Cylinder Head Temperature measurement
Builders;
In this story I would like to address CHT (Cylinder Head Temp) measurement on Corvairs. In the 20+ years I have been working with Corvair flight engines, I have written a great number of informative posts and stories on this topic, and I have also covered this in stories on cooling systems, instrumentation, human factors for lower time pilots and how CHT relates to detonation threshold.
My comments on these topics can be found in our manuals and on both websites. The information we have shared is from personal measurement on several of our own aircraft, dozens of test engines in extensive ground runs, comparative instrumented engines, and a data from a number of experienced Corvair powered pilots Like Dan Weseman and Woody Harris. All of this has been collected and correlated with my professional A&P perspective, and often discussed at great length with other trained professional aircraft mechanics like Gus Warren and Arnold Holmes, whose experience includes extensive Corvair flight time, in addition to many certified aircraft engines. My data includes many aircraft that worked well, and a handful that didn’t. It is big picture, not myopically gleaned from looking at one or two engines, listening to stories and jumping to a conclusion.
I do not consider myself ‘brilliant’ about this topic. The value of my perspective comes from simple observation of data over a long period of time, working with builders and being in the best position to gather all the data. This is the opposite of just following a few stories that seem to support a pet narrative. Part of what motivates this story is hearing from builders who have been told a number of myths about Corvair CHT info.
One builder was told he “Has to have 6″ air inlets.” Others have been told that the GM CHT locations don’t work. None of this is supported by observed data, it is opinion from people who just think their pet theory is right. The myths are not always malicious in origin, but well intentioned and malicious myths are both myths just the same. Two very prolific sources of this information are people jumping to conclusions based on little experience. If someone has never soloed a Lycoming, Continental nor Corvair powered plane, they can still have an opinion on CHT, it just isn’t worth sharing with builders who need factual, unbiased data.
Above, a Lycoming O-320 (160hp) cylinder that I own. The 320 is the most respected and prolific light aircraft engine ever built. You are looking at the bottom of the cylinder, the 320 has both the intake port (left) and the exhaust port (right), on the bottom of the head. The arrow points to the CHT probe location. One of the people telling builders his view that under plugs was the only place for CHT obviously didn’t know that all Lycomings use this location, which is very much like the GM Corvair location. For most Lycomings, the CHT limit is 475F. While I am thought of as a Corvair guy, Our hangar also contains a C-85 and an O-290, and parts of many other aircraft engines. My perspective comes from broad experience and spending time with aviation professionals with far better backgrounds.
A mechanic may be clever with EFI or experienced with vehicles imported from the fatherland, but if they have never turned a wrench on nor flown a Lycoming powered plane, their perspective is myopically limited. I really don’t know a lot about modern car maintenance, but I do know a fair amount about planes, and I know enough about both subjects to say that knowing one does not qualify you in the other.
On the table next to the cylinder is a 50 page Lycoming operations manual. You can down load it for free off Lycomings website. Every aircraft mechanic I know owns a copy and is familiar with the data inside. It is a great book, and even as a Corvair guy you should read it. Quite often, people will say things that are directly against the experience in this manual, even when they are Lycoming owners, speaking of Lycomings. For example, Dan pointed out to me that Lycomings leaning operation in the book is enrich it until it runs slightly rough and lean it only until it runs smooth, exactly the opposite of what most people think. Either you are the kind of builder who is inclined to follow the recommendations of the company that built 300,000 of the engine you are running or you are the kind of guy who is going to follow a story written in Flying magazine by a guy who has never pulled a cylinder off any aircraft engine.
For several years at Oshkosh there was an alternative engine guy who’s background was car racing who liked Gear Driven liquid cooled V-8’s. He started all of his forums by writing on the board “If Lycoming made a car would you drive it?” I spoke with him a number of times and read the stuff he wrote. He absolutely felt he had nothing to learn from Lycoming, (or most other experienced sources for that matter) He doesn’t write that any more. This is because he was killed by a mechanical failure while flying his plane. It was his second major accident. He killed his passenger also. I spoke with him after the first, and I will tell you he learned nothing from it.
