An Internet drama in a teapot.


A little internet drama is a guilty pleasure of many aircraft builders. Submitted for your approval, a little drama that ran this week; It has a cast, a plot and a twist. Fun, but in the end it is only drama, and like a dozen other dramas before, it entertains, but doesn’t advance your plane toward flying.



Mark from Falcon Heads, Roy from Roy’s Garage, and 601XL builder/pilot Ron Lendon.



At the end of last year, I privately told Mark and Roy that I was no longer going to have them at Corvair Colleges nor in my booth at Oshkosh. After nearly 10 years of being their single most vocal supporter, I was tired of Mark not making heads and Roy telling people his work was “Technically Correct” with the implication that people choosing other suppliers were making a mistake. To retain some portion of builders, they decided Mark would come up with a special set of magic head mods for $500, and Roy would run people’s engines on his dyno with promises of further power increases. To sell this to people, they enlisted Ron Lendon to put it on his plane, and then tell people what an improvement it was. The broke the ‘story’ on the “Corvaircraft” discussion group, a venue where I am not allowed to participate.


It all sounded pretty good to people who like a good drama/conspiracy theory. Mark and Roy had “discovered” the dirty secret of Corvairs: The way we tell people to build them (Just as Mark and Roy have done for years) is terribly down on power. They claimed to have raised Ron’s power output by something like 24%. Ron followed up with a detailed flight report that showed his plane to now run 116-117 mph, a large improvement. Roy then comes in with some graphs showing Ron’s plane now makes 100 HP.


Sounds great, except:


Several well known and trusted 601XL pilots with 2700 cc Corvairs chime in to say that their planes are that fast already. Lynn Dingfelder and Phil Maxson, who have both been flying for years, point out that their planes do 115 mph, and Ken Pavlou’s will break 120, in the same configuration as Ron Lendon’s in spite of Ron’s engine being a 2,850 cc. The logical observation is that these unmodified airplanes have the same output as Ron’s now does, which Roy’s dyno said to make 100HP. Most people concluded that the test validated my long standing power output claims, because there is little variation in 601XL airframes, so the same speed  = the same power.




Points to understand:


Roy claimed to have previously tested a 2700 cc engine and the output was only 82-83HP. His contention was that all 2700s built to my suggestions had that power output. Clearly that wasn’t so, based on the other pilots reports compared to Ron’s ‘modified’ 2850.

I have little doubt that Ron’s plane had an improvement. He had been plagued by engine problems in his first years of operation, mostly caused by his adamant use of a obscure carb of a 65HP engine. In spite of working for GM for decades and having significant flying time, Ron  missed that his engine was running lean enough to damage itself bad enough to need a rebuild. His plane was never a particularly good performer by 601 standards. He got another Carb, much closer to correct, but still didn’t recognize it was running lean.


There was no ‘before’ run made on Ron’s engine, just an after. Although he mentioned that his plane now has flat top pistons, he didn’t mention that the heads were changes from 95 to 110 high compression ones,  the valve size increased, and again the carb was made richer. because it was never tested, there is no before and after, but judging from performance, his plane does run much better, but evidently not significantly better than other 2700cc 601XL’s. Changing the compression from 8;1 to 9.5:1 and making the carb a lot richer could account for the improvement alone. Perhaps the other ‘modifications’ have negligible or negative effect.

A great claim was made that Roy’s dyno was scientific because it used a data program called “Labview”. A guy who got it from his work traded it to Roy for a discount. Same guy claimed “This is basically the same software & hardware that is used on a $50-$100K dyno.” I tend to disagree because you can go on National Instruments website and see they sell the Labview dyno soft ware brand new for $1,290. I don’t think having  that software makes Roy’s dyno the equal tool as a $100,000 dyno.


No mention was made of correcting the dyno runs to standard atmosphere. Without this, there is no comparisons between engines, even ones run a few hours apart, far less weeks or months apart.






Above, Roy and I running an engine I built in 2014 on his dyno. Several people chimed in on Corvaircraft to praise Roy for his testing, even though they have no experience with dynos. Does this look like a $100,000 piece of equipment? On the day in the photo we could not get a test more than a few seconds long, and Roy had to manually manipulate the controls, there was no real data from this. I am sure it is better now, but this isn’t the “technically Correct” infallible tool that some people suspect.  If you would like to read a dozen stories of practical testing spanning 10 years, look here: Testing and Data Collection reference page



Above, a 2008 dyno calibration run in my yard in Florida. Notice Kevin and I are wearing jackets. We’re waiting just before sunset for a rare weather phenomena to occur: a perfect standard day of 59F 50% relative humidity and a pressure of 29.92. Any time you read a dyno report and it says “corrected horsepower,” they’re making a calculation, sometimes accurate and sometimes not, to adjust for their test conditions not being at standard atmosphere. Because we live in Florida near sea level, there have actually been three occasions the past years when these conditions were met during daylight hours on testing days.

