By on February 16, 2011

The thing that got me hooked on LeMons racing was the mentality that makes a statement such as “Hey, I’d like to install a 540-cubic-inch, five-cylinder radial aircraft engine in the back of a Toyota MR2, then try to make it run all weekend in a grueling endurance race” seem totally sensible. The craziest most devoted racers find themselves locked into an arms race for the Unununium, and this is the result.

The engine, which once powered a 1942 PT-22 Recruit trainer aircraft, was rated at 160 horsepower. This one hasn’t run for 65 years, but Radial Madman-In-Chief Marc assures us that it’s in good shape and should fire right up. As for the $500 limit, I exercised my authority as Chief Justice of the LeMons Supreme Court to issue a decree stating that radial engines shall be exempt from budgetary limits. You want a Pratt & Whitney R-2800 making 2,500+ horses in your Hillman Imp, and you can convince us that your hoopty-ass installation will be safe? Fine!

It’s going to sit in the back of the car, directly above a Subaru transaxle with a custom adapter flange. A V-drive, reduction gear set, and a much more reliability-enhancing gear is involved; you can follow the whole saga on this 24 Hours of LeMons Forums thread. Will it work? The real question should be: Will it have license plates?

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30 Comments on “Ill-Advised Engine Swap of the Week: Aircraft Radial In Toyota MR2...”

  • avatar

    When I saw that photo, it immediately reminded me of a pen-and-ink cartoon in Hot Rod Magazine about 1974, of a massive Cox .049 engine sitting in a rail, being fueled nitro by some slob with a cigarette in his mouth! Absolutely hilarious! I’m not familiar with a 5 cylinder aircraft engine, just 7 and 9 cyls. At least it wasn’t a Rhone rotary from WW1! That would have been interesting, to say the least. One note: Wasn’t the Tucker originally powered by a helicopter (radial) engine? Finally, how did the car pictured run?

  • avatar
    N Number

    I really can’t imagine this working out so well. In the aviation world, sometimes people put automotive engines in aircraft and these applications generally do not seem to be reliable.  An air-cooled complex and temperamental engine in the rear of the car is just asking to overheat or fail.  It develops peak horsepower at much lower rpm than automotive engines, so I’d be curious to see how well it puts the power to the wheels.

  • avatar

    This is such an awesomely deranged idea, the question “will it work?” kind of misses the point.

  • avatar
    bumpy ii

    This is the second-nuttiest SW20 engine swap I’ve seen.

  • avatar

    That is AWESOME.  For some reason, I was just thinking yesterday “I wonder if there’s ever been a radial engined car?”  I was thinking laying flat though.

    They should put a low-pitch propeller on it to keep things cool.

    That’s hilarious you’re exempting radials.  You should just have a law that if something is a REALLY stupid idea, it shall be exempt regardless of expense :) 

    If someone really wants to be the unununium grand champion, they’d be rocking a steam engine or any other kind of wood-fueled car.  Hey- great idea…I’d love to see a wood-bodied car that burns parts of it’s own body for fuel!

    • 0 avatar
      SVX pearlie

      Maybe someone can mount a jet engine in a station wagon??? Thrust powered!

    • 0 avatar

      We’ve had requests from teams who want to do steam engines, but the idea of a boiler explosion on the track has been pretty daunting.
      No jet engine attempts yet, though a couple teams are pursuing turbines.

    • 0 avatar

      …a couple teams are pursuing turbines.

      It won’t be a real turbine race competitor unless it’s accompanied by breathless magazine articles which proclaim that the “turbine era is finally here”, and fails 3 laps from the finish with a broken gasket / washer / screw / window defroster etc.

    • 0 avatar

      This is not the first radial-engined car. At the very least, there’s this little number
      I think it was featured on Jalopnik a few years back.

    • 0 avatar

      Radial engines in cars go back at least as far as the 1904 Adams-Farwell, which featured a fixed vertical crank and horizontally revolving engine.

  • avatar

    Reminds me of a Bill Cosby routine hehehe

  • avatar
    M 1

    MM, I’m the guy who wanted to run a ’51 De Soto on an outboard engine. We actually had some pretty sweet plans about how to make it all work too, but the whole thing fell apart when it became apparent that more of my team wanted to play than pay.
    At one point we had even sourced and considered using a somewhat rare Yanmar diesel outboard.
    The radial project, however, could very well trump our plan for awesomely bad ideas.
    By the way, here is another “interesting” use of a radial engine:

  • avatar

    I forsee cooling problems.

  • avatar

    Yup, the Tucker used a Franklin horizontally-opposed aircooled six aircraft engine.

    As for unusual engine installations, a few years ago there was a DeLorean (painted black) for sale in Florida for 25K. It had a Mazda 20B twin-turbo 3-rotor rotary, and an instrument panel that was from an early-’90s Honda Prelude. The youtube vid proved that this was a most excellent combination. The car was insanely fast.

  • avatar
    Robert Schwartz

    IIRC, in the 1950’s there were a lot of war surplus aircraft engines of the Rolls Royce Merlin type around. Liquid cooled, 27 liter, 1000+ hp. Dropped into a minimal frame with a little body work they made outrageous dragsters. Then a guy from Akron — Art Arfons decided to go whole hog and use a jet engine.

  • avatar

    Henry Ford experimented with radial engines in cars and I can’t remember the make but there was an early horseless carriage era car that had a radial engine whose cylinders and crankcase revolved around the fixed crankshaft, driving the car with a ring gear.
    Ah, found it! It was a Balzer (whose engines apparently ended up being used by S.P. Langley, the aviation pioneer for whom Langley Field is named)

  • avatar

    Radical Radial FTW! Here are my street finds for the week. 