Another person using that same engine wanted to put it back in production, after the accident, but he was killed by a similar engine failure. I just read a nice magazine story about a very nice Australian aircraft using the same gear box. A small postscript at the end of the story said that he was killed by a gear box failure. Same magazine had a press release from a new guy who bought the gear box assets to make more of them. You don’t need a crystal ball to predict the next chapter.
Don’t have anything to learn from Lycoming? They made plenty of successful geared engines like the GO-435, the IGSO-480 and the IGSO-540. No, they didn’t make cars, but evidently being a ‘race car driver’ doesn’t qualify you to make geared engines either. People who claim that they don’t have anything to learn from the successful experience of people who preceded them tend to attract followers with the same mindset. A harmless social phenomenon when the topic is flower arranging, interior design, modern dance or fashionable footwear. When the topic turns to subjects with consequences, like aviation, builders who plan to die at home in bed with all of their great-grandchildren in the next room, tend to learn from others.
Above, the GM Corvair CHT location. Most common question: “Is it on the same spot on both heads?” Yes, because there is only one head. There is no such thing as a right or left Corvair head until we weld the pipes on the intakes, so this is on “both” heads. In 95 and 110 engines it is threaded 3/8″-16. An easy way to put CHT here is to use a 10MM spark plug ring CHT terminal and hold it down with a 5/8″ long bolt with a washer. This will work great. All Corvairs with the exception of ‘Spider’ and ‘Corsa’ high performance models had an idiot light in the dash that was tripped at 575F by a sender screwed into this hole. I had a guy who had never owned a Corvair tell me that the 10mm ring would not work because “it needed to touch the bottom of the hole” Really? the GM sending unit didn’t, and it read just the same.
For another view of a Corvair powered plane that is slow climbing, but runs cool, read this story: Gary Burdett, 2,850cc Zenith 750, now flying. (engine selection) I personally verified the temps that Gary is getting by independently measuring them in person, on his plane, at Corvair College #26. I heard from a guy who said he didn’t think it could run that cool, that both Gary’s instrumentation and mine must both be wrong. This comment came from a person who has never seen the plane nor the engine, has no idea where the temps were taken from, nor does he have a running engine nor a pilot’s license, yet he is still quite sure he is correct, unwilling to even entertain the possibility he is wrong. Some people you are just not going to reach, and that is OK. Plenty of people who stayed on land back in Spain felt that if Columbus had just sailed a little further, he would have fallen off the earth, and nothing Columbus did was going to change their minds.
Above, an eight year old photo from the old hangar in Edgewater. In the foreground, my 1966 140HP four carb Corsa, behind it Kevin’s 1965 180HP turbo Corsa. Both of these cars have factory CHT gauges. The factory turbo cars did not use a waste gate, they just had an oversized turbo and a very specific muffler, and the result was a very simple system that did not go into boost until the car had some serious rpm, the throttle mostly open and the CHT over 400F. Below this, the head dissipates the heat energy the turbo needs to make boost. The engine will not make its full output until it is up in the 500F range. Granted, they didn’t have to run this way for a hour at a time, but I have met people who don’t believe that Corvair engines were run that hot in the cars without damage. They hold this opinion even though they have never driven a turbo Corvair and seen the CHT gauge with their own eyes. I have driven 120,000 miles spread over the 4 Corvairs I have owned. At the time the Photo was taken, Kevin owned 7 other Corvairs, Grace had her 65 van, Gus had a ’67 Monza and Dave had a ’69 Monza. I felt that our ‘hangar gang’ was qualified to comment on Corvair operation. I have met many people who have never owned a Corvair with strong, but incorrect opinions about how the engines ran in cars. Explaining the basis of my observed experience to the contrary, they often stick to their opinion, they are more comfortable with any antic dote that seems support their opinion than a mountain of contrary evidence. This is especially true if the person in question is a car mechanic.
