Month: February 2013

Builders.

There has recently been some discussion on the net about people flying Corvairs in cold weather. Specifically some builders were concerned that you have to warm up the engine for an extended period, and people were wondering if this could be shortened by having a thermostat of some sort. Some of the tone of the conversation suggested that these were conditions that might never have been encountered before of something I was never involved in testing. Neither of these assumptions are true. I have long known every detail of the Corvairs oil system, and it application to flight engines in great detail. Anyone who would like to learn more on this can write me with any question, review the sample of data taken off our website, or they can come to any college. Asking questions on the internet and sorting through various replies is not as efficient use of time if your goal is to build, finish and fly your plane. If you would like to hear a variety of opinions from people whose data is derived from zero to one Corvair engines, ask the net. If you would like to learn facts from years of testing, ask  me. It’s your time and your engine, you decide how to spend it.

First of all, the Corvair has an outstanding oil system. Think of how few core engines ever seen have any kind of damage inside, in spite of having 100,000 miles on 1960s quality oil and few changes in the last years of automotive operation. The work we have done to develop flight oil systems in evolutionary on top of this foundation. If you would like an overview of oil systems, read the link just below. Note it is from our website nearly six years ago. Still think there is an aspect of the oil system I don’t know? You are probably going to change your mind by the end of this story.

http://flycorvair.com/hangar1007.html

When you start a Corvair below freezing, you want to make sure that it is getting oil to the bearings. This is accomplished by having an oil cooler bypass and having thin enough oil for the bearing clearance. The issue that some people are concerned with is that it takes a Corvair or a lycoming for that matter, 6-9 minutes at an outside temp of 25F to get the oil up to 140F. How fast the temp comes up is not a real issue to the engine, but having circulation is vital to not hurting your engine.

Oil clearance; An engine that has .002″ main bearing clearance at room temp will have less at 25F. Why? Because the case is aluminum and it contracts more than the steel crank. This is a function of diameter. The bigger the diameter, the more starting clearance is required for very cold weather operations. This has been long known and understood in aviation. If you were told that German Aircraft engines didn’t start at -20F on the eastern front because of paraffin based oil, you were largely told a myth. A much bigger factor was bearing clearance. The Russians understood reliability in the field. The German fascination with precision clearances worked against them. This isn’t an internet story, one of the first people I ever worked for was named Verner Haberman, and he knew the story from personal experience in 1943.

Above, My 5th bearing running in our front yard in 2008. This is the same design that flew 450 hours on Mark Langford’s KR-2s. Just like a Lycoming thrust bearing, there is no ‘bearing’ in my design. The crank rides directly on the case material. The bore diameter is 3.375″. This makes it more susceptible to temp. growth/contraction issues, but any combination of Aluminum case, steel crank is going to face this in proportion to its size. Lycoming works with a lot of room temp clearance, but at a certain OAT, you have to pre heat the engine to prevent it from having no clearance on start up.

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To explain why testing is important, let me relate a 2009 story: At this point Mark Langford is flight testing our 5th bearing. We don’t sell things that are not tested, and Mark offered to do this work for us.  We set up the bearing housing and the crank at a very tight clearance, with a nod toward seeing if we could keep it tight after the system was at operating temps. The target was .001 to .0015″ clearance. (I chose this number, not Mark.) I had neglected to consider the lesson of Mr. Haberman. One morning when Mark had about 75 hours on the bearing he went outside to start his engine at 25F with no pre-heat. It ran for 30 seconds or so and came to a halt, locked up tight. The engine had 20w-50 oil in it, but I don’t think that was the main issue, it was the clearance. The engine had done fine through the fall, but it reached it’s limit at 25F.

OK, Why will a Corvair car with .0015″ main bearing clearance start at 25F without issue? Because the mains on the engine are 2.0″ in diameter, and my 3.375″ 5th bearing was subjected to different amount of expansion and contraction. On any Corvair flight engine, the 5th bearing is going to be the clearance issue. Roy’s bearing is 3.0″ diameter and Dan’s is 3.25″. It isn’t just the size that matters, it is the starting clearance also. Dan shoots for .0007 to .001″ clearance per inch of diameter. This is why Dan’s bearings require a High Volume pump. When they are hot, the extra clearance will drop the idling oil pressure with a stock pump. Dan didn’t make up this idea himself, he is following the bearing manufacturers specs. You could probably start Dan’s set up down to zero F without issue. 

Roy tends to run his bearing tighter than Dan’s. This is why few of Roy’s bearings need a high volume pump to maintain 20 psi as a hot idling oil pressure. The opposite side of this is that people using that design need to ask Roy about the minimum OAT for a cold start without a pre-heat.

On round two with my bearing on Mark’s plane, we polished the crank, and then rebored the bearing for .002-.0025″ clearance. This was the final number after the bearing was ceramic coated. Mark went on to fly the design 350 more hours through several seasons without issue. Again, no bearing design is immune to this, it is a consideration on all of them. You can lower the range by using thinner oil, but all the tight clearance bearings need to be preheated at some point. If you would like to read both Lycoming and Contenintal’s info on why the both require hours of pre-heat below 20F, read the articles at this link: http://www.reiffpreheat.com/Articles.htm 

These Articles discuss the relationship to the oil pressure indicating if the engine is ready to be operated. On a Contenintal, you can use full power with oil at 100F, But, the engine must not have excessive oil pressure, caused by the relief valve not being able to bypass cold oil fast enough. If you have a High volume housing and pump from us, I have machined this port larger for you. This is in the photo below, indicated by the drill bit.