  • avatar

    Normally I wouldn’t say anything but if you’re an owner of a mid-1960s and up Rolls-Royce then I am sure somebody has spoken of the Merlin V12 from WWII being able to actually fit in many of the engine bays (with minor modification).  Most of the time though they preferred to use the marine version which had a slightly smaller displacement that allowed it to be shoe-horned in.
    The disturbingly large 6.75L isn’t really derived from the Merlin anymore but the older engine bays are huge and had plenty of room to house the monster V-12 motors.  The increased weight & loss of a trunk to a fuel tank made up for the fact that a Rolls was able to blister time records and if I remember correctly would have been straight-line faster than most modern cars still…

    • 0 avatar

      I have to wonder what fraction of those attempts ended up top down.

      A common mode of exit for modern day P51 Mustang drivers remains the low speed torque roll induced by suddenly increasing the throttle to go around at the end of an aborted landing approach.

  • avatar

    Big cylinder aircraft engines are meant to cruise at a constant speed, usually producing 70% TO power or less, so this thing is meant to be set at about 110HP and left there.

    Big air cooled engines also do not like to have the power changed suddenly.  Quick power settings changes can cause thermal shock to big air cooled cylinders.

    Redline on this engine is 1850 RPM, why is a reduction gear being installed?  So a maximum of what, 925 RPM(??) is going into the transaxle?  BTW, Useable torque is probably from (let’s be generous) 1000 RPM to redline.  How many speeds will the transmission have to use this extremely wide power band?

    Engines of this vintage were meant to have a top oil for the valves.  One solution is to mix about 25% 100LL with 75% auto fuel so there is some TEL for the valves.  I’m sure the competitors will love breathing lead laced fumes.

    Radials are normally dry sump, so it will need an oil tank to hold, oh, three or four gallons of probably 100W aviation oil.  100W is about as thick as 50 weight auto oil, so perhaps straight 50 weight can be substituted.  Radials are known as oil burners, but since this engine is “in good shape” maybe it will only burn five gallons or so in a 24h race, assuming it doesn’t throw a piston through the head of a cylinder from excessive engine RPMs on the first lap.

    This could be interesting.  Is anyone making a video?  If it lasts half of a 24h race it should win a Unununium Medal.

    • 0 avatar

      Hi, this is Marc, the guy building this thing. there’s a few things i want to address about what you said:
      1) the refusal to change delivered power is due to the long intake tract and the archaic updraft carburetor. I’ll be using 5 carbs, one at each intake port to aleviate this (harley flat-head carbs)

      2) yes, the redline is 1850. we may push it a tiny bit past that, but not much. the gear reduction you mentioned is not quite that it’s actually a gear increase. about 3:1 to make the input shaft on the transmission spin up to 5500-6000 rpms about what the stock engine this transmission was designed for.

      3) thankfully, the leaded fuel is un-necessary. this engine has hardened valve seats. the only reason it calls for leaded fuel is because that’s what they had back then. we’ll be running on unleaded 93 octane or E-85 if we need the ethanol to help keep things cool.
      4) yes, we’ll have about a 5 gallon tank of oil on board. the plan is to run a 70W oil designed for harleys. it’s made to try and not sneak past the rings.
      5) yes, we will burn oil. there’s nothing much that can be done about that. the motor is quoted for 1.5gal/hr as “normal” i have no idea what the freshly rebuilt burn rate will be. it could be a quart/hr or it could be 1.5gal/hr.

    • 0 avatar


      It’s scary; after reading your post this engine swap is beginning to almost make sense to me.  Almost.

    • 0 avatar

      honestly the only significant risk at this point is cooling. i’m looking into semi sized cooling fans to move a bunch of air across the motor.
      the motor is in amazing shape. i had to make a few parts, but overall i lucked out and found a motor that had not been run to very long after it had been rebuilt. all the bearings were still in spec and very close to the new side of the specification. overall pretty amazing considering how cheap it was and that it was sitting in the corner of a barn. the rebuild date inscribed on the cylinders say 1944 and the lack of wear tells me it hasn’t been started in at least 65 years.
      the other big risk is the drive assembly between the motor and transmission. it’s a bit of a long shot and i have no idea how long it will last, but i suspect it should last long enough to impress most people :)

    • 0 avatar

      The trick to keeping the temperature down is fin area and this engine doesn’t have it.
      An out-of-the-box idea would be to take pieces of wire, wrap them around each cylinder, and then string them over to the adjacent cylinder like a big spider web.  Use wire of the same diameter as the cooling fin grooves so they fit in snugly.  Use copper for its good thermal conductivity.  It will look strange but it will have tremendous fin area.
      (Or you could just mount an oil cooler in the nose of the car, but that’s less fun!)

    • 0 avatar

      the cooling is definitely a huge concern. you’re quite correct that this motor has very short cooling fins.

      The upside is the motor is rated to 550*F head temperature. we’ll probably be using most of this. we’ll definitely have a huge oil cooler. the manual claims it does not want incoming oil to be cooler than 160*F. we’ll use that as our target temperature.

      the plan is as follows, incrementing until we no longer have a cooling issue.

      1) run on gasoline, use a radiator fan from a semi to move LOTS of air across the motor.
      2) switch to E85, fatten up the mixture for the cooling properties
      3) add a 10gal water tank and serious water injection

      • 0 avatar

        Just found the Kinner Radial as used in Toyota.
        Are you still using it?
        My Google search took me to you as I’m looking for the same engine for my Vintage Airplane.
        Know of anymore available.

  • avatar

    R-2800’s are for nancy boys and Pirus drivers. Real men re-engine VW Type 2’s with R-4360’s, or Beetle / Dune buggy conversions with Dirty-Three fifties.

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