural tendency to think that bigger is better when it comes to engines, but this is not always the case with airplanes. Don’t let your ego make the decision. Bigger engines are heavier, and often require additional system requirements that further compound the weight gain. Read more about this topic in the Bingelis books. Bob prefers to see the engine weight kept under 400 pounds. Continental 0-470/520 engines weigh a little more than that, so he has adjusted the design of the motor mounts for those engines.
To oversimplify, here are some rules of thumb: if you live in a place like the western United States where you’ll frequently be climbing to density altitudes above 10,000 feet, or if you’ll be regularly flying at weights above 2200 pounds, lean towards the larger engines. If you’ll not be regularly needing these kinds of performance demands, you can save around $10,000 in initial cost and 100 pounds of empty weight by using a smaller engine. Ongoing cost savings will include reduced fuel burn during takeoff and climb and reduced maintenance needs of the 4 vs 6 cylinders. Both configurations will burn essentially the same fuel in cruise at the same airspeed, but if you cruise both at a high power setting, the bigger engine will deliver around 15-20 extra knots for 3-5 more gallons per hour. Back at 65% power, the average fuel burn of a 540 is approximately 12.5 gph, versus 9 gph for the 0-360.
Drag increases noticeably with speeds above around 115 knots, and the resulting miles per gallon will reflect this.
Regardless of your choice, be prepared for a dizzying number of variants, some of which may seem like a bargain. They may indeed be a bargain, or they may be something totally unusable that will be expensive to reconfigure. The safest bet is to stay near the center of the envelope, so to speak. Here are some tips to help you narrow down the choices.
Consider what you’ll need for accessories, since this may narrow down the engine choice. Although not a requirement, a constant speed propeller is highly recommended, and will make it possible to better utilize both ends of the airplane’s speed envelope. If you plan to run a constant speed prop from the beginning, or if you think you might like to ever install one, consider this in your engine shopping, to ensure that you have the appropriate provisions for a prop governor and a hollow crank.
Many builders consider mounting an alternator on the vacuum pump drive pad. These alternators are available in a range of sizes and can serve as a backup to a front-mounted belt-driven alternator, or as the only alternator. Your choice here will determine whether you’ll need to have a vacuum pad and drive.
Most carbureted Bearhawks use gravity fuel systems. As designed, the system delivers adequate flow for engines in the recommended range, and will not require an engine-driven fuel pump. Builders choosing fuel injection will require an engine-driven fuel pump and the associated provisions in the accessory case, and likely other components aft of the firewall.
As far as ignition is concerned, there seems to be a consensus to avoid the varieties with a single magneto drive. Beyond that, builders have used traditional mags as well as the experimental electric options with good results.

Choosing a 4-Cylinder Lycoming
First, limit your search to those with Type I Dynafocal mounts, since these are the only ones that will fit the engine mounts provided by Bearhawk Aircraft. Bearhawk Aircraft does not support conical mount engines.
Some builders shop in the 0-320, 150/160 hp size, but those builders must pay particular attention to keeping the airplane light. Kept reasonably light, the overall performance will be better than a C-172 by a measurable amount.
The 180 hp 0-360 engine is probably the best choice for 90% of BH builders. It is available new from Lycoming (with special OEM pricing for kit builders), in various experimental engine kits from other suppliers, and is ubiquitous in its use in many applications. Some of the alternatives include Superior and Continental (which has recently bought ECI/Titan).
With 170-200 HP, the takeoff and climb performance will be on par with a Cessna 182, although cruise will be lower, around 110-115 knots. The wide deck and narrow deck options are both acceptable, but look to the angle-valve variants rather than the parallel valve. These engines would have been fuel injected in their original configuration, but with guidance from Bob many Bearhawks have flown with these cylinders and a carburetor. When Bob builds an engine like this for the 4-place Bearhawk, he uses a rear-intake sump and makes a special 90-degree adapter to move the carburetor aft. This puts the carburetor in about the same place as it would be for a 540, and makes the exterior intake much more streamlined. This is possible because the 4-cylinder engines leave cavernous space between the engine and the firewall, since the prop mounts at the same station regardless of the engine. Within the 360 variants, the final horsepower will be determined by the compression ratio. This will also determine the minimum fuel grade. A ratio in the 7:1 neighborhood will deliver around 170 hp with the ability to run 87 octane fuel, assuming you can find it without ethanol. Ratios near 8.5:1 will deliver around 180-190 hp with the ability to run ethanol-free 93 octane fuel. Higher ratios will require 100LL, but will deliver closer to 200 hp.
Adding fuel injection makes it an IO-360. This adds weight and complexity, and will provide a slight power increase.
There are a few 4-cylinder variants that increase displacement and horsepower. One is the IO-390, which produces in the neighborhood of 210 hp for a cost premium of $15,000-$20,000 over the angle-valve O-360. This variant has flown successfully in multiple Bearhawks. Another is the Titan IOX-409, which is rated for an astounding 230 hp, but at an equally astounding price. They also offer the 370 and 375 “Stroker” engines, which have parallel valve cylinders making 185 – 190 HP with a carb and 195-200 HP with fuel injection. With any engine choice, but especially with the less common choices, it may be beneficial to talk with a Bearhawk builder who has successfully implemented the design, which will help identify any required deviations from the basic configuration.

