“Local Expert” convinces builder to use cast pistons

Builders:

When we were at Oshkosh this year, a man walked into the booth on a slow afternoon. After 20 years of doing presentations at airshows, I can say that it is very hard to predict who the serious builders are when they walk in for a look, but I can always tell in 10 seconds who is there with an “issue.”  None of these people are actual builders, they are all “Local experts” who want to tell me that they know more about Corvair flight engines than I do. Mostly, they are harmless blowhards there to complain that none of our builders respect their “advice.” But the particular guy who walked into my booth was a dangerous idiot because he had actually convinced a Corvair builder at his local airport to use cast pistons in his engine, completely against advice I have been giving for 25 years. He came to the booth to gloat over his success. In reality he had just seriously endangered the builder, and every one of the man’s future passengers, all for the sake of his own ego.

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Above, BHP’s Corvair powered plane The Last Original. This plane has 800 hours on it today. It lives at Brodhead and belongs to our friend Bill Knight. Contrary to what some people think, this plane has forged pistons in it.

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The builder in question is a guy I have known for years; He is a very nice guy, his Pietenpol is almost done and it is outstanding in appearance. At any grass strip, this man and his plane  would inspire confidence to allow many people to let their child take a flight in his plane. Externally, this engine would even look like one “built to WW’s specs.” But with Chinese cast pistons in it, this plane contains a very dangerous hidden flaw with a very high probability of a disaster awaiting.

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Most planes that are the aviation equivalent of an IED look the part, and are presented by people who are easily recognizable as mentally ill. People understand to stay away. What makes the plane described to me at Oshkosh so dangerous is that the finish and demeanor of the builder will be very disarming. I don’t have to warn people about what to do if they meet a guy with a wild look, speaking about the afterlife and holding a grenade with no pin. This warning is about recognizing that sometimes the same grenade is wrapped in a very nice gift box, and the pleasant guy offering to let your kid look inside doesn’t himself understand the contents. All he knows is that his “local expert” (who will not be flying in the plane) assured him that he and his passengers were in no danger at all.

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The dangerous idiot local expert stood in my booth and offered these reasons why he told the Pietenpol builder not to use forged pistons: 1) the cast pistons were made in the U.S., and our forged ones were made in China, 2) Bernard Pietenpol’s own plane The Last Original has cast pistons, 3) The engine only makes 70 HP so it doesn’t need the extra $80 expense (per set) that forged pistons cost. Everything this man said is a vile lie, but dangerous idiots never restrict themselves to the truth nor reality when dispensing “advice.”

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Lets look at the lies one by one: 1) In reality, it is the “High Tech” cast pistons the idiot advocated putting in the engine that are made by the Chinese. Every forged piston we have ever sold was made in California, so the idiot had it 100% backwards. Every cast piston for the Corvair that I have seen for sale is a product of China. They may say “ISO-9001″ on the box, but that is just printed words from a culture of corruption.

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2) BHP’s own plane, The Last Original, does not have cast pistons in it. A number of years ago, Bill Knight, the owner, contacted us about upgrading the engine to my spec’s internally. The only visible external change is that the engine has our black prop hub, but internally, it is all modern stuff out of our Conversion Manual, including forged pistons. I have one of the original GM pistons in my shop, and it is in poor shape. Bill Knight made a very good call on standing the plane down until it was updated. The actual engine assembly on the update was done by Mark Petz, who was standing in the booth when the idiot was saying his lie. When I asked the idiot if he would like to personally meet the man who put the forged pistons in The Last Original, the idiot was dumbfounded.

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3) Everyone who came to our booth at Oshkosh this year saw both the display engine I built and Roy’s water brake dyno.  After Oshkosh, we went to Roy’s in Michigan for a day and did a complete break in run on the display engine before delivering it to a Canadian Zenith 650 builder. Because the engine was brand new, I didn’t lean on it very hard, but the engine pulled 76.5 HP at 2,675 rpm, which is below the static take off rpm of a Pietenpol. If the idiot was counting on a modern Corvair to only make 70 HP he is very wrong. I owned a dyno for years that we ran countless engines on in public, Roy has a better one, and Mark owns an even more sophisticated one. I am sure that the idiot based his guess on nothing, because that is what idiots do.

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Even if the engine was to produce only 70 HP, it should still have forged pistons. In reality, all the original GM pistons were cast, but they were vast better quality that the Chinese junk sold today. The GM pistons were all U.S. made and had a steel belt cast inside to control expansion and strengthen them. Because people flew them in the 1970s means nothing about Chinese parts today.

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The great danger in using cast pistons is that undoubtably the builder is going to use our CHT limits, ignition advance curves, carb jetting. cam, rpm, spark plug and prop recommendations, which are all based on the engine having forged pistons, a requirement I have held for 25 years. It is my prediction that the builder will blow a hole in one of his Chinese pistons in the first 25 hours of operation. When he does this, he may not get back to the airport, and he may wreck the plane and get hurt. Does anyone think that the idiot will then show up and build him a new plane and pay his medical bills? And then people will say, “See Corvair engines don’t work,” neatly ignoring that Continentals with the wrong pistons in them don’t work either.

