Ignition timing on Corvairs, Part 2

Builders:

Eighteen months ago I wrote a comprehensive story on ignition advance and timing on Corvair flight engines. I consider the story one of the most important and fundamental elements of mastering your Corvair. If you have not seen it in a while, or you have joined up since then, I suggest making 15 minutes in your schedule to read this and give it your full attention. The story is here: Ignition Timing on Corvairs.

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I use the term “suggest” above because I am my brother’s keeper, but not his jailer. I care about people, but I can only appeal to their willingness to learn and do a good job, their ethical responsibility as an airman to take risk management seriously. I can not force anyone to do anything with their own property. If you would like a real world example of this, we have this story from last year: Understanding Flying Corvairs Pt. #6, 98% DNA not enough. In it you can read about a person who destroyed his plane on it’s first ‘flight’,  severely injuring himself and a passenger, simply because he didn’t care to understand timing, long refused to buy a timing light, and refused to stop what he was doing when I warned him.

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For Part 2 , a slight update: On the internet, there is a suggestion being made by a non-pilot, that fliers using Corvairs should only use 24 degrees total of ignition advance on their planes, because this will allegedly make the same power as using the full advance we recommend. After 25 years of doing this, building several hundred Corvair flight engines, countless tests and having spent 5 years of my life at Embry-Riddle, I an assure builders that they should simply follow my timing recommendations for best results. To offer some further ‘why’ to expand the understanding.

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Ignition advance isn’t magic, it is Chemistry in action, particularly a branch of study in it called ‘rate of reaction.’ While I am not a Chemical Engineer, I was fortunate enough to have a number of classes with Dr. D. Cameron at Embry-Riddle, and he was an outstanding professor who really understood and could teach the physical properties of this branch, and he also knew internal combustion engines very well. This doesn’t make me an expert, but compared to a guy who slept through 9th grade Chem class, I am Alfred Nobel on the topic.

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How long it takes to burn the air and fuel in the cylinder, and thus how much ignition advance the engine needs, is a rate of reaction problem. Combustion dynamics in a real running engine are very complex, driven by the fact that once the combustion starts, the reaction itself is changing the dynamics of remaining unburned fuel and air. This acknowledged, the principles still apply, and they can be seen in action and tested easily for their proportion and effect.

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I could list 10 factors playing a role, but let’s look at just two of the ones that make using too little ignition advance an issue:

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The lower the pressure in the cylinder, the more advance it will need to make full power: Rate of combustion is greatly affected by the pressure in the cylinder when the spark happens. Three factors on this are the compression ratio, how wide the throttle is open, and what is the atmospheric pressure outside. While a max power test on a high compression engine, at sea level with the throttle wide open, may show OK results with less advance, That isn’t how planes go flying. Lower the compression to what most builders are using, understand that much of flying is cruising at part throttle, and the critical item a car mechanic never sees, the reduction of atmospheric pressure as the plane climbs, all call for more ignition advance for the engine to make best power and run efficiently.

The lower the starting temperature (given the same density)  the more advance it will need to make full power: While cold dense air burns fairly quick, cold thin air does not, and it needs more ignition advance to run efficiently. Again, this is a common factor to planes that few car mechanics consider. As a plane climbs it will do much better with even a slight increase in timing. Many people know that Klaus Savier’s Vari-eze is one of the most efficient homebuilts ever made, particularly in any contest where he can get some time at altitude, and he primarily credits his ignition that has far greater total timing than the magneto it replaces.

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There are plenty of myths about aircraft timing. I have people tell me every year that “aircraft engines all have 25 degrees advance” Really? evidently this people missed all the manufactures data working A&P mechanics use. Look at this Mandatory Service Bulletin from Continental:   http://www.tcmlink.com/pdf2/msb94-8d.pdf  Notice how the A-65’s all use 30 degrees of advance on both mags. People tell hangar stories about ‘the big bore of aircraft engines needing two plugs’ ignoring the idea that an O-200 continental’s piston is just 5/16″ larger in diameter than the one in a 3,000cc Corvair. The internet theories are endless, but mostly based on things easily disproven on inspection.