Corsa models, (140 and 180 HP) have the hole threaded 3/8″-24, same as a Lycoming. To make the 95 heads on my plane compatible with standard Lycoming probes, I have helicoiled them for 3/8″-24 threads. The probes I am using are Electronics International P-101s with A-101 quick detach fittings. They are in the Aircraft Spruce catalog on page 523.
If a guy wants to share an opinion about temp measurement that is contrary to mine, it might be worth asking what kind of test equipment he us using. If he looks at the head of an engine he did not see run and wants to jump to a conclusion, or he wants to use internet data from a builder who never set the timing with a light or is running a non aircraft carb, it probably isn’t going to be as accurate as I can collect in person.
From my tool box, top row, Fluke two channel digital type K temp meter, accurate to less than 1/2% of reading, compares two probes simultaneously, reads all common aircraft probes. Digital type K contact thermometer, 0-1,200F, accurate to 1 degree. Westach CHT, common in aircraft, not accurate source of info, but commonly quoted on net. Bottom, two Raytech non-contact thermometers. accuracy limited to surfaces that don’t have shiny finish, tends to read too high in many circumstances. OK for quick check looking for cold cylinder, but weak on data gathering. Small spark plug item: Original AC thermistor from 140/180 HP Corvair. Same part actually used on many certified aircraft such as Twin Comanche.
Above, the instrument panel in our Wagabond, in the process of being wired. The gauge in the lower right is the CHT. It is a very accurate military unit with a little stamp on the back that says “Calibrated MCAS Cherry Point.” It takes type K thermocouples and need no power at all to read, it is independent of the electrical system of the plane. There is a hole under the gauge for a left /right switch.
I like traditional gauges, and 2 CHT’s in the stock location make sense to me. You can also run 2 CHT’s in the stock location with many Glass Cockpit displays. If you want to run 6 CHT’s, then you are probably going to run them under the plugs. If you do this, know that we have gathered plenty of data to say that these will actually run hotter than the CHTs in the GM location because they actually read the temp of the plug as much as the temp of the head. They can be a little pain during a plug change, and if you are not careful, you can over torque one in a plug hole with a helicoil or a time sert in it, and the sending unit will stick to the top of the thread and extract it when you unscrew the plug. One way to avoid this is to run a copper washer, then the sender, then the plug, but this is even more likely to show the temp of the plug. I have wired plent of planes for 6 CHTs, I am not enough of a zealot about it to really care about what other people would like in their planes. Dan has 6 CHT’s under the plugs in the Panther and it works great.
In general, the plug temp on #1 will read 60-80F higher in climb that the same cylinder with a probe simaltainiously running on the bottom of the head. If anyone is speaking of CHT’s on a Corvair, and anyone comments on it without first establishing where the temp was taken and what kind of gauge was used, then they are not adding anything to the discussion. Quite often, if a builder mentions that their plane runs hotter than they would like, the first thing people like to chime in with is that there must be something wrong with the way we teach people to build cowls and cooling systems. In reality, we have people who are flying the same system successfully, so logic say to check these this first:
1) Is the timing set correctly with a light?
2) If there is a significant L/R difference, especially at part throttle, and it has a flat slide carb like an aerocarb, Elison or a Rotec, it is the carb causing this effect. Butterfly style aircraft carbs don’t do this.
3) Does the cowl have inlet rings?
4) Does the outlet have a lip on it and is it 3X the size of the inlets?
5) Is the instrumentation correct?
6) Are they the correct spark plugs?
7) Is the fuel high enough octane?
8) is it a one of a kind prop? (these frequently don’t pump much air down near the inlets)
The above 8 points are the most common factors that keep the engine from running as cool as possible. Be advised that I have seen people break all 8 at the same time and still fly their plane without overheating it. God protects children and usually fools also. If you like the image of being 100 and meeting your great-grandchildren, I suggest not trying to discover the exact statistical value of “Usually.” -ww
3,000 vs 3,100 cc Corvair engines.