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I have not included the name of the builder here, because I want people to focus on not listening to local idiots. I have said this countless times, and I have no idea why the builder couldn’t just say, “Sorry, no offense, but I am going to just follow WW’s recommendations.” After I publish this I am going to go on the Matronics Pietenpol list and state the builder’s name, and say that I do like the guy, but his engine is unairworthy.  I will do this in hopes that he will change them, but if he doesn’t, and his Chinese cast pistons fail, it will be public record that I warned him, and maybe the next guy will learn not to listen to idiots.

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Above, Tom Brown’s Pietenpol, flying since 1982. It has more than 1,500 hours on it. It is often said that this plane has cast pistons in it, but we are very good friends with Tom, and he has told me that he and his dad rebuilt the engine after briefly flying it in 1982. It may have forged pistons, but if it does have cast ones, they are U.S. made ones from GM, and they are vastly better quality than any cast piston from China. This plane does not use the full ignition advance, cam nor carb jetting we use today.

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It is not possible for me to express how much I detest people who will not fly in planes, but give advice to others contrary to what our testing has shown. Words like “Vermin” hardly cover it. I suggest that people read my story about how fools in aviation have an ironic way of hurting others and walking away without a scratch, at this link: Effective Risk Management – 2,903 words.

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The link contains the story of a great aviator, Phil Schact, a man hugely influential on Grace’s flying, who burned to death as the direct result of an idiot’s actions. In the year that followed that accident, I spent a number of long quiet nights sitting on the front porch thinking, and came to the conclusion that I will never be a good Christian, because I was not willing to even contemplate forgiving that idiot. I understand the power of forgiveness, in my life I have been both the recipient and the grantor, but we know the real measure is can you forgive the unforgivable? By this measure, I will always fail to forgive dangerous idiots in aviation. No matter how long I live, I will go to my grave with this black mark on my heart. -ww.

Pros and Cons of Roller Rockers

Builders:

In the discussion of rocker arms, the subject of roller rockers comes up occasionally as an alternative to the stock ball type. While they are made in America and very fine quality, there are actually some pros and cons to using them in a flight engine.

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First, a bit of history: Roller rockers were developed to replace ball types so V-8s could use 7,500 rpm and cams with .650″ lift. They were never designed with simplicity and longevity in mind. Back more than 12 years ago, there were several Corvair car parts outfits like SC performance and Clarks selling roller rockers, and most of the literature implied that they were developed by these companies. This all seemed reasonable in a black and white photo. However, the first time I saw an SC performance rocker in person, I saw it was orange in color. Because I spend my youth on NJ drag strips like Englishtown, Atco and McCarter highway, I instantly knew they were made by a company in the middle of America called Harland-Sharp. H-S didn’t have a website as late as 2003, but they directly sold to builders and they were a lot cheaper than SC Performance, which carefully trimmed the H-S name off the packaging before marking them up for resale.

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Part of the internet hype at the time was roller rockers lowering oil temps and boosting power in Corvair engines. Neither of these are vaguely true. I bought a set just to test, and when our 601XL flew in early 2004, I am pretty sure it was the first Corvair powered plane to fly with roller rockers. We flew it several hundred hours and checked the valve train intermittently. They worked, but just as I predicted, no change in power nor oil temp. Other builders followed this with even more hours, notably Mark Langford who eventually flew more than 1,000 hours on the same set without issue.

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When installing roller Rockers several other items must be changed. They need to be mounted on longer rocker studs, commonly sold by Clarks as #9295.  (The studs that Langford and I used were made by ARP in California, and the current Clarks item looks visibly different, but I don’t know their origin.) They must have deeper than stock valve covers, custom length pushrods and Poly-locks.

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Roller rockers have their own adjustment nuts called “poly-locks” It is basically a threaded tube with an Allen set screw up the middle that jams on the top of the stud. Most builders and car people don’t understand the two reasons for the existence of Ploy-locks are very rapid adjustment of the clearance on mechanical lifer cams on V-8s (This is not for maintenance, it is to alter the power delivery on the engine, often to suit traction conditions in drag racing. These went with the little T-handle hold downs bolts on valve covers) and second was to allow the use of a device called a ‘Stud Girdle’ that clamped the tops of all the Poly-locks rigidly together to prevent the from flexing when using combination of very high lift,  very high spring pressure and astronomical rpm limits, none of which is ever remotely seen in Corvair flight engines.

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PRO: Dan Weseman, Florida, 400 hrs on 3,100cc Cleanex , 125 hrs on 3,000 cc Panther.

Above, Dan Weseman and I stand in our front yard. This was the first run of the Panther’s engine.

