25 years after warning people, cast pistons still show up in planes.


More than 25 years ago, long before the internet, I wrote my first Corvair manual, and printed it on a then modern dot matrix printer. In that manual, and in every one since, I have told builders not to use cast pistons in aircraft motors. I have never built a single flight engine using them, and this is not a new position. Yet, after all these years, people still put them in engines, and if they later resell that engine, it is frequently said to be ” Built to Wynne’s Manual”, a statement we would generously call “misleading”, the polite word for “dangerous lie.”


The two reasons people put cast pistons in motors are they are cheap, and they are advised to do so by a “Local Expert”. If you want to read a direct story of this, follow this link:“Local Expert” convinces builder to use cast pistons. When you are done, please get a look at this story, and the links in it before buying anything: Junk you should not buy..


Many people believe in “Let the Buyer beware” and I sort of do, but not in aviation where the penalties are pretty stiff. Truth be told, I have another angle also: When junk like cast pistons fails in a Corvair, none of the people who look at it say “That was not compliant with how William teaches people to build engines”  In almost every case, nearly every witness will only learn Corvairs=Bad. Most people are not very sophisticated in how they develop opinions these days, and they bring that to aviation, complete with a ‘facts don’t matter’ attitude.


Many people know that a very large effort was put out by a law firm to blame me for a non-fatal accident several years ago. This is an extreme example of how people who don’t want to listen to my experience will not take personal responsibility for that decision. The facts: I didn’t sell the person a single part. I sent him 11 emails saying his plane was un-airworthy, including one the day before his 45 second flight. He refused, in email, to buy a timing light saying the previous owner must have set the timing. He was a 60 hour powered Parachute pilot with no transition training. He brought a passenger on the first flight. His Dynon recorded the CHT at 628F in 45 seconds into the take off.  He used low grade car gas for the flight and failed to conduct a two minute test.  All of this made no difference, they still wanted to get it into Federal Court in Arkansas. So If I sound heavy handed on this and not very libertarian, it is because after something goes wrong, the guy who made the choice almost never stands up and publicly says “This was my fault.”



Above, these came out of a motor which a guy was actually building to fly. The motor was based on a Short stroke early Corvair, with a weak early crank, no 5th bearing, and plenty of other things I have told people to never do. If you look above, an irony: they guy used billet connecting rods with Chinese cast pistons. If you look at the underside of the piston there is a mark that is a G outside and N. It is a Chinese brand.  This engine was sold to a builder, who fortunately treated it as a core motor. It came to Corvair College #42 as parts. But someone who owned a manual of mine actually put this together to fly. If it was flown, it would have almost certainly broken, and caused a crash. How would you like it if a wealthy law firm claimed this was your fault? Welcome to our legal system. As I have said many times, I am a devout believer in the ideals of our nation, but the execution of those ideals can fall pretty short at times.




3 Replies to “25 years after warning people, cast pistons still show up in planes.”

  1. I guess the old saying “You Can Lead A Horse To Water But You Can’t Make Him Drink” still rings true. These stories never fail to surprise me as to how flat out stupid some people involved in aviation can be. One note, it would have been a good comparison to see what a truly airworthy forged piston looks like as a comparison and maybe a short primer on how they can be distinguished for those not up to speed on materials science. It is a subject covered many times from various angles but it might be nice for others to know how to spot that Chinese crap when they see it. My own engine has good forged pistons in it but regrettably it also has Chinese rocker arms and when I have the time (before it even gets mounted to the airframe) to open up the rocker covers and replace them with the proper parts, those old ones will get a good whack with a sledge hammer so that they have no hope of getting used again.

  2. The engine being discussed here was mine. I am a new arrival to the home building world so I proceed with caution because I know what I don’t know. Which is everything! That said I decided to put some context out on this story from the viewpoint of the consumer. This is because I keep seeing Corvair engines for sale in online postings that look very similar to what this engine looked like when I wheeled it into my garage. And these engines are almost always described as “WW approved” in some way. I bought this engine as a core from a gentleman who bought it at an estate sale several years ago. He made absolutely no promises to me about what condition it was in. He just told me it should do a good job of getting me started in building my engine, and he was right. He even delivered it to my house from two states away. I still owe him for that one. Thanks John!

    He never made any statements about it being anything other than a core that was ready to be torn down. But it sure looked like it was a converted and functional engine. I was worried when it came off the truck. This looked like a converted engine, not a core, and I only had core money to spend, not engine money. It didn’t look good for getting a deal done. John being much smarter than me, and extremely honest to boot, knew that it was going to be a voyage of discovery exploring what was inside. Proof of that was that he was willing to sell it to me for the price of a core, not at the price that it’s external appearance implied, which would have been a much higher number. Somone had clearly spent some money on this engine so I was confident the guts would be at least workable, maybe even usable as is? I figured at worst I’ll have a solid core for parts and some external components as well. Either way I was just happy to have a core and get started on my engine. We made the deal and went out to have dinner and some excellent conversation. I made a new friend, a great deal already.

    That weekend I started tearing it down and was shocked at what I found. Whoever put this engine together clearly had a WW manual and bought some of his components, but skipped steps 1 through about 120. Wrong case, wrong crank, wrong heads, wrong pistons, wrong cylinders, wrong rockers, the list goes on forever. The best irony? They drilled a hole through a brand new top cover to install a fitting for what I guess was supposed to be a return oil line. What a waste. Even so there were plenty of parts on it for me to salvage and many will go on my engine, but much of what had been put in or on it was substandard garbage, or attached to said garbage, thus making it all garbage. I have since gotten another core and am off and running. But with a solid lesson under my belt. Here’s the lesson: If you didn’t build it, you have absolutely no idea what’s in there. None. You are buying a mystery that won’t be solved until you tear it down and inspect every part. In my case, even after tearing it down and studying the manual and videos I needed a great deal of William’s help to sort the sheep from the goats. And many of the parts I was really wanting to use, and thus save some serious money, went into the dumpster instead. If I’d had a beer I would have been crying in it. William was unmoved by my growing distress while he went through every part telling me what was good, and more importantly what was bad, and why. So I wept, while chucking the bad stuff into the dumpster. Good thing the dumpster was in back, where I could preserve my dignity and mourn in private.

    So this was my experience buying an engine that looked solid but turned out to be completely devoid of the correct internal components. Everything inside that case was wrong. Every. Single. Thing. I am not complaining, far from it. I got a pile of good components off that engine, and for the price of a core it was a very fair deal, very. But if I’d bought that engine thinking all it needed was some minor updating and an overhaul, and paid many thousands for it? A very different story that would have been. And this was my experience with a seller who did not attempt in any way to misrepresent what I was buying. In fact he went to the opposite extreme. Imagine what you could wind up buying from someone not as honest.

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