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Piper PA-18 Super Cub IO-390 STC

210 HP Conversion - The Ultimate Super Cub Upgrade. We call it: The King Cub.

King Cub IO-390 Conversion Kit

The King Cub IO-390 Conversion Kit is everything you need to convert any cub into a King Cub. The upgrade is STC approved and increases performance, with minimal weight sacrifice and better fuel economy. With the King Cub upgrade, your Cub will experience shorter takeoff, faster cruise speed, better float performance and much smoother operation.

Comparison: Lycoming IO-390 vs. O-360

  • Much smoother operation - Feels like a turbine with the roller tappets and cam and counterweighted crankshaft.

  • Fast, powerful, with very little weight sacrifice over 180 hp engine - Compare engine weights:

    • Lyc. IO-390, 210 hp...308 lbs.

    • Lyc. O-360 "A" series, 180 hp...285 - 301 lbs. *

    • Lyc. O-360 "C" series, 180 hp...285 - 290 lbs

  • Fuel Injection allows for better fuel economy than 180 hp engines

  • Fuel burn almost identical to O-360, 180 hp engines @ the same hp output.

    • 70% HP​

      • IO-390: 146HP...10.4 GPH​

      • O-360: 126HP...8.8 GPH

    • 100% HP

      • IO-390: 210HP...16.9GPH​

      • O-360: 180HP...14.9GPH

  • Faster cruise speed - 115 mph TAS @ 25 square

  • Amazingly shorter takeoff distance

    • Takeoff distance, ground roll...75 ft.

    • Takeoff distance, 50 ft. obstacle...225 ft.

  • Much better float performance - Climbs at 1000 fpm (tested on Wipline 2100 amphib floats)

  • Increase aircraft's value - A factory new or rebuilt engine combined with a horsepower increase offers a significant increase in the aircraft's value

The King Cub IO-390 Conversion kit contains:

  • Lycoming IO-390-A1B6 engine

  • MT MTV-15-B/210-58 Constant speed, composite propeller, 82.7" diameter

    • NEW! STC Approved MT MTV-15-B-C-R(M)/CR210-58 Reverse prop now an option

  • MT Prop Governor, P-860-3

  • MT Spinner, P-277-6

  • New dynafocal engine mount - w/ new Lord mount bushings

  • New Weldon electric fuel boost pump

  • All new engine baffles to fit the IO-390 / Piper combination

  • Two new oil coolers

  • New lightweight alternator

  • New lightweight starter

  • New SlickStart Magneto Booster system (req. as the IO-390 does not come w/ impulse couplers)

  • All new exhaust system

  • New nose bowl and complete cowling assembly

  • New Alternate Air Box

  • New Brackett Air Filter assembly and element

  • All new control cables and brackets (Throttle, Mixture, Prop Governor, Alternate Air)

  • All new fuel lines, hoses and hardware for fuel system assembly

  • All new oil lines, hoses and hardware for oil cooler plumbing and ducting

  • New placard set

  • Other miscellaneous hardware necessary for the conversion

  • All STC paperwork


Required items: To see a list of items that are required in order to install the conversion click here (PDF).

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This kit may be performed on brand new aircraft bilds, FWF installs on an existing aircraft, or purchase our kit and have your A&P install it for you. 

King Cub Wins Gold At Takeoff Competition

We placed first with the King Cub kit during the 2010 Greenville, ME International Seaplane Fly-In.

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