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I spoke with Panther designer and builder Dan Weseman on the phone yesterday. When his Corvair was assembled we put it together with new rockers, which turned out to be Chinese ones. He is going to replace them before flying again. Dan said he is thinking about a set of H-S roller rockers. His engine was already built with longer studs, so all he needs are the rockers, a new set of pushrods, and perhaps doubling up valve cover gaskets. Dan was a hard core hot rodding guy before getting into planes, mostly working with small block Fords in Mustangs. He has had many sets of roller rockers and is pretty confident that he isn’t going to have a reliability issue. He points to our experience and that of Langford. It isn’t a guarantee, but he finds it it be a good indicator. He is well aware of the life-span limitations on roller rockers at very high loads, but judges that operating them on flight engines are well below this threshold.

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CON: Woody Harris, California, 440 hours on 2,850cc 601XL


Woody Harris, above left, and his friend Steve celebrate with cigars and Piper Heidsieck champagne after the first flight of his 601.

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I spoke with Woody today. He is the guy who just broke the exhaust rocker on 9 August. He is going to change all his all his rockers out before flying again. He took a moment to amend my notes saying he had 160 hours on his rockers; after that first guess, he checked his records and found out that he actually had 350 hours on the Chinese rockers. He strongly suspects that he got that far because before installing them he did a very careful job of meticulously de-burring all the surfaces in the ball area. I include this because if anyone suggests that the issue with Chinese rockers was improper installation, we can just put that to rest now. The issue with them is poor quality control in manufacturing, period.

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Woody is pretty sure that he is heading back to GM original rockers, not roller rockers. Woody functions as our ‘man on the west coast.’ Many builders have met him this was and have had a glimpse of his racing background. Lots of people have had something to do with ‘race cars.’ On the other hand Woody has run a Ford GT-40 to the lap record at Brands Hatch and was McLaren’s rep in North America. He also has a lot of experience with roller rockers, and he isn’t going to put them in his plane. He ran roller rockers in very demanding situations and thought they required constant attention. He concedes that our application, doesn’t stress them anywhere near that far, but his point is that the original GM rockers have a very long history of working, and he simply wants to move back and tap into that reliability. Nothing wrong with the ball design, it is just a question of who made the parts. To Woody, roller rockers are an answer to a question that our application is not asking. Today he is just looking through his collection of used GM original rockers from core engines to find 12 in good shape. We additional spoke about looking at several different brands of grooved balls to see if they are made differently, but I pointed our that I have been using the ones from Clarks with GM rockers on all of our engines in the last 12-14 years, without issue.

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“Tell me what to do.”:  Obviously I make recommendations about how to build Corvair engines, but I always first try to lay out the background information. I am here to share what we know, not simply tell people what to do, and I thought this was an ideal question to highlight this on.

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There will be plenty of people who chime in with no personal experience and tell others what to do about rockers. I try to be polite, but that kind of info doesn’t help anyone.  Second there are people who will point out one other person’s experience, like Mark Langford’s 1,000 hours on roller rockers. Information like that doesn’t help either, because in many cases the person bringing it up doesn’t know many of the important difference in assembly or operation that may be a factor. It is my business to understand these, and I politely point out that many comments chimed in often miss details or are off the issue and outside the cause-effect-solution chain. Last let me point out that even one guy point out what has worked for him for 1,000 hours is just a good data point. To have the complete picture, one must have the global view, and include all data points (with their details and conditions) including all the parts that never broke. I am in a good position to provide that perspective on Corvair engines.

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To me, the best solution for most builders is the path that Woody is taking, to go back to having GM original rockers on flight engines. These have a very long track record of working, they are very cheap, and they can be retrofitted in a few hours, end of story.  However, there are a number of builders like Dan who will consider roller rockers, and for those builders I wanted to provide the pros and cons here, to have them make a far more informed choice.  We have our own 3,000cc Corvair going together for our Wagabond, and I have both a set of Harland-Sharp rockers and plenty of GM ones. I would not be reluctant to fly it either way, but in the next weak or two I am going to give some consideration to which to do the final assembly with.

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Below, some notes and photos from the archives:

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 Below, a picture from the Summit Racing website. There are different sets for 140 hp heads and another for 110/95 hp heads. You can not mix them because the splay angle of the valves in the heads are different. The ball design of the original rockes negates this, because the axis is free to float on a ball rocker and it is rigidly set by the trunion angle on a roller rocker. Most sets sold to car people are the 140 hp sets, the difference is so fine that it can’t be seen holding it in your hand. Keep this in mind before buying a cheap used set off ebay.

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Harland Sharp SC110 – Harland Sharp Original Roller Rockers

Click here for more information about Harland Sharp SC110 - Harland Sharp Original Roller Rockers

Rocker Arms, Stud, Full Roller, 1.58 Ratio, Aluminum, Orange Anodized, Chevy, 2.7L, Set of 12

Part Number: CSP-SC110

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Above, a 2005 photo of an engine we built in our old Edgewater hangar, sitting on the old dynamometer, showing the roller rockers. We built about eight engines like this. All the pushrods we used came from the Smith Brothers on the west coast. Every engine with roller rockers requires non-stock length pushrods to have correct valve geometry. It is not tough to measure, but we met many builders who guessed wrong  on their first try. Old 3,100 engines all required custom length pushrods, and this was an Achilles heel of the engine for first time builders. We eliminated the custom length pushrod issue when we went to the 3,000 cc engines six years ago.