Builders,
A number of builders just getting into Covairs miss the distinction between these two engines. Below I have a number of links to illustrate the difference, but in a nutshell, the 3,100 was the “big bore” option on corvairs between 1998-2008. It has since been largely superseded by the 3,000 cc Corvair with good reason. There are still a number of 3,100s flying, and there will be for a long time, but very few, if any new ones are being built these days. A number of builders who previously flew 3,100s have elected to build a 3,000 as their next engine. There are reasons for this, and I will detail them below.
Above, the 3,000 cc Corvair that is flying in the Panther prototype. Notably, Dan Weseman successfully put several hundred hard hours on his 3,100cc engine in his “Wicked Cleanex, ” but opted for an all-out 3,000 cc Corvair in his aerobatic Panther. The engine both cary the same 120hp rating, but the internal differences make the 3,000 more durable, and it is far easier to build.
On the surface, the difference between a 3,000 and a 3,100 is simple: the 3,000 has a 92mm bore and the 3,100 has a 94mm bore. But the details go far deeper. The 3100 was originally developed for dune buggy’s in California, and piston/rod cylinder kits were sold by a number of companies in California. I bought one from Bob Sutcliffe in 1998, and his quality was good. At early Corvair colleges we assembled at least 15 and perhaps as many as 20 of these engines. It was very apparent that the quality of the kits varied a lot. The other issue was that builders who knew nothing about engines spent lots of money on poor kits from California, and them brought them to Colleges and said “I just spent $5,400 with a dune buggy place that has never seen an airplane, and now I would like you to build this for me for free this weekend.”
The main problem with this was several fold, first, ‘free work’ isn’t what colleges are about; second, these engine required a lot of hand work and fitting to even be assembled. Often they had no standardization, and individual pistons and cylinders could only occupy specific locations on engines. The big one was that each of these engines required a custom set of pushrods to be made so the valve geometry was correct. We and others like Mark Langford repeatedly told people that this was not a first engine to build. Most people listened, but there was a certain type of person that just wanted a bigger engine although they were unwilling to learn the required detailed information to understand and assemble it.
Internally, the 3100 had many VW 94mm parts in it. Here are the things about that that I didn’t like: The pistons, even good ones made by Mahle, were cast. The VW wrist pin is 22mm, and the dune buggy mentality was to just bore out the Corvair’s .800″ (20mm) rod to take the larger pin and run it as a steel on steel no bushing floating pin. This worked, but was a poor way to do it. The California companies would occasionally send out a rod with a .060″ wall thickness around the pin and think nothing of it. These engines also had the head gasket cut so large that it broke into the upper head bolt areas. Using the VW pistons made the compression height wrong for the Corvair, requiring custom pushrods to correct it. The Compression on these engines was really too high to safely have Mr. average pilot run car gas in it. Many of the people attracted to them didn’t recognize that Mr. average pilot was a polite name for them. If you would like to read about 3100s that worked well, look at:
KR-2S at 700 Hours – Joe Horton
and:
Zenith 601XL-3100cc Dr. Andy Elliott
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Above is the 3100 of Dan Weseman in the Cleanex. This engine and the one in Chris Smith’s ‘son of cleanex went on to log about 500 hours each. Note the reverse gold oil filter housing on the engine. Have a look at four 3100s taking off in a row from Corvair College#16 in South Carolina, Langford, Weseman, Smith and Horton:
http://www.youtube.com/watch?v=JK23b-BWptE
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The first Correction actually came from Brady McCormick, Owner of the now defunct Magnificent Machine. What Brady did was have a new forged piston made in 94mm. This was a good idea, and he incorporated the Corvairs deck height and pin diameter in his design, automatically correcting the geometry. But it still had the head gasket issue, and the piston design Brady chose was a light weight one for high rpm engines. It’s compression was still high, and It could not tolerate having a dish machined in it. Still it was an improvement, and perhaps 15 engines were built this way. Examples would be Jim and Rhonda Wesemans Celebrity; Mike Robitie’s Cleanex engine;( Guest writer: Phil Maxson, flying a 3100cc Corvair in his 601XL ) and several production engines we built like this one: http://www.youtube.com/watch?v=y_1ov0DAbe8&feature=plcp
Brady’s pistons are no longer available, and the forging blanks they were made from have been acquired by Clark’s Corvairs as the basis for their USA made forged pistions. (They are only made to .060″ over bore now, and 94mm is a .264″ overbore)
Above Jim and Rhonda at CC#23, with Dan in the cockpit. the engine in this plane is a one of a kind reverse rotation Corvair, a 3100 with Brady pistons. Jim is a life long professional aircraft mechanic by trade, and a very clever guy. He had the experience to create a very unique Corvair for his plane. Most builders are far better off building an engine that is a regular “bolt together” experience. Jim and Dan developed their 5th bearing as a father/son team. Jim and Rhonda make Corvair cowling and baffling kits, but they made their best contribution to experimental aviation back in 1975…by having Dan.