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Limited timing does appear on some other engines, like Jabarus and some VW’s, but this is driven by the mechanical design of those ignitions. Such engine are not noted for easy starting nor high altitude efficiency. Some people tout that Continental reduced the timing on O-200’s years ago, but his was actually driven by pilots using auto fuel that didn’t meet the STC requirements, and doing damage to the cylinder mounting studs on certain models. Car mechanics don’t know this, but ask anyone who flew a 150 before and after the timing reduction, and they will tell you the 4 degrees Continental ‘dumbed down’ the engine made a power difference.

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On it’s face, saying the Corvair makes full power at 24 degrees doesn’t make sense. What would GM, the original manufacturer use far more advance than this if that was all it took to make full power? Even the most torque oriented Corvair engine, the 95hp model, which had a peak torque at just 2,400 rpm and made it’s full rated power at 3,600, arguably closest to the flight engines we build, used 32 degrees of total advance (with the vacuum advance disconnected). If the engine made full power with 24 degrees, GM would have made them that way.

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The only possible motivation for a car mechanic to recommend using less ignition advance is if he is concerned about an engine having been assembled with substandard parts, like Chinese valves, and he is trying to convince people to lower the power output to protect the cheap parts. This also applies to telling people the engine can not fly with cht’s that touch the 400’s like this: CHT info taken from test flight of 601XL  Many of the issues where builders have been told they hurt their engine by running it to hot and be re-evaluated. There have been plenty of builders who made poor cowling choices who damaged engines, but we have positive evidence and factual data that shows the Corvair can run the CHT at my recommendations, provided of course, it doesn’t have sub standard valves in it.

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Above, a closer look at an E/P distributor in my distributor machine ( circa 2008). The machine has a large electric motor inside that spins the distributor. I have made hundred’s of Corvair ignition systems over the years.

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From  Ignition Timing on Corvairs :

“If a builder reads and follows the directions, he has mastered level 1). If he reads, considers and understand this story, he has moved his understanding up to level 2). Does he need to know more than this to effectively use the engine? No, but if he would like to know far more, it is one of the things I have a good understanding of in engines. This did not come from years of being a mechanic. The further understanding came from a number of years in Engineering classes at Embry-Riddle, Particularly the Chemistry classes. While the subjects we studied were academic examples for almost all of my younger classmates, I was 26-28 years old then, and the information was enlightening when I had a sudden understanding of combustion dynamics that I had observed for years in automotive racing, but didn’t have a detailed view of how the factors worked together, far less that you could make calculated and predictable changes.”

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Above, as you see it, this is a non-running model, but it has a serious purpose. The red parts you see are plastic, and were made for us by Corvair/Panther builder Paul Salter. Read the story here: Ignition system, experimental “E/E-T”

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Running your engine “Over-square”?

Builders:

There is a long standing piece of “hangar wisdom” That says you should never fly a plane “Over-square” . This condition is defined has having a higher manifold pressure in inches of Hg than you have RPM in  hundreds. Example: 25″ map and 2400 rpm is said to be “over-square”, where as the reverse, 24″ map at 2500 rpm is said to be “under-square”. This rule is brought up primarily to warn pilots about putting the engine in a condition where it might be prone to detonation.

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Like many things said in hangar stories, there is some element of original truth in this, but it doesn’t apply to all engines nor conditions. In the end it was supposed to be a little memory device for those unwilling to understand the larger principle.

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The origins of the statement are of attributed to being a good way to run Lycomings, or more particularly Lycomings with constant speed props. Over time, the “over-square” rule became something that people tried to apply to any engine in any situation. But a basic look at a trip around the pattern shows that the rule doesn’t work, not even in Lycomings; If you are near sea level and begin your take off roll at wide open throttle, your map will be darn near the outside air pressure, very close to 29.92″ on a standard day. Since no direct drive Lycoming with a fixed pitch prop turns 2990 rpm static, every take off is “Over square.” Even Constant speed equipped planes have redlines between 2700 and 2800 rpm, and thus would still be “over-square on take off.

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So what protecting these over-square planes from detonation on takeoff? Something very simple. Aircraft carbs, by design, run rich at wide open throttle. In private pilot school many people were told this was for “Fuel Cooling” the air-cooled engines, but that isn’t what is going on. The mixture running rich at wide open throttle effectively increases the comparative octane of the fuel. When you look at Octane ratings of old fuels like 80/87 or 100/130 or 115/145, these dual ratings reflect the comparative detonation resistance both lean and rich.  regardless of it’s name, any fuel will have more detonation resistance when the mixture is rich, and aircraft carbs set properly do this for you.