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Above, a 2003 photo of the 2,700 engine we assembled and flew in our 601XL. This was the first Corvair powered plane to fly roller rockers. The longer studs required by these rockers, and their poly-locks (the locking nut system for a roller rocker) dictate deeper valve covers than stock. Traditionally, car people used heavy cast aluminum valve covers. Above is my solution: I milled away the center flat portion of the valve cover, folded up two boxes which were 3/8″ deep, out of .020 steel. I welded these on in place of the removed flat spot. This was not a particularly easy weld bead.

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Here is the modified valve cover installed, above. Also visible in this shot is titanium-ceramic exhaust coated by the Moore brothers, a famous shop which does STC’d coating on aircraft parts. This design and method was superseded by all of our 304 stainless steel exhaust systems

 

Safety Alert: Chinese Rocker Arm Failures

DATE and REVISION: 10 August, 2014. Original Safety Alert.

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- 18 Aug.2014 – amended with ‘further reading’ with link to Roller rocker story.

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SUBJECT: Failure of Chinese made “New” rocker arms for Corvairs, marketed by several firms in the US, most commonly sold by Clark’s Corvairs as “new replacement rocker arms,” sold as set #C-8641.

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APPLICABILITY: Recommendation for all Corvair flight engines that have these installed.

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EXCLUSION: This does NOT apply to any Corvair flight engine using original GM US made rocker arms, just engines using the Chinese replacements. NOTE: We have never built any production FlyCorvair.com engine using these rocker arms. If you own an engine actually built by myself, this Safety Alert does not apply to it. This Safety Alert is issued for the benefit of builders who may have independently elected to purchase the Chinese rockers for their personal engines.

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COMMENTARY: Yesterday (9 August, 2014) in California, a Corvair powered aircraft experienced a severe loss of power following a failure of an exhaust rocker arm. The power loss was progressive over a few minutes. Excellent pilot judgment, to turn to the nearest airport at the first sign of an issue, paid off. The airplane landed on the runway back at the airport without damage.

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( When a four stroke engine has an intake rocker arm fail, the engine only looses power from that cylinder. Conversely, an exhaust rocker failure does not allow burning air/fuel to exit the combustion chamber, and when the intake valve opens it tends to “flash back” up the intake tract and rob power from the neighboring cylinders.  Intake rocker failure on a Corvair would be less than a 20% power loss, but an exhaust rocker failure could be up to a 50% power loss.)

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32 days earlier we had received a detailed report on the failure of a Chinese made Corvair rocker arm in Arizona, in the intake position on a 3,000cc Corvair.  This happened on a ground run up, not in the air.  Obviously as a ground issue, there was no damage to the airframe. It was of concern to the owner, but not the kind of stress as in the 9 August failure.  Although there had been a report of 1 other failure in the previous 5 years, that engine had many extenuating conditions such as a previous piston/valve collision. The 6 July 2014 failure was the first one that was on a “pure” engine. The parts were carefully inspected by a professional engineer, and the probable conclusion was that they were incorrectly made. The rockers had been purchased from Clark’s Corvairs, and they were contacted for a failure history in cars. They stated that they had seen a very low rate of returns in cars. (As a reminder, Clark’s does not sell these as “aircraft” parts, that is a builder choice.) I supplied a set of GM rockers to the flyer in Arizona and his aircraft was returned to flight with about 2 hours of work and less than $100 in parts.

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At Oshkosh I spoke with a number of builders of flying Corvair powered planes to asses how widespread the use of these Chinese rockers are. I had previously thought it was a small number, as I used none of them in our production engines, I have never sold nor promoted the Chinese part, and I have been long recognized as a tireless critic of Chinese manufactured parts. My estimate is now that 20% of flying planes may have these rockers, it was our intention to make a comment on them upon our return to Florida.

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We have not yet returned to our shop, we are still on the road, but in light of yesterday’s failure, we are issuing this Safety Alert immediately. The fleet of Corvair powered planes is less than 500 aircraft, and the number of engines built to our exact recommendations is a still smaller number. A single failure gets my attention and is worthy of comment, however, a second failure of the same part, even if it is one we do not recommend, warrants a Safety Alert.

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SUGGESTED ACTION: I highly recommend that all flying Corvair engines with the Chinese rockers remove them before further flight and replace them with cleaned and inspected original GM rockers. The failed rockers had 80 and 350 hours on them. These are roughly the equivalent of 2,000-4,000 miles of operation in a car. It is important to understand that this is not an “infant mortality issue,” and having 100, 200, or even 400 hours of operation on Chinese rockers without issue does not justify their further use.