Choosing a Six-Cylinder Lycoming
The 0-540 series of engines are heavier, but provide an increase in overall performance that is hard to believe. However, nothing is free, as the useful load will go down at least 100 pounds. Experience shows that it may go down as much as 200 pounds if the larger engine inspires the builder to also install auxiliary fuel tanks (30 pounds), fuel pumps, etc. Choose a parallel-valve 0-540, not an angle-valve. The angle-valve engines weigh over 80 pounds more than the others. Whether it is a wide deck or narrow deck engine makes no difference. You’ll find variants producing 235 hp, 250, hp, 260 hp. 235 hp engines (“B” series) are lower compression engines capable of burning automotive fuel. They are cheaper and easier to acquire, and performance is still unbelievably good.
Hartzell constant speed props can only be used on O-540 A4XX, 0-540-B4XX, -J3XX engines. All other series of 540s, which are usually early engines, must be modified with heavier crank shaft counterweights or use a McCauley prop.
All 540 Lycomings can be easily modified with the heavier counter weights. They can be installed without disassembling the engine, by removing cylinder No. 6. The parts and instructions are available from: Johnston Aircraft Svc, Inc, P.O. Box 1457 Tulare Municipal Airport, Tulare CA 93274, 559-686-2161, www.johnstonaircraft.com.
There are two types of mount ears on 0-540s. The Type I has 1 3/8” holes the Type II has 2” holes. These determine which motor mount you’ll need from Bearhawk Aircraft, and which motor mount rubbers to buy. The mount lugs bolt to the engine case, so they are interchangeable, but expensive.

Continental 360/470
The six-cylinder Continental 0-470 engines represent good buys on the used market and are smooth running, well known engines. They are usually heavier than 0-540 Lycoming, and use McCauley props. The output will vary from 215-285 hp, depending on the output. The IO-470 is 260 hp, but there’s the probability of firewall interference with the longer fuel handling unit at the rear so it’s not recommended. The basic cowling design was for the Lycomings, so modifications will be required. These engines use an entirely different mounting strategy, and variants other than the O-470 will likely require custom mount fabrication. We say that the O-520, being heavier than the O-470, which is heavier than the O-540, is not a viable engine for the Bearhawk.

Automotive Engines
Bearhawk Aircraft does not provide any support services for automotive conversion, so you’ll be designing your own motor mount, cowling, etc. You are building your own airplane, and it is your experiment. It is your own choice to make, but consider the following. The automotive engines can seem seductive. What’s not to love about an initial price that is 1/10th that of a Lycoming? Traditional airplane engines were designed many decades ago, so surely there is the technology for making better engines now? Sometimes a builder starts down this path and feels like he has stumbled upon a secret alternative that nobody else knows about.
The big issue with auto engines is that we must not just consider the engine, but rather the overall task of powering the airplane. We often hear in hangar discussions that airplane engines are really simple. In some ways, they certainly are- but in many ways, they are not. Every aspect of their configuration has been carefully considered and engineered over decades of use. Design choices are not arbitrary- they are almost all based on making the most reliable overall powerplant possible, applying lessons learned from failures large and small. The same applies to engines designed for cars, perhaps even to a greater degree. The folks at Subaru have painstakingly engineered every detail of their engine, how it relates to every other aspect of the car, and how it is used in that application. But how does that application relate to the airplane environment? Airplane engines are designed to run near their maximum RPM for hours at a time. Car engines are designed to operate at maximum RPM for only a short time. When it comes to cooling, the airplane engines applicable to the 4-place Bearhawk are air-cooled. Most car engines are liquid-cooled, and are going to require a radiator. Where is that going to go? The airplane engines are direct-drive, turning the prop at the same RPM as the crank. Will the auto engine be able to deliver the performance you’d want in that configuration, or must it be geared down? How is fuel to be metered, and ignition to be delivered? How robust are those systems, and what is their failure mode? Do those devices give warning of failure before they completely quit? What kind of propeller choices are going to be available for the car engine? How hard is it going to be to service the airplane custom components when you are away from home and have a problem? What about insuring the plane when it is time to fly? What about resale value?
All of these questions get to the broader goal of providing a total powerplant solution. Mounting, cooling, fuel metering, intake, ignition, exhaust, and power transmission may sound like just a few little things to sort out, but experience shows that these are actually really big things to sort out. An auto conversion adds at least a year to the construction time, apples to apples. The majority of Bearhawk builders who have stuck it out and flown with auto engines have later switched to traditional airplane engines after their plane was flying. There are one or two notable exceptions, and for anyone still considering an auto engine, we strongly encourage you to get in touch with one of them.

Propeller Considerations
Most people use a constant speed propeller on the airplane, though it is not a necessity. A fixed pitch prop will save around thirty-five pounds and many thousands of dollars.
The downside to using a fixed pitch prop is that, of necessity, it will be a compromise in most parts of the flight regime. Because the Bearhawk has such a wide speed envelope, regardless of how you have a fixed pitch prop pitched, it will be slightly wrong at least part of the time. For example, one Bearhawk with a fixed pitch prop had a great takeoff roll and climb, but required a nearly immediate throttle reduction at level-off to prevent exceeding maximum RPM limits. With a constant speed prop, the throttle can wide open, or anywhere else, delivering much faster cruise speeds when desired. Special pricing is available on most props for kit builders when the props are purchased through Bearhawk Aircraft.