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Lycomings and continentals are configured this way, and if you have a properly set Stromberg or Marvel carb on your Corvair, it will do it also. However, you have to remember that it is always preferable to run the carb wide open when it is heavily loaded, ie, “Over-square”. Never let anyone talk you into backing off the throttle slightly on climb out, it is a very poor practice.

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The way to make sure your carb is set correctly is to tie the tail of the plane to something solid (not just chocks) and run the engine up to full static rpm. Give the engine a few seconds to stabilize, and then just barely pull the mixture out slightly. If it is set correctly, the rpm will increase as you lean it out, because you are going from an anti-detonation air/fuel mixture of say 10:1 toward best power at 12:1.  The power goes up, so the rpm will climb slightly. This is a good condition. If your carb doesn’t do this, it isn’t set rich enough. You can also watch this on your EGT.

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Where the warning comes into play is avoiding running an engine over-square in cruise settings where the throttle is partial open, and there is no additional richness to suppress detonation. Many times people refer this condition as “Lugging” the engine.  With Corvairs, I consider it very important that the engine turn at least 2,700 rpm static with the prop pitch set for flight. This way, on every take off and climb out, The engine will be operating close to “square” which minimizes the chance of detonation, and additionally the engine has substantially better seat of the pants detectable performance with just 100 more rpm static.

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Some builders, particularly Pietenpol builders like bigger wood props that often yield low static rpms in the 2400-2550 rpm range. I feel that this is an undesirable condition because such a prop tends to “lug” the engine, not just restraining it’s performance, but it is prone to cruising in a condition of low rpm and higher manifold pressure, but without the carb being in the wide open throttle position. Many guys feel that flying around with a larger wood prop at lower rpm is easier on the engine, but I can make a pretty good case that just the reverse is true, especially if the builder ever runs car gas.

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More Rpm will not hurt the Corvair, keep in mind that it did more than 5,500 rpm in the car and was designed to cruise in the car over 3,000 rpm. Your aircraft engine is far better built than any stock Corvair Car engine from the factory, so more rpm will not hurt it, but loading it at lower rpm just might.

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-ww.

 

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Above, a new 2,850 running  on the test stand in our front yard. During the cam break in period, (20-30 minutes) We run the engine between 1800 and 2200 rpm. The throttle is only part of the way open to do this. During the later part of the break in runs we run the engine as high as 3,200 rpm. At that condition the MA3-spa carb on the run stand is wide open and the O2 sensors and the egt’s indicate the engine is in the anti-detonation rich zone. Read more at this link:  New 2850cc / 110hp Corvair in photos.

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Center, above Joe Foss (USMC-CMH) stands with Charles Lindbergh in the south Pacific in WWII. Lindbergh was a factory rep for Vought, and one of the things he taught pilots was how to get extremely good range by running their engines massively “Over-square”, (very low rpm, high blower and high prop pitch) It worked, but the training included elements of making sure the air/fuel was very rich. Foss went on to be the Governor of South Dakota, Commissioner of the AFL, host of “The American Sportsman” and president of NRA.

Compression Ratios, Fuels and Power Output

Builders:

Here are three topics that are related. Although the conversion manual covers this in some detail, I will put a short summary here.

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We have 3 popular displacement s for Corvairs 2700, 2850 and 3000 cc (read more: Sources: Choosing a displacement.)  The latter two are made with a very special dish in the piston to lower the static compression, but keep the ‘quench area tight. On any of these displacements you can either put lower compression 95 hp heads, or you can put higher compression 110 hp heads. Right there you have six combinations with different compression ratios, but it is also possible to build engine with high or lower compression, but those six are the popular ones, and having the option allows Corvairs to suit different builders purposes.

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The two basic rules are: The higher the compression, the more power the engine will make….and There is a limit to how much compression you can use with car gas. The commentary here is general, but it comes running engines on our own planes from 7.7:1 compression (1998 2700 engine in our Pietenpol) to 11:1 compression (2005 3100 engine in our 601XL) I write this as a guideline, if you have a specific application, feel free to ask in the comments section.