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The rocker arm is a deceptively simple looking part, but it’s correct manufacture is a complex process involving careful quality control and very high levels of manufacturing expertise. By comparison, a small, but highly skilled shop of precision machinists can make a billet crankshaft, but it is highly unlikely that any small shop could make a Corvair rocker arm. The design is a deep stamping done under very controlled conditions. The GM rockers were done in several hits on a blank that was thicker in areas that would be stretched. The Chinese units appear to be made from uniform thickness blanks, which leads to very thin sections in the ball area. That is the location of both failures. GM units are twice as thick in the ball area. There will always be some fool to say that GM’s design was not good but this is pure BS; it is the most prolific rocker arm in history, also on almost every small block Chevy 1955-2003. We are speaking of nearly 1 billion rocker arms. Since 1978 I have owned about 40 cars and trucks. Other than 2 Buicks, every one of them has been a Chevy, a Chevy truck, or a GMC. They all had these rockers, I have never broken one. I have seen the inside of more than 500 Corvair core engines, and I am pretty sure I have never seen a broken GM rocker arm. If your local ‘expert’ tells you he has seen dozens of broken rockers of this design, nod politely, but understand he is dishonest and a liar.

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This is a “Safety Alert” and I am issuing a “Suggested Action” because Corvairs are experimental engines, and as such do not have Airworthiness Directives and Service Bulletins in the same form as certified engines do. I cannot require any builder to take any action, I can only appeal to his better judgment by making a serious recommendation. Airworthiness Directives are only issued by the federal government, and Service Bulletins are issued by certified part manufacturers, thus the difference in the Safety Alert.

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This said, I appeal to builders to follow this recommendation. The most frequent form of push back on suggestions of this kind is a builder who is myopically looking at his one plane and making a conclusion based on his impression of his own plane. Conversely I get to see all the data, understand the extenuating or aggravating conditions, I had world class training in statistical decision making at Embry-Riddle, and I always further consider what still works, not just looking at what broke.  I am not a genius, but for the above reasons, my recommendations on Corvair flight engines carry more weight than those of one guy with a flying plane, even a well intentioned one. We don’t have to speak of opinions of internet personalities that have no direct personal involvement nor experience with flying Corvairs.

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DISTRIBUTION: I ask that this information be shared with others who personally involved in building a Corvair flight engine. This should be done just by people who have read and understood the information themselves, who also are Corvair builders.  If someone named “Flyboy26″ shares this with an airframe builders group or a general pilot discussion board, and includes a comment like “no one should fly car engines” or “Corvairs break”, neatly deleting the Chinese source of this issue, you can be assured that their motivation for commenting has nothing to do with promoting safety or assisting others in managing risk.

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FURTHER READING:

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Pros and Cons of Roller Rockers

Chinese Crankshafts for Corvairs, update 2/17/13.

Cessna’s Chinese adventure a failure.

Communist Chinese government at Oshkosh

Mooney sold to Chinese, Fake endorsements.

 

Brand New 250 page 2014 Manual- Done

Builders,

I went to the print shop yesterday and picked up boxes of our new manual. This is a very large, entirely new Corvair Conversion manual I have been working on for 18 months.

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Rear view of a 3000 cc engine with mechanical fuel injection.

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It is based on the new numbering system that we introduced last year, It is much better organized than our previous manual. It has twice the page count, but it has a more compact font and smaller margins, yielding 3.5 times the content of the last manual, The word count is now 103,500. Every photo has a detailed caption, much of the book is in color, it has greatly expanded sections on installations and includes checklists and operations data.

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Grace has delayed mailing new manual orders that have come in recently to wait for this. If you bought a manual in the last 90 days we will get you a new one after Oshkosh for reduced cost. If you hold an older manual and would like to upgrade, just send us an email with “Manual upgrade” in the subject line and the number from the cover of your original manual please include your mailing address.  After Oshkosh we will send you a note about the cost of the upgrade before we ship it to you.

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New Builders can directly go to the manual link on our products page: http://www.flycorvair.com/manual.html to order their manual. We have raised the price to $69, from the $59 cost that we had on the last manual for 10 years.- ww.

 

 

Great moments in aircraft testing -2003-2004-2008

Builders:

In two weeks we will be headed back to Oshkosh. Once there we will be surrounded by hundreds of companies that will all attest on a stack of Bibles that they have carefully tested all of their products to protect the safety of their customers. In with these people will be at least 30 companies selling engines. Every single one of these companies will tell you without blinking an eye that their engine power output numbers are the result of careful Dynomometer testing. Almost all (90%) of these companies are lying about this.

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Traditional dyno testing is expensive, and a bit of a production to adapt an aircraft engine to. To learn much, it requires hours of evaluation, and runs at different conditions. Any company that does this would be justified in taking a photo of this milestone in their company history…….except you can politely ask to see a photo of their engine on a dyno, and of course they will not be able to produce a single image of their engine running on a dyno. I actually had one company tell they had done 100 hours of testing, but had forgotten to take a single photo of it. In an era where nearly every human has a cell phone that is also a camera, please tell me who would believe this?