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The actual permanent solution was having a better forged piston made, and reducing the bore to 92mm. In doing this we went to a different American manufacturer that specialized in pistons with thicker crowns that could have a dish milled in them. Below is a look at the 3,000cc piston top in a bore along with the head is designed to match.
Above, a 92mm/ 3,000cc Corvair set up. This is the final evolution of the big bore Corvair for aircraft use. Note how the head gaskets don’t break into the stud holes. The flat area on the head and piston are referred to as “the Quench”. There come very close to each other, making the charge burn much quicker with much less chance of detonation. The dish in the piston keeps the static compression low, ideal for running on car gas or 100LL.
The 3,000 cc engine is a far better engine for builders to work with. Although I can build any Corvair engine I like, and our 601XL had a very strong 3,100 in it, I didn’t hesitate for a second to switch to a 3,000 cc engine for our Wagabond. People who only know a little bit about engines often think that loosing 100cc is going backward, but in reality I typically de-tuned our 3100 because it had cast pistons and what I considered excessive compression. On the Wagabond’s 3,000 cc engine I am setting up to run at full power for as long as I like without having to retard the timing for car gas operation. Let this serve as a basic introduction to how the 3,000 cc engine has surpassed the 3,100 as the dominant big bore Corvair flight engine. For more 3,000 cc stories follow the links below.-ww
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World’s Strongest 3,000cc Corvair, built by Greg Crouchley
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Panther Prototype Engine 3,000 cc/120 hp to OSH
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3,000cc Engine Running
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Getting Started in 2013, Part #16, 3,000 cc Piston/cylinder kits
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Flying Zenith 750 w/3000cc Corvair, Doug Stevenson, California
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3,000cc/Billet Crank Shortblock, Destination: Waiex
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New 3,000 cc Cleanex, Dale Williams, SC
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Corvair vs O-200…. weight comparison
Builders,
A Zenith 701 builder that I spoke with at the open house wrote me a short note asking some questions about the weight comparison between these two engines. This is something I have directly compared, something we have very good data on, and some valid and useful commentary.
For people with short attention spans, I will cut to the chase and say that a modern Corvair, as we teach people to build them, with electric start and a charging system, weighs the same installed as a standard O-200 Continental. You can see in the photo below that I have weighed, thrust tested and dyno run them side by side personally. Many people will comment on the subject of engine output and weight on power plants they have never laid a hand on, far less run on a dyno. Most of the “evidence” people present is well intentioned, but erroneous just the same. Bad data, presented with good intentions or malicious ones, is still bad data. The numbers here come from personal measurement, intentionally done in public for people to see.
“More Lies are told in experimental aviation than in singles bars” is a saying I made up 15 years ago to illustrate the loose association with truth that many people in our field have. The most common fib told in home building is under quoting how much something weighs. (This is ironic, because compared to numbers like HP output, true stall peed, or ultimate G strength, the weight of anything is a very simple matter to check, but very few people ever do.) Many people I quick to point the finger at salesmen, but let me also say that I have done the weight and balance on something like 100 homebuilt aircraft, and only found 10% of the owners were remotely telling the truth on their W&B sheet. Many of these people told their buddies their plane was exactly 100 pounds lighter than is was. Frequently they repeated it often enough that they forgot they made it up, and could have passed a polygraph test swearing to it. Take this away: Don’t believe anything you hear about weights unless you are listening to the guy who did it himself, who has photo documentation of him doing it. If you would like to read a funny story about how reality has a hard time competing with fantasy, take a moment to read this link:
Unicorns vs Ponies.