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Basically any of the three displacements with 95 hp heads will have compression ratios from 8:1 to 8.5:1. Engines built with 110 hp heads will have ratios from 9.0:1 to 9.5:1. The variation is mostly in the machining done to the head gasket area, and the actual gasket thickness.

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The First question is what is the lowest Octane fuel you will ever use in your plane? In the answer is “I will never put anything but 100LL avgas in my plane” then you can use any compression ratio you like up to 11:1. Your engine will make about 5% more power for each whole point you raise the compression. But….you can never, not once, ever, run the engine on car gas, even 93 octane car gas if the compression is much over 9.5:1. 100LL is great fuel. yes engine can be detonated on it, but this is done by leaning the motor out far too much or not having the timing set correctly. Our 11:1 compression engine flew more than 600 hours on two different airframes The first 200hr was 11:1, we dropped it slightly to 10.5:1 for the rest of its time) It never detonated at all, and it never saw a drop of car gas either. 100LL when running slightly rich has a comparative octane of nearly 120.  Keep in mind that many people swear they will use nothing else, but later after the 40 hrs. are flown off, some people start getting cheap, and the are tempted to run car gas in a 9.5:1. They might get away with it under some conditions, but sooner or later, they will pay.

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Let’s say you are going to run ethanol free 93, or some mixture of this and 100LL, how high is smart to go? You could run up to 9.3:1 and get away with it, as long as you don’t excessively lean it. But what is the benefit of running on the ragged edge? If your engine is built with a ratio of 9.0:1, there will be hardly any measurable performance difference, but it will have a large increase in resistance to detonation.

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What about running 91 or 92 Octane car gas? Then it seems prudent to shoot for the lower range offered by using 95 hp heads. I have never been interested in speculation on what “should work”, I am much more interested in builders developing enough judgment to understand they are far better off with set ups that have a greater margin of safety than a slight performance edge.

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Examples:

Woody Harris , who’s plane is pictured below, started flying with a 9:5 to 1 compression 2700. (Flat top pistons and 110 hp heads). Because he was planning on switching to a Turbocharged installation, he went to an 8.25:1 2,850. (dished pistons and 95 heads). Woody had enough fun flying around, that he didn’t get to turbocharging. Woody has long reported that the power output between the high compression 2700 was about the same as the low compression 2850. This isn’t a surprise. Woody mostly flies on 100LL, but if he or anyone else was planning on running 91-92 octane fuel, they would be vastly better off with the lower compression 2850.

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My own 3,000 cc engine: Is set up at 8.3:1 compression (dished pistons and 95 heads) Although it might make 6 to 8 more hp if the compression was raised to 9.5:1, I don’t care because I am not running 100LL, my choice is to run ethanol free boat gas, which here in Florida is 90 octane and sells for about 10 cents a gallon more than 93 with ethanol. This week that is $2.80 a gallon. This is a very clean burning fuel and  it stores for a long time. On a cross country the engine will not care if it drinks some 100LL, again the compression ratio is determined by the lowest octane you will use, not the highest.  A few more hp isn’t going to make the Wagabond into a speed demon, I am after absolute long term reliability and being able to run any fuel available.

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Ron Lendon’s 2,850: Ron built a clone of Woody’s 2,850 engine with dished pistons and 95 hp heads. Recently he changed to flat top pistons and 110hp heads. This changed his compression ratio from 8:1 to 9.5:1. Yes, this will make more power, and it is OK because Ron says that he only runs 100LL . In short, he didn’t start with the highest performance option for the fuel is was going to use. Ron has worked for GM in their enginnering department for decades, so perhaps like most people who saw fuel prices in 2009, he might have been thinking about auto fuel then. But it pays to plan around the fuel you will eventually use. To keep things in perspective, I am sure that a 601 with a low compression engine and wheel pants met a 601 with high compression and no pants, the one with wheel pants might be faster.

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In the above photo, Woody Harris’ 2,850cc Zenith 601B sits at the end of the ramp in North Carolina at First Flight Airport with the Wright Brothers Monument in the background. Woody’s home airport is in California. He has nearly 500 hours on the plane without issues. read more:Woody’s 2,850cc Corvair/601XL hits 400 hours.

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Woody in the Grand Teton National Park WY

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Lest anyone think that low compression engines don’t make good power, above, Woody flying over Grand Teton. He often flies around the Sierras, and has flown to the highest and lowest airport in California in the same day.