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There are many kinds of dynos. Basically they all apply a load to the engine, and then measure the equal and opposite torque reaction resisting this load. No Dyno measures HP; they measure torque. HP is a calculation based on torque and RPM. If you building a plane, you don’t need to know this, but ideally everyone selling engines would, (but they don’t). A real motor head, like yours truly, knows this stuff. Combine this with some basic fabrication, and “Taa Daa!” the $500 dyno. Our dyno used the prop to generate the load,  allowed the engine to rotate on it’s crank axis by using a front spindle from a Corvair car, and measure the torque with a hydraulic cylinder. Later we simplified it further with an electronic scale for measurement. Using a digital optical tach, the accuracy measuring HP was within 2%

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I didn’t invent this kind of dyno, it has been around a long time, pictures of them in 1960s Sport Aviation magazines. This isn’t even the simplest kind of dyno. In one old Sport Aviation there is a picture of a Corvair  hanging on a steel cable turning a prop, with a wooden arm touching a scale. Yes that works also. The pictures of our set up have been on our webpage for more than 10 years. It would be very easy for any company selling engines at Oshkosh to have built their own version. Easy, but not as easy as telling people they have hundred of hours of testing, but forgot to take any photos.

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2003- Above, Oil system testing at Spruce Creek airport, 2003. We were testing how much pressure loss the cooler had when the oil in it was cold soaked for an hour at 32F. Testing like this is serious business. Note that Gus Warren liked Becks Dark, and I liked Michelob. Lot’s of companies like to have the appearance that they test products: they put people in lab coats and have them make scientific faces.  I don’t care for appearances, I just want results, and the picture shows we drank beer while we let the oil cool off. I can put on a lab coat a lot faster than a salesman can become a motor head and teach builders anything valuable.

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2004- Above, an O-200 on our dynamomemter; test crew from left to right, above: Gus Warren, Detroit Institute of Aeronautics, A&P 1990; Steve Upson, Northrop University, A&P 1976; yours truly, William Wynne, Embry-Riddle Aeronautical University, A&P 1991. While the way we dress may be slow to catch on in high fashion circles, we certainly know our stuff about all types of aircraft powerplants.

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2008- Above, Kevin and I are standing on my front yard, wearing jackets. We were 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 was actually  three occasions in four years when these conditions were met on testing days, and all our results we calibrated against these standards.

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How you can build a Dyno for $500 if you know how they work and you can weld:

Dynamometer testing the Corvair and O-200

A page devoted to all kinds of testing:

Testing and Data Collection reference page

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Questions from potential builders:

Builders,

Here are some questions that came in as comments on other stories:

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Frank Stephenson writes:

“While there will be many different results, I am wondering what the average time before overhaul may be. Also what are we looking at cost wise for one of these engines and the average cost of an engine mount? I am considering selling my current conventional geared C-172 with a C-O300B engine and buying or building something a bit smaller and more efficient. I really don’t know anything about Corvair engines other than I know of several folks who have utilized them, but I don’t really know anything about their results. I have found, in general, that automotive engines don’t make really good aircraft engines, but some VW engines I have known of are an exception and apparently the Corvair engines may be an exception.”

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Frank, the minimum time between overhauls on a well built engine is 1,500 hours. Ten years ago we listed 1,000 hours as a very conservative figure, since then, improvements like using valve rotators have driven the life span up significantly. The Overhaul cost on the engine is very low, on the order of $2,000 to replace almost all moving parts or recondition them. You can lean more at this link: Basic Corvair information I understand that many automotive engine engines have a poor record, but I have been doing this for 25 years, and we have earned an excellent one. You can read this link: Planes flying on Corvair Power, and see many examples. For the cost of motor mounts, just look at out catalog,http://www.flycorvair.com/, and page down to Group 4200, it lists the price of every mount we make.

I know VW engines have worked for many people, but I will put the track record for reliability, power and TBO of our work with Corvairs against any VW based engine. There is a lot of information on our main webpage, http://www.flycorvair.com/. I understand that it looks overwhelming, but better too much than to little.

Here is an important point: I don’t think efficiency is a good enough reason to move to homebuilding. Lets say your Cessna does 110mph on 8 gallons an hour. There are several Corvair powered planes that can do that on 5 gallons an hour, even some on 3 gallons an hour. But even if you were to cut your fuel costs on flying 200 hours a year from $8,000 to $4,000 per year, I don’t think it is enough motivation to send a guy to the shop for 1,500 building hours. The only people that consistently succeed at homebuilding are the people who inherently would rather fly something the personally built, and people motivate by the desire to learn new skills. I have met very few people motivated just to fly less expensively who thought in the long run that homebuilding was worth it. Consider this carefully, you may have a better time staying airborne in the plane you have.