On the left above is the Continental O-200 as removed from a 1959 Cessna 150. This engine is considered the standard against which all other 100hp class engines are measured. It is a direct drive 4-stroke, 4-cylinder engine of 200cid. It carries a horsepower rating of 100 at 2,750rpm. I have read that Continental produced about 50,000 O-200s. On the right is a 170cid Corvair engine. For size comparison, the O-200 is 32″ wide without the baffling. The Corvair is 28″ wide.
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The caption in italics above is actually nine years old from our main page flycorvair.com. It is from a long test series on dyno and thrust testing the O-200. You can read the full story at this link: http://www.flycorvair.com/thrust.html . The picture above shows that a Corvair is smaller physically than an O-200. Let me also offer that I know a bit about Continentals and I like them. Graces Taylorcraft has an STC’ed C-85-12 in it, an engine that is nearly Identical to an O-200 in physical size and weight. Keep in mind that when people compare engine weights on the net, very few of these people have owned both of the engines they are commenting on, and in many cases, the guy offering the data has owned neither. It doesn’t make then bad nor evil, it just means their data on this subject probably isn’t good.
What about the often quoted 188 pound weight for an O-200? That is erroneous, as it does not include the starter, mags, plugs, carb, oil, or many other items it takes to run the engine. The data was actually presented that way so if a manufacturer chose Eisman mags instead of Bendix, he could do a weight and balance engineering solution on the engine. The 188 number was never meant to be a comparison all up weight.
What about the new light weight O-200? Yes, it is lighter than a traditional model, by as much as 20 pounds. But this engine, which Continental rep. Kim Winner brought to the Zenith open house, sells for $20,000. It is new, and they have made very few of them, and you are not likey to come across one for sale used for another 20 years. Many of the parts in it can not be used on older engines. Most builders are taking about a Corvair they could build on a $8500 budget vs a traditional O-200 taken from a Cessna 150 for roughly the same money. If you want to spend $20K, I can build you a Corvair that is far lighter than the lightest O-200 ever made. Given $8,000 or $10,000 just to spend on weight reduction, much could be accomplished, but that isn’t an engine most people are considering, and neither is the new light weight O-200.
Is an O-200 ‘Approved’ for a 701 but not a Corvair? You can call Zenith and speak with Roger or Sebastien, and I am sure that they would advise any 701 builder to first consider lighter engines. But they would also tell you that both engines have powered 701s before. We bought our 701 test bed kit directly from the factory in 2005 and completed it in 2007. Sebastien sold it to us to test the concept after seeing the success of our 601/Corvair program. The 701 worked. we made no attempt to lighten the Corvair for it, and the plane weighed 677 pounds ready to fly. (if that didn’t sound very light compared to other numbers you have read on the net, go back and read Unicorns vs Ponies again.) It did not need any ballast whatsoever to get into the CG envelope. On this last point, the Corvair has a distinct advantage over the O-200; The Corvair is ‘flat’ on the back, and can be pulled right back to the firewall without creating a maintenance issue. An O-200 has the mags and wires sticking out the back, and they require several more inches of clearance to be removed without the requirement of pulling the engine off the mount. Although the Corvair and the O-200 effectively weigh the same, you can’t get the O-200’s CG nearly as close to the firewall. It may require ballast just to get into the front of the CG range.
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Above, Our test bed Corvair powered 701 in the Zenith booth at Sun n Fun 2010.