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Above, a drop forged, made in the USA piston for the Corvair. The  displacement of this piston is 2,850 cc. read more: Turbocharging Corvair Flight engines Pt. #2

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2005 photo of our 601XL in front of our Edgewater hangar. The engine is a 3100 cc with 140 hp heads, oversized exhaust and 11:1 compression. Because it was a tail wheel and low drag it was fast. With wheel pants and the right prop turning 3,500 rpm, this plane could exceed 145 mph at sea level. People asked about weight, but at the 601’s low wing loading, it is slightly faster when loaded. They are good planes, but other than demonstration purposes, anyone really concerned about getting the last mph out of a 601 probably picked the wrong plane. It beauty is in utility, not speed. Note the size of the inlets: Here we have the most powerful Corvair engine that builders have heard of, yet it cooled itself just fine in hot Florida with 4.75″ inlets and a front alternator. It is a myth that this installation needs giant inlets to cool itself.

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Same plane, at sun n fun 2006. Sensenich prop was faster, but didn’t climb as well. I could have built the same engine for the plane we have today, but instead I chose something on the other end of the compression scale because I don’t wish to be tied to 100LL forever. Take your pick, what ever makes sense to you.

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Above, Dr. Andy Elliott, of Mesa AZ with the same engine on his 601XL. The photo was taken at Oshkosh, so it is safe to say the plane flew without issue. Andy flew the engine another 400 hours. His state has the highest summer temps of anywhere in the US, and yet the high performance engine cooled through the same size inlets. Andy’s plane could do nearly 140 mph. The power was a factor, but aerodynamics matter more and are cheaper. Before selling the engine to Andy, I reduced the compression slightly, but he still knew to always run 100LL.

-ww.

Sources: Group 1500 – New cylinder head source

This is part seven in the ‘new sources’ series.

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Builders,

In the numbering system of our conversion manual, the cylinder heads are Group 1500.  Over the years, a very small number of builders did their own rebuilding, but the great majority of builders bought heads that were complete and ready to bolt on.  The conversion manual has a short history of how the heads we have used evolved over time. In 25 years, we have had 4 different primary suppliers. Today we have a new one that we recommend, and that is the Weseman’s at SPA. https://flywithspa.com/corvair/.

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The Corvair above has heads made here in Florida. So does the 3.3L engine in this film:

https://flywithspa.com/the-stroker-engine-is-here-see-video/

Having a steady flow of high quality production heads, the same for heads for builders, and heads for projects like his 3.3L engine motivated the development of a reliable source here in Florida. This is nothing new, between 1996 and 2005, every head we put on an engine was made here in Florida.

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Starting last year, I told builders that ‘we’ were developing a second source in Florida, because Falcon Machine, our previous head shop, had fallen way behind and had lead times ranging from 12 to 24 months.

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The ‘we’ in the above paragraph refers to myself and Dan Weseman. We jointly had a number of sets done in Jacksonville, while doing about 50 to 75% of the prep work in our shops. Dan’s motivation was that he had sold nearly 50 Panther kits, and a third of these people are planning on Corvair power. Dan asked Mark if he would produce these heads, but over 20 months he didn’t even send the first set.  For my part, I have complete engines to build, and Mark had only made me 2 sets in 2 years, and he was producing only a small number for builders. No conversation could motivate him, so it was time to develop another source.

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After extensive effort, It was apparent that Dan has greater resources, particularly with their bigger labor force, and it would be better if he ran the new head program 100%. I loaded the entire back of my pickup full of my core head collection and drove it down to the SPA shop, and I also sold my core collection at Falcon machine to Dan, who is having it shipped to Florida.  Dan is very serious about producing very high quality heads, in quantity, and eventually having many sets of them on the shelf, that any builder can buy without waiting.  This will be a radical improvement in the world of Corvairs. Just as with other parts, I have no financial incentive to endorse Dan’s heads, they are just a better option for builders.