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Steve Spears

“Sir, I am currently building a RW26 Special ll and I would like to use the Corvair engine. However, some people are telling me that it is to heavy for the aircraft. What are your thoughts and do you know of anyone who has used a Corvair engine in the Rag Wing aircraft? I read what you wrote about the Pietenpol and am encouraged that I can use the engine”

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Steve, I looked at this pretty closely for an hour the other night. I tend to think that a Corvair is too big to the R-26. The 912 appears to be as large an engine as people use. Several of Rodger Mann’s designs have flown with Corvairs, but I wouldn’t call any of them an ideal match. I am guessing that a Rotax 503 is really the optimum engine for many of his designs. For a comparison of how heavy duty a Pietenpol is built, the longerons in the fuselage are one inch square spruce from the firewall to the tail post. I am pretty sure the R-26 is lighter than that.

For any plane that you are wondering about Corvair power for, the best rule of thumb is asking if the same plane has flown with a Continental o-200. If it has, a Corvair will always work in it. For a comparison of the two engines look at this link:Corvair vs O-200….weight comparison and this one:Dynamometer testing the Corvair and O-200. We also have a lot of info on comparisons to 912s at this link: Testing and Data Collection reference page.  -ww.

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Turbocharging Corvair Flight engines Pt. #2

Builders, Here is part 2:

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“Boosted” engines: If normalizing is trying to maintain 29.92″ of sea level pressure in the intake, a boosted engine is driving the manifold pressure above this. This is actually very common, and almost every single classic radial engine was “Boosted”, except they most often used superchargers to do this. A P&W 450 hp radial is known by its displacement “the 985″ is how many cubic inches it has. They make their rated power at 36.5″ of manifold pressure. Many other classic piston engines made their power at 45 -72″ of manifold pressure. High end GA engines like the GTISO-520 makes it “low power” 375 hp rating at 40″ MAP. In the big picture it is ‘turbo normalizing’ that is the oddity.

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In the car, the turbo Corvair is a Boosted engine. The 180 HP ‘Corsa’ model made its rated power at 5,200 rpm and 45″ MAP. That is about 7 pounds of boost in car-speak. Worth noting is that the same engine made 265 foot pounds of torque was down low in the rpm band, at a setting that can be used in a direct drive engine, and the turbos we have used are far better at building torque that the car original was. A 3,000 cc  engine running 40″ MAP on takeoff is burning the same amount of fuel and air as a 4,000 cc naturally aspirated engine. If that doesn’t sound dramatic, read this story to understand what kind of difference 35% more power makes on a plane’s climb performance: Pietenpol Power: 100 hp Corvair vs 65 hp Lycoming

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Draw through vs Blow through:  On a draw through arrangement, the air flows through the carb, then the turbo and on to the engine.  A blow through is turbo-carb (or injection) and then the engine. Draw through is characterized by simplicity. Our set ups are all draw through, as was the original Corvair car. Virtually all modern cars are fuel injected, and the ones that are turboed are blow through. The primary advantages are two things which don’t matter to planes, throttle response and emmisions.  One of the hidden advantages to draw through is the fuel getting fully vaporized early radically cools the intake air and makes it more dense without the need for an intercooler. Injected engines can’t do this because the fuel arrives in the intake just ahead of the valves. In one minute at full output, a turbo engine will digest and vaporize more than a pound of fuel, this has a great cooling effect on 250 cubic feet of air.

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One of the things that always comes up when you mention draw through arrangements on planes is an alarmist pointing out that every foot of the intake has air and fuel in it under slight pressure, and this is in his mind a giant fire hazard. A dozen years ago it was mentioned on the Dragonfly builder’s list that I was working on a draw through arrangement for the Corvair. The leading ‘personality’ on that list wrote a long diatribe about what a horrible person I was, and convinced most people of this by saying that no airplane was made that way.  Only one problem with his argument, it  was a complete lie.  The US built 300,000 planes in WWII; 160,000 of them were multi engine, and 32,000 of those had four engines. If you look at all the radials, the Allisons and the Merlins on these planes, You are looking at 750,000 engines, and virtually every one of them was a draw through arrangement being boosted by a turbo, a supercharger or both.  A R-4360 engine has at least forty, (40′) feet of intake piping after the blower, and every bit of it is packed with fuel and air. There are 56 couplings in that intake system that I can think of. If draw through systems didn’t work WWII would have had a different outcome.

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 For a look at some of our ground testing we did in 2004 before flight testing, get a look at this link: Testing Turbo Corvair and Rotax 912S. In some of the tests we ran the MAP all the way to 60″, which is 15 pounds of boost, or a 2,700 cc engine inhaling the same amount of air as one that is 5,400 cc (330 cubic inches) The turbo we were using was a modified Garret TO-4B with a .58AR housing, machined for a carbon seal. It worked great. Not all turbos are expensive, this one was made in the USA and it was only $545 brand new. The real cost of a full turbo system is far more, because many of the other parts like the exhaust system have to be made from very high quality materials. If you look at the price of turbos on Ebay, be aware that the market is flooded with counterfeit name brand turbos that are made in red China. A turbo counts on good materials, it often runs 1,600F on the inlet and the wheel is turning 100,000 rpm while it is working. If it breaks a blade or bearing, it feeds the metal from the compressor side right into the engine. It pays to buy the real thing, especially because the US made items are often reasonably priced.