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I have heard that a heavy engine can break the 701 nose gear, truth? Yes, a very heavy engine could be a factor, but when we built our 701 I studied this closely, and a far bigger issue was people flying the plane forward of the published CG envelope. One guy had tried a Geo engine with a belt drive on a 701. This was actually lighter than a Corvair, but the engine layout was very long, and it had to be positioned well forward to clear items from the firewall end of the engine. The result was I guy flying around 2″ ahead of the forward CG limit. The plane could be landed smoothly by rolling it on at 60 mph, but that wasn’t the point of the 701. When the Geo guy tried landing slow and pitched the nose up, he found out that planes that are ahead of the forward CG limit drop their nose like a rock at high angle of attack. This is the effect that harms the plane. It is actually a CG issue, not a weight driven one. Poor pilot technique is another big factor. Any guy willing to get a little time in type training and fly within the published CG range has little to worry about.
What about reasonable cost Corvair modifications to reduce weight? A 3,000 cc Corvair actually weigh 7 pounds less than standard ones becase the bigger engine uses a lighter aftermarket cylinder set. A billet crank is nearly 4 pounds lighter than a stock one. A welded pan is a pound lighter than a billet one., etc. There is a list of parts than can get 15 pounds off a Corvair, but most builders find the engine to be acceptably light in the basic form. People frequently ask about putting aluminum cylinders on Corvairs. I have been working with Corvairs for 25 years, people have been talking about these for at least 12 years, and yet no one has ever taken a set flying. I have good reason to doubt the would work. If some one tries to talk you into anything that has never flown, and the national expert doubts will work, realize they want you to be a guinea pig. They sell down at the pet store for $20, and if your life is worth more than that, don’t be anyone’s Guinea pig.
Last Comment of weights: Two people in the alternative engine game, myself and Robert Helms, president of UL power, never hesitate to tell the truth about how much our respective engines weigh. Robert has nothing to loose by doing so; He has the lightest engine on the market, he doesn’t need to embellish the facts. In my case I don’t have anything to gain by under reporting the weight of a Corvair. People choose the Corvair because it is affordable, smooth, a learning experience, well supported, made in America and a multitude of other reasons. It has the features above, while having an acceptable level of weight for a broad variety of aircraft. If I fibbed about the weight of the engine I wouldn’t attract any significant amount of new builders, but it would undermine the trust and rapport with builders we already have in place.-ww.
College engine build options for closing the case
Builders:
Back in January I wrote a 20 part series on getting started in engine building. The first milestone that builders are working for is closing the case. In the new numbering system, this covers groups 1000, 1100, and 1200. In these stories, we are also looking at 5th bearing options, so we are also looking at groups 3000 and in the case of the Eddie Easy engine, Roy’s bearing, which is group 3100. I named each of the engines in alphabetical order, in the older, pre-NATO code.
Notes:
1) I later changed the numbering system slightly after these stories were written. For example, a crank is now part #1001, not 1000 as written in these stories. Small change, but I wanted no part to have the same number as the group it was in. Almost nothing else is changed, but as you are planning the details of your build, look for this number shift. The price sheet on our main products page has the final correct number system.
2) If you are going to build a 3,000 cc Corvair, the cases have to be bored out to accept the larger cylinders. If you would like to build your case at #27 as a 3,000 case, you need to mail your cases to me in advance of the college, (say by October 12 or 15th) and we will bore them out for $200. When you later purchase the piston/rod/cylinder kit, we will deduct this from the total kit price.
3) the most common short block that builders close at the college is a Gen 2 Dan bearing/ 2700 or 3,000 on a GM 8409 crank. Both reground and stock cams are common. Today builders interchangeably use OT-10 cams from Clarks Corvairs or CC-10 cams from California Corvairs. They both work.
