Air Repair Jacobs Engine Conversion for the Stearman

//Air Repair Jacobs Engine Conversion for the Stearman

Air Repair Jacobs Engine Conversion for the Stearman

Two years ago Pete Jones of Air Repair, Inc., in Cleveland, Mississippi, was able to make an acquisition that would reinvigorate the Stearman market.  In his mind, purchasing the Jacobs Aircraft Company, would give the Stearman a much-needed shot in the arm.  Although this is not a new concept, Air Repair, Inc. has developed the installation to make it more readily convertible, by following the straightest line possible between the W670 Continental and the R755 Jacobs. 

Two years after the purchase, Air Repair, Inc. received an FAA S.T.C. #SA02322AT for the installation of the 275HP Jacobs R755-B2M engine on the model 75 series Stearman aircraft.  There are no major modifications to the oil system, induction system, fuel system or carb/heat system.  The heart of the conversion is an aluminum adapter plate used to mate the Jacobs mount pattern to the Continental engine mount.  The plate was subjected to an FAA approved stress and load test.  The plate was taken to ultimate “G” loading with no deformation. 

The next key component was the exhaust & carb/heat system.  While many people have installed the R755 engine most of the installations have made use of surplus Cessna T-50 Bobcat exhaust and intake  components.  In an effort to return to the Continental look and simplify the conversion, Air Repair, Inc. contracted with Aircraft Exhaust Systems to build an all-new exhaust collector.  The collector fits in the Continental exhaust well or “dishpan” and by moving the exhaust shroud around slightly the same shroud and shroud look are retained.  Air Repair, Inc. designed and had fabricated aluminum intake horns that connect the NAR7 carburetor to the original induction system.  Brackett foam element air filters are standard equipment. 

Flight tests conducted by Pete Jones included tests for carb/heat, oil temperature, cylinder head temperature and handling characteristics.  The tests revealed that the 90ºF heat rise for carb/heat could not be obtained.  Further investigation revealed that by extending the upper air tube 3”, that the carb heat differential requirements could be easily be met with the added benefit of cooler induction air. 

The oil system and fuel system required no changes.  The Airwolf oil filter is standard equipment.  Bendix 397 series starter and Jasco alternator are also standard and are the same units used on the Continental installation. 

The throttle, mixture and carb/heat are controlled through the original Bellcrank and rod system.  An Arens type flex control cable controls the prop governor.  The only added instrument is a manifold pressure gauge.  The engine uses the dual mag set-up and uses existing P-lead and switches.  The propeller of choice is the Hamilton Standard 2B20-15 constant speed propeller. 

FAA test pilot Doug Andrews performed the FAA flight tests

and most forward C.G. take-off performance was approximately 350’ on an 85ºF day with 1000FPM climb-out at 75MPH.  All cooling tests were well within limits and the aircraft handled well in all stall configurations.  Cruise speed was at 2000RPM and 22” is approximately 110MPH at 13GPH.

 The Jacobs engine has been hung with the nickname, “Shakey Jake”, but other than the two words rhyming, Pete can see no basis for the name.  After trying to work with Teledyne Continental since 1987 on pistons, with no luck, the Jacobs engine was appealing, due to the availability of technical data.  When the company came available Pete took advantage of the opportunity and became the Jacobs type certificate holder.  Air Repair, Inc. now has all of the engineering and technical data along with a very large and complete spare parts inventory.  Air Repair, Inc. currently holds FAA Parts Manufacture Approval to produce link rods, pistons, valve guides, valve seats and many other items for the R755.  The R755 is a proven power plant on the Cessna 195.  The R755-B2M which is rated at 275HP, but will actually dyno test at 294HP, compared to the 300HP Lycoming, which is slightly overrated, the Jacobs would probably test out the same if not slightly higher.  All of these facts coupled together make the Jacobs engine the most viable small radial engine for the next 50 years.

 The 275hp Jacobs is available on new airplanes from Air Repair, Inc. or can be furnished as a conversion kit or converted by Air Repair, Inc.  Air Repair’s new airplane price is $189,000.00.  Your aircraft can be flown to Cleveland, Mississippi and converted in two working days for a cost of $25,500.00 exchange.

 The first new Air Repair, Inc. Stearman restoration, #129, was delivered on May 15, 2001 to Jay Gordon, Jr. of Louisville, Kentucky.  The next two Jacobs powered units #130 and #131 are scheduled for delivery in late June 2001.  Air Repair, Inc. plans to demonstrate the conversion at the National Stearman Fly-in by converting an airplane at the fly-in.  Currently, Air Repair, Inc. has an FAA project in the works to complete certification on Bendix fuel injection and electronic ignition.  Completion is expected in mid 2002.  Horsepower output is calculated to be between 313hp and 325hp with better cooling and fuel efficiency.

 For “half time entertainment” at this year’s Stearman Fly-in in Galesburg, Illinois, Air Repair, Inc. will convert a Continental powered Stearman to the Jacobs R755.  As an incentive to some lucky person we will be offering the conversion at a discounted price to the candidate selected. Contact Pete Jones to find out more about this great offer.

 If your Continental engine is near the end of the line or you need that extra takeoff power, the 275hp Jacobs R755 could be the answer to your prayers. 

Rear View of engine showing installation of adaptor plate 

Right hand view showing original W670 air intake and carb heat


Left hand view showing W670 fuel & oil system and Airwolf filter


 Except for the 2B20 propeller, the engine installation is virtually identical to that of the W670


By |2016-11-13T09:33:58+00:00August 9th, 2001|Flying-Wire|Comments Off on Air Repair Jacobs Engine Conversion for the Stearman

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