Our dyno relied on the super accurate optical Prop Tach for the rpm measurement and it will only reliably pick this up in daylight. A few minutes after the photo above was taken, we made a dyno run which required no correction. By testing the same engine later in the week, we reconfirmed our correction factors for this particular dynomometer and we retained accurate measurements all year round. If you want to read the whole story, it is here: Dyno testing Corvairs, 2008 Any dyno run that doesn’t reference a correction to the ‘ICAO Standard Atmosphere’ has no meaning, and there is a significant difference between  the reliability of a calculated correction and a measured one, as we are doing above. People get excited hearing about ‘software packages’ but in reality the value of the tests relies on basic things like atmospheric corrections. 



Above, Ron Lendon, running his engine on my stand at Corvair College #17, having a good moment. Yesterday he said this on Corvaircraft: ” I even heard WW say to Dan W. that he would fly the engine I just built at CC17 to the Bahamas. But I don’t here him saying that now, no he is heaping his opinion on people he called friends because they are behaving as he did several years ago. “  A big part of why Ron’s engine ran great on my stand is that my stand has the recommended carb, a MA-3SPA. He promptly went home and bolted the incorrect carb on his plane, because it was cheap, starting a long series of issues. Oddly, the people Ron is championing today, Ron and Mark, supplied him with parts and service that he was previously angry about. As for his evaluation of the behavior of ‘friends’, perhaps he can review the definition of “ingrate.”



As for Mark or Roy being able to claim ignorance of the output of engines they happily built and sold to people, I submit the photo above: Marks EFI 2,700cc Corvair in 2007, on my dyno, right in front of mark’s shop in WI. He certainly didn’t think this motor, nor a carbureted one was 82hp that day. You can also see that Mark was present in the calibration story above. Roy had also flown as a passenger in Lynn Dingfelder’s 601XL and saw what a good running plane, with a stock 2700cc ww engine could do. Before making his claims this week he understood that his ‘modified’ engine in Ron’s plane was no more powerful than Lynns.

 My testing was absolutely satisfactory for Mark and Roy to sell heads and engines to people for years, but somehow they have suddenly ‘discovered’ that none of these engines worked, coinciding with them becoming unwelcome at events I am hosting. Think it over.




That concludes todays entertainment programing. I am headed back out to the shop to prep for the next Corvair College, I suggest builders intrested in progress do the same.


About William Wynne
I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at and in more than 50 magazine articles.

7 Responses to An Internet drama in a teapot.

  1. Vern Lehman says:

    WIlliam. You mentioned that larger valves were used in the “magic mystery” heads. I presume this means 140 Intake valves were machined to fit the 110hp heads? As you well know this is no simple task to be done correctly and even if so the 140 suffers from a lack of torque at lower RPM (which is why my 140 Automatic, one of 1965 Monzas, which dropped two seats now is much better with a fresh 110 mated to the 140 PG and differential). If this was the modification attempted it is a waste of effort and money. This alone would cause LESS torque at the typical operation of flight engines, the improvement is hardly worth the effort even in performance Corvair cars. Keep up the good work. Vern Lehman.

    • Vern,
      It was actually slightly larger valves, not 140’s Our 601XL has a 3100 in it with 140 heads during the second phase of its operations. You are correct, it was down on torque until it was above 2900 rpm, to compensate it had very high compression. It was a good demo motor, Andy Elliott later flew the same engine several hundred hours in his 601XL with the compression reduced to 10:1. Worked, but not a regular engine, and it would not have worked nearly was well on an engine with less displacement.-ww.

  2. Amos Vinyard says:

    “The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny – it is the light that guides your way.”

    ― Heraclitus

    • Jared Brown says:

      I teach high school biology and environmental science and just now I have decided to scrap half my lesson and teach those five sentences. I’m dealing with 14 and 15 year olds so this will take a while, but if only a few of them get it I think it will be worth my time.

  3. I’m sure it’s far easier for me to say, but your track record proves your character and integrity. I say waste no more time and breath on critics, ingrates, ‘friends’ that aren’t, etc. Simply major on the Truth, recommend the good guys like Dan W, do what you do best, enjoy love and life – it’s too short to waste on the flushable. Fair skies.

  4. Dan Branstrom says:

    When I studied economics, there was a Latin phrase used, “ceteris paribus.” It means, “with other things the same” or “other things being equal or held constant”. To isolate the effect of one variable in an experiment, other factors need to be held constant. That gives a true measure of the effects of one change.

    To change a whole series of factors at the same time makes it much more difficult to determine the effect of one change. Also, in the first place, not having followed the recommended configuration that develops 100 hp also makes his results problematic.

  5. As a degreed Aeronautical Engineer with past experience in Flight Test for aircraft certification along with a bit of work on Navy Cruise Missiles I will make a simple comment. The data is apparently claimed to be superior because it was collected with a COTS product called LabView. I have never worked with that product but understand its purpose to be data collection and presentation, maybe even some data reduction as well. As such it is a tool and does not make the experiment better or worse, it just provides a lot of easily accessable information. Now with a properly conceived experiment that is properly executed and properly instrumented the data should be useful for analysis by an experienced engineer. On the flip side if any of those criteria fail than the data is essentially meaningless even when filtered through the educated judgement of an expert in the subject. So the bottom line is that using LabView to establish the accuracy of the test is really just so much smoke intended to impress the unknowing. “Garbage In, Garbage Out” is a common expression in software engineering. I do not know the quality of the testing that was performed but given my own experiences with the people involved my gut feel is to accept what WW has concluded.

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