4) I prefer that the cam gear clamp the thrust washer tight against the cam. A long time ago, Clark’s had a batch of thrust washers made that had no inner chamfer, which meant that if you pressed the cam gear tight, you would invariably introduce run out in the gears. I ruined 4 gears in the old Edgewater hangar in a single night working with Kevin before we spotted that the washers didn’t have a chamfer. A later inspection of Clarks installed gears showed that they had compensated by not putting the gear tight to the thrust washer. The correct fix, only took 60 seconds per washer….I put them in the lathe and cut the chamfer. After I told Clarks of the issue, they stuck to the story that they intentionally wanted the washer loose, but did later send out the washers in a revised form with the chamfer. Which is a long and old story that leads us to…….CC#26 where I ordered several washers from Clarks, and promptly got ones without the chamfer, and at the event I saw a Clarks installed gear with a loose thrust washer again. Since they didn’t really see this as a problem last time, perhaps the best solution is letting us put the cam gear on for you.
5) The California Corvairs and LS billet gears are made in the USA. A number of parts sold by Clarks are “GN brand” which is Chinese. This includes the stock gear. They switched them over years ago. The first ones they got were trash. Since then, I am forced to admit that these gears do work. The CC billet gear is very tight going on a cam, you must watch how far your key is sticking up, it can drag on the top of the keyway in the gear. I talk about avoiding Chinese parts, but I suspect that very few people really care. I recently got an EAA hat with the “heritage” logo on it. Yes you guessed it, made in China, sold by the EAA for $18.99. I was going to write something about it, how it told me that the EAA was interested in maximizing profit instead of exercising values, but I have been speaking of this stuff for years, and lets face it, very few people care. A friend just pointed out that the Chinese government is now a major shareholder in ICON aircraft. Read the press release that says they are going to be built by Cirrus, which itself is owned by the Chinese government….Yesterday brought news that Continental, owned by the Chinese government, was pressuring the FAA to issue a killer AD against their major competitor, the US founded and owned ECI. by my guess, less than 5% of the people in aviation care that this stuff is going on, so to whom am I speaking to anyway? I am convinced that 50% of Americans would see nothing wrong with buying a Chinese sewn American flag from Wal-Mart, just as long as it was a buck cheaper. I am happier when I don’t think about such things.
Below are the example short blocks. You can click on the links to the stories just below each listing. Write in with any question you may have, I am going pack to putting up all the mail sack comments in the next day or so.-ww
.
Engine options with 5th bearings:
Allan Able = $2,062
(See part #5)
Getting
Started in 2013, Part #5, ‘Allan Able’ short block.
.
Bob Baker = $2,516
(See part #6)
Getting
Started in 2013, Part #6, ‘Bob Baker’ short block
.
Chas, Charlie = $2,770
(See part #7)
Getting Started in 2013, Part #7, ‘Chas. Charlie’ Short Block
.
Davie Dog = $4,270
(See part #8)
Getting
Started in 2013, Part #8, ‘Davie Dog’ Short Block
.
Eddie Easy = $3,157
(See part #9)
Getting
Started in 2013, Part #9, ‘Eddie Easy’ short block.
Last call on crank processing before CC#27.
Builders;
I spoke with Dan and Rachel tonight, and they pointed out that this next week is the cut off for getting your core crank to them so they can process it before CC#27. I picked up several at CC#26, They already have several to batch with them, and they are only going to hold this until Thursday of next week, If you are planning on heading to the college, and you would like to make some serious progress like closing your case, it starts with getting your crank processed. I wrote a very good overview of the process in January, it is at this link:
Getting
Started in 2013, part #1, Crankshaft process options.
You have time to get your core apart over the next few days, get it wrapped up and on its way to their shop. If you know that you are going to do this now or later, just decide right now that you are going to get this launched now, so that you don’t find yourself as an observer at the college when everyone else is putting their engine case together.-ww
Above is a close up of a 2nd Gen Dan bearing journal on a re worked GM crank. This is a 2700/2850 ready case we put together and sold to Irv Russel at CC#24.
Deal Of The Day, early generation hub…(Sold 2:11 am, 9/3/13)
Builders:
Today’s deal of the day is an early generation black hub / starter and alternator arrangement. These parts actually flew on our Zenith 601XL in 2004. They have been used on another test engine. The parts are used, but in fairly good condition and airworthy.