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Lest anyone find this unfair to Mark at Falcon, let me take a moment to remind them that no human on planet earth, has said more good things about Mark than I have. If you look at his website, and the writing sounds familiar, it is because I wrote every word of that also.  Over 10 years of knowing him I brought him to many colleges, to our booth at Oshkosh, and my countless stories brought him plenty of work and justifiable praise, but in the end, it didn’t motivate him much.  In recent years his snails pace of production left many people who ordered engines from us angry a slow deliveries, while Mark often made heads for engines he could sell himself lucratively.  It is another case where he could have just stuck to his main product, heads, but he chose not to.  I had many good times with him and friends are important, but one person is not more important than dozens of builders who have put great effort over years to build and fly their planes.

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Below, a serious issue: Three valves from Corvairs. On the left is a $9 valve, OK quality, not the best choice in top quality heads. Although he once installed Inconel valves in engines, Mark was unwilling to invest $8K in a production run of them, so he reverted to the valve on the left. ( $8K isn’t a big amount of money to invest in a main line aircraft product, Grace and I spend 20 times that in materials in an average year. )

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On the right is a stock used original GM valve. It came out of a Corvair core at Barnwell that had 100,000 miles on it last year. At the event, Ken Pavlou burned out a valve just like the one on the left. We replaced it with the old GM valve as a field repair. We didn’t grind it, just lapped it by hand. Although it is used, almost 50 years old, and went flying 100 hours, it is actually in better shape than the one on the left, because GM put better valves in it than $9 buys today. Ken mailed his heads down over the winter, and I replaced all the valves with high quality ones, the same make that Dan uses in his heads. Cost: $240. Ken’s plane has much better compression. It flew to Oshkosh and is running great. Quality parts count.

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In the middle, a Chinese valve with 30 hours on it. This was actually installed in a set of heads By Roy at Roy’s garage. Get a look at the split in it. Roy made a $1200 set of heads to replace ones that had flown for 5 years with reground GM valves. The new valves only lasted 30 hours. In discussing it before I saw the heads, Both Mark and Roy were adamant that it must have been something the builder/pilot was doing. They made this claim even after seeing the heads. Neither of them is a pilot, and the person they were accusing of causing this has several thousand hours, and about 250 in their Corvair powered plane. I explained to them that I didn’t believe the pilot was doing anything different. When I got to see the valve, and understood that the issue was a $5 Chinese valve, but the two of them still wanted to believe that all problems are caused by pilots. Eventually I found out that this wasn’t the only time they had seen the exact same thing, but they had stuck to the story that it must be the builders fault. The automotive world can afford such attitudes of infallibly, but there isn’t room for it in aviation.

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“Phase IV Heads” – A good joke.

Mark from Falcon and Roy’s Garage have teamed up to promote a ‘special’ head modification they want to charge builders an extra $500 for. They call this “Phase IV”.  Since Mark never got his dyno working, they ran it on Roy’s simple one, and they claim it makes great magical power increases,  It did improve Ron Lendon’s 601, but that plane didn’t run well to start, and now it is as fast as a regular 601. But here is the inside joke: Mark and I have seen the original 1979 Mad Max countless times. A great apocalyptic fiction film. Watch the you tube clip below at :23 where Barry the mechanic says “Phase IV Heads”. Great stuff, but the movie was fiction, the blower on the car was fake, and there is no such thing as “Phase IV heads”, unless you need to talk people into waiting another year for heads or sending their heads back to have the Chinese valves quietly removed, for the modest cost of $500.

https://www.youtube.com/watch?v=VpDLeo4lcCg

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-ww.

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Sources: Group 1100, Camshaft.

This is part six in the ‘new sources’ series.

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At Oshkosh this year I had a guy stand in my booth and tell me he was part of an on line discussion group about Corvairs, and they were using an idea called “crowd sourcing” to come up with “new answers.” Because of my superior anger management training, I was able to calmly explain that 50 people who have never built a running Corvair speaking to each other on line is a form of the blind leading the blind, and it doesn’t work any better in Cyberville than it does in reality. I also said that Cyberville may seem great because everyone gets to have their own unicorn, but he should remember that even if he brings a lot of he video game “extra lives” from Cyberville when he heads to the airport, “Game over” has a different meaning in reality than it does in his pals in the Sony Play station world. He made a hurt face when I said “You can go ahead and press “reset” but me and my friends Physics Chemistry and Gravity will still be here. Reality works like that.”