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 We learned a lot in testing. My plan was to take the regular 2004 100 hp conversion on the Skycoupe and run it with the turbo on it and get some time on it to see what parts would need to be upgraded to last on a turbo engine.  First, let me say that nothing on the engine broke, but judging from the 1550F EGTs and high oil temps, the engine would have gotten ‘tired’ quickly with the stock conversion parts of 2004.  When I see people talking about putting a turbo on an engine out of a junkyard that was never intended to be turboed, I can only wish them good luck, because our testing indicated that any engine running in a boost condition will need the best available internal parts and systems.

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Below is a number of things our testing indicated we needed for the engine to work as a regular, long lived power plant. After each topic is a link to a story of the part we developed to address each of the issues. These developed systems also served as stand alone options that have improved regular naturally aspirated Corvairs, but the owe their origins to conditions our testing identified 10 years ago.

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Engines in lower compression and more displacement with a quench: The 2,850 pistons were developed specifically to work with turbocharging. They also happen to work very well as a dual fuel piston suited to both 100ll and auto fuel. The 3,000 cc models we developed as a spin off. read the stories by clicking on the links:

Getting Started in 2013, Part #16, 3,000 cc Piston/cylinder kits

Getting Started in 2013, Part #14, 2,850 cc piston/rod/cyl. Kits

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Pressure retard distributor: When an engine is boosted it need less ignition advance. This is done on a Corvair car with a pressure retard in the place of the vacuum advance on the stock distributor. In the Skycoupe I made a special dual points distributor that only had 25 degrees of total advance. The long term answer was the system below. As a tech spin off it will also be useful on naturally aspirated engine at very high altitudes:

Ignition system, experimental “E/E-T”

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Ultra high grade exhaust valves: We normally use 4-N stainless valves in Corvairs, but the exhaust valves of turbo motors need to be made of exceptional materal to last to a normal TBO. This is a job for the super-alloy Inconel. Mark Petz of Falcon head fame developed these in 2008.  See picture below:

Above, I hold the last word in Corvair exhaust valves. In the past year, Mark Petniunas put a tremendous amount of effort into finding a source for these valves, which are precision manufactured out of the super alloy Inconel. It has greater strength at 1,500F than 4130N steel does at room temp.

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321 stainless exhaust. Our normal exhausts are made of 304 stainless, a very high quality material, but the job is better done by 321. Very few experimental engine companies have ever used this because it is 3 times the price of 304. The link below is about our regular systems, at the bottom of this page is a photo of a 321 system I made for a 601XL test.

Stainless Steel Exhaust Systems

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high volume oil pumps: Turbo engines need more oil flow to feed the bearing in the turbo, the 5th bearing and to internally cool the engine. High volume oil pumps have been around for a long time for Corvair cars, but we developed our CNC model which has better internal alignment:

High Volume Oil Pump

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large aircraft oil coolers. Turbo engine make the oil hot, it flows through the turbo’s bearing with is one inch away from the exhaust housing which can be visibly glowing. Our Gold oil systemens serve many purposes, but they would serve a turbo engine very well and allow the use of a appropriate sized cooler:

Heavy Duty Gold Oil Systems, new cooler model.

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5th bearings: These were in development by the time we were doing our turbo testing, but we did not have one on the skycoupe. Today, virtually all Corvair flight engines use one, and I would not consider building a turbo engine without one:

Getting Started in 2013, part #1, Crankshaft process options.

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I am holding the turbocharger that Woody Harris found for our test program. Note that it has an integrated wastegate. This is a common feature on modern car turbos. However, almost no modern car turbo has the capability of being used in a drawthrough application, which is a highly desirable format for aircraft use. It took us a long time to find an expert on turbos who could properly fabricate a modern turbo, appropriately sized for our application, with a carbon seal. 

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I built this exhaust System out of 321 stainless. Its future home is on Woody Harris’ 601 XL.   He will be retrofitting his 2,850 cc engine with a turbocharger. This is the engine half of the exhaust system, and it was built in my jigs. Our regular exhaust systems are built out of 304 stainless, which is extremely durable and fairly resistant to heat flow. 321 is the alloy of choice for Turbo Systems, as it withstands elevated temperatures even better. Notice how the one pipe crosses underneath the engine to go over and meet with the other before heading into the Turbo.  It is worth noting, however, that naturally aspirated Corvair powered 601s with 2,700 cc engines have exceeded 17,000’ and have little problem with density altitudes over 14,000 feet.

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