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The  little gem above is about an actual conversation I had with a  guy at Oshkosh 2014. This is an excerpt from my original post about our complete Group 1100 package. You can read the original story here:

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1100-WW Camshaft Group

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Above, the elements of the #1100-ww Camshaft group package. It contains every required part in the 1100 group in the new manual numbering system. Everything in this picture is made in the United States.

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In keeping with the ‘sources’ nature of this series, I will cut to the chase and remind builders that you can order the complete 11oo group from us for $400.  The Conversion manual contains the full story on cams, and the link above explains the issue with loose thrust washers from car cam suppliers. Getting the whole thing from us makes these factors a non-issue.

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We have had these cams for a while, and they are well proven in a number of flight engines. This year, the package has proven to be very popular, particularly at colleges. A number of builders have pointed out that this group doesn’t yet have a link on our product page of our traditional website. I know this, and let me say if you need one of these just send us an email with “1100” in the subject line. Our original website is written in HTML, and is difficult to update, but we are working on a revised one, with much better clarity and written in a much more friendly format for computer morons like me.

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-ww.

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Sources: Group 1000, Crankshaft

this is part five in the ‘new sources’ series.

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Builders;

Ok, so far in this series on accelerating your engine build, we have followed the basic path that builders go through:

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First, a look at working with the best sources for progress:

Revised sources, listed by Group numbers, Aug. ’15

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Second Decide what 5th bearing to use:

Sources: Choosing a 5th Bearing

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Third, Decide what displacement to build:

Sources: Choosing a displacement.

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Fourth, review the first milestone, getting to a Closed case:

Sources: Closing a case

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Now lets move to looking at the Groups individually. The first one in the conversion manual is Group 1000, the Crankshaft group.  While it is discussed in great detail in the Manual, the focus here is on where do you have it processed if you want to make progress on your engine? This question has one simple answer: You have your crankshaft processed by the Weseman’s ( https://flywithspa.com/corvair/ ) or you buy one of their new USA made Billet Cranks. The have processed exchange cranks on the shelf, and you can begin your engine build this week, not next year.

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Above is a close up of a Gen II Weseman bearing journal on a re worked GM crank. The Gen II arrangement comes already installed on the crank, match ground in place. This is the correct choice for progress. After torqueing the case halves, the housing installation is a simple matter. It isn’t a speed contest, but I have personally done them in under an hour. First time builders at Colleges do them in 3 hours all the time. The Weseman’s have a simple loaner tool kit available, and I have my own I bring to Colleges. Buying these parts, and putting them together with your own hands is what the core of the Corvair movement is about. This is a far better option for progress than sending your case off to an alternative 5th bearing with a multi-year waiting list.

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Deciding to work with the Wesemans for your crankshaft is a natural. They are serious enough to have carefully developed a very detailed process, and now send cranks through it a dozen and a half at a time.  I was impressed enough with their methods that I took the crankshaft out of my own personal 3,000 cc engine and replaced it with  another GM crank that went through their process, simply because The Wesemans processing involves an extra step of stress relieving the crank before working on it, and this is an undeniable improvement over previous methods. They are the only people working on Corvair cranks who do this.

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The Wesemans process Gen II bearings for the same cranks, so you can make one call to them and send in your core crank for an off the shelf process exchange crank, that already has a specific, serial numbered,  5th bearing that has been matched to that crank. It is one stop shopping, with very little wait. Having these two elements will cover both Group 1000 and Group 3000 in your build. This is the smart choice if you want to make progress.

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You can review their website in detail, or contact them to review pricing and options. They also have Billet cranks, and they are evaluating the stroker Billet crank which is at the heart of their 3.3 liter motor project.  While the Billet cranks are very fine pieces of machinery, about 90% of the engines going together at Colleges are Gen II Weseman bearings that have exchange GM cranks that were processed by the Wesemans. Read the background on their site, either one is an excellent choice.

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Just to head off any suggestion of this from people who compulsively assume that every suggestion they read is a paid endorsement, I will state for the record that I pay full price when buying cranks and bearings from the Wesemans, including paying Florida sales tax, which means I actually pay more for the stuff than builders living in the other 49 states. If this is someone’s idea of a clever monetized endorsement strategy, they need a new conspiracy theory.  I recommend these parts simply because they work, they are available, they are a good value, and they serve builders goals. It is that simple. In the long run, all of those things also serve the reputation of my work making the Corvair a viable American made option for homebuilders.

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-ww.

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Sources: Choosing a displacement.

This is part three in the ‘new sources’ series.

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Builders:

The second decision to be made when building an engine is which displacement to use. The Corvairs Pistons, Rods and Cylinders are covered in Group 1300 and Group 1400 in the conversion manual. Here are the ‘Common’ displacement choices for builders: 2,700 cc’s,  2,850 cc’s and 3,000 cc’s.

( Additionally there are two other displacements on the availability horizon, 2,775 cc’s and 3,300 cc’s. )

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The conversion manual covers the choices in great detail, and we have links below the pictures to specific stories for builders who would like to read more in detail. To stay focused here, I want to concentrate on where a builder goes to get the parts for each of the Groups involved.

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2,700 cc: Traditionally, these parts are ordered from Clarks Corvairs in MA. ( http://www.corvair.com/user-cgi/main ) . Clarks offers two brands of forged pistons, and all the specific part numbers are contained in the conversion manual. We have always guided builders directly to readily available source rather than trying to ‘middle man’ these parts.

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2,850 cc: We have been selling these kits for a number of years, and they are flying on a large number of aircraft . In the last 24 months, we have had trouble getting the proprietary new cylinder that these kits are based on. This has caused delays in deliveries. We can still get them in a trickle, but in the long run I am working to replace this option with the 2,775 cc kit, which is based on the original 1965-69 GM cylinder. The 2,850 kit pricing is on our page : http://www.flycorvair.com/products.html

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3,000 cc: The person who originated this displacement and kit is Dan Weseman. Not only did he place the original piston order with R&D costs, it was his particular experience base and flight testing that refined the design and set the displacement. Although I have sold 3,000 cc kits, and I have used the same machine shops here in Florida for the work, I am now steering builders buying a 3,000 cc kit to get it directly from Dan Weseman at his site: https://flywithspa.com/corvair/ .  He has invested to buy a great number of piston sets, several hundred cylinders, and he is the source for new billet connecting rods. He also has on the shelf, exchange cases pre-machined to the 3,000 cc cylinder size. The pay off is that any builder can now just buy the parts right off the shelf.  I will still be building complete production 3,000 cc engines, but when I need the parts to assemble one I will just get the from Dan, just like builders .

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As a courtesy while he was focused on developing the Panther aircraft, Dan Weseman allowed Mark at Falcon and Roy’s Garage to order the piston sets off his original design card. In order to insure interchangeable parts, Dan, Mark and Roy agreed to a set of dimensions for the machine work on the cylinders, but each of them had cylinders made at a different location. Although it would have made more sense for Mark and Roy to try to get caught up on their backorders on heads and 5th bearings respectively, they didn’t choose that path. In the end, they, as one person shops were spread too thin to do any of the jobs well, and they don’t have the resources to stockpile parts and kits on the shelf. Thus, any builder who wants to build his own 3,000 cc engine without long delays should just get all the Group 1300 and Group 1400 parts from Dan Weseman.

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Above, Dan Weseman and I at the test run of his 3,000 cc Panther engine. No person flies a Corvair harder than Dan. His engine has performed flawlessly through a full 18 months of aerobatics. To Learn more about 3,000 cc engines read these links: Why Not the Panther engine? and The Panther’s engine, worlds strongest Corvair flight engine.

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IMG_2296

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Above, a 2,850 in my front yard. I built this particular engine around a Weseman billet crank, thus,the only used parts in this engine are the case halves, the head castings, the oil case casting, the distributor body and some misc. hardware. The rest, including the cylinders, pistons rods, crank, and all conversion parts are brand new. Read more here: New 2850cc / 110hp Corvair in photos. to read a bout the first 2,850cc engine, now with hundreds of flight hours, read this: Woody’s 2,850cc Corvair/601XL hits 400 hours.

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 Above, Dan and Rachel stand on either side of their 3.3 engine at Oshkosh.  Read the story at this link: SPA / Weseman 3.3 Liter Corvair now running

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Above, our 601XL pictured at Brodhead WI in 2004. The first 200 flight hours on the plane were done with a 2,775 cc Corvair that we specifically built to test the displacement.  The combination offers a slight power increase over a 2700 cc engine, but is specifically aimed at using standard automotive gasoline. We are bringing this combination back to an off the shelf kit in 2015.

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-ww.

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