Lets’ say its 35 degrees out and you start your Corvair. If your normal oil pressure regulates at 45 psi, then you will undoubtedly see the oil pressure exceed this, even with an enlarged bypass. You may see as much as 75 psi. Do not rev the engine up, let it idle. In a few minutes the engine will warm up the oil enough to bring the oil pressure down. What you are watching for is the point where you can do the run up on the aircraft and have the oil pressure regulate normally, at no more than 10psi above its normal regulated pressure. This will likely happen when the engine oil reaches 140-150F. If this takes a long time with 15w40 Rotella, you are fully invited to switch to 5W-30 Amsoil, and it will happen a lot faster. With Rotella, this may take 6-8 minutes. If this isn’t fast enough for you, let me ask what is the hurry?

The Corvairs requirements are no different from Lycoming nor Contenintal’s. Go to your FBO and tell them that you are going to rent one of their planes, but you are unwilling to warm the plane up for 10 minutes if required, because you’re a busy guy, and your time is so important. Watch how fast they slam the door in your face. They own that engine, they don’t want it damaged, and they don’t want people who disregard manufacturers instructions near them. Your Corvair is your own masterpiece, treat it at least as well as student pilots at the FBO treat the rental equipment.

 Why not get a thermostat? This will allow me to take off in 3 minutes instead of six, right? OK, for some background, go to google and search the words “Lycoming Flyer Operations” and get a look at pages 66-69. This gives a beginning description of systems that have a bypass like the Corvair and half of Lycomings, and systems that have a ‘Vernatherm’ (Lycomings term for an oil thermostat.) If anyone wants to debate that an oil bypass system allows the engine to warm up faster, realize that I have Lycoming and all their official publications on my side of the discussion. It does some of the same task as a thermostat in a simpler, smaller more reliable way.  Second, know that many Lycomings run 50 weight oil, and they need this system more than a Corvair with thinner oil. A thermostat is something that is only going to operate on your plane for the few minutes until the oil reaches 180F on a cold day. For 98 out of 100 hours a year, it is going to be open and doing nothing more than what the bypass does. Does this justify the added complexity and fittings? Should you just have the oil system set up for how it is going to run 98% of the time, with the most simple system that can accomplish this?

OK, let’s get this point fixed in everyone’s mind: They made 1.8 million Corvairs If they made on 70,000 miles each and drove this at a 35 mph average, then each car made 2,000 hours on average, which means the fleet made it to 3.6 Billion hours of operation. If only 5% of the operation was done below 32 degrees as a starting temp, I would be stunned, but lets use that as a conservative number. That means 180 Million hours of operations we done under these conditions.  Was every one of these engines carefully pre-heated? Was every start up held for 10 minutes until the oil was at 140 degrees? Was any of these hours logged with quality oil? Of course not.

The system we use on Corvairs is identical to the system used in cars. There is going to be a car guy who writes me to say that cars had thermostatic damper doors on the bottom of the car, and that they did something to regulate the speed that the car warmed up the oil. To this, I am going to point out that I firmly believe that most car owners waited less than 15 seconds after the car started to put it in gear as a habit. No system, damper doors or not, was having an effect at that point. Today the only people who own Corvair cars are people who love and respect them, and warm them up slowly. Trust me, the last guy to drive your core engine in the winter of 1979, didn’t treat it according to the owner’s manual in the glove box, and the damper doors were long since gone on your core engine. Below are some samples of stories from our webpage. The captions are the original ones with the year added in front. I put them in blue italics to show what we were speaking of at the time. The black notes are my comments today. If you still think that someone this week on the net is going to ‘discover’ something about the engines oil system I have not considered, read on and note the years.

(2007) The Corvair has an outstanding oil system. Builders are disassembling hundreds of core motors a year. These come from cars that have been sitting for many years. Most of these cars never received an oil change the last two or three years of their lives. They were continuously run low on oil and beaten like dogs. Yet just about every builder is rewarded with a crank that can be polished, or have a simple .010/.010 regrind. This is all the evidence you need to appreciate the quality of the GM design. Just like the Doctor’s Oath, your first vow is to do no harm. Many modifications that inexperienced builders propose are a serious reduction on the Corvair’s reliable oil system. Until I understood the operation of the system, I too took detours. My Pietenpol was the first Corvair to fly with a rear starter. It used a 3-hose oil system, an arrangement I now consider a mistake. Read the information here carefully, and you’ll avoid repeating missteps people have already paid for.

All Corvair engines need an oil filter, oil cooler, filter bypass and cooler bypass. The above photo shows two pencils pointing at the Corvair’s stock bypasses. The one in the rear case is the cooler bypass, and the one in the top cover is the filter bypass. They’re both set to open at 7 psi (they’re the same part). You can read all about my testing of oil accessory cases and the specific rig we built to do this on our Web site. Systems without bypasses, particularly cooler bypasses, will starve the engine for oil. Five years ago, we tested filters and coolers by packing them in ice to simulate a start at 32F. The cooler bypassed for more than 10 minutes, whereas a filter packed in ice only developed a 2 psi differential. Coolers without bypasses can cause massive restrictions in oil flow. If your pressure sending unit occurs before the cooler, you’ll have no idea that the pressure to the bearings is dropping on every start.

(2008) Above are two views of the optional Gold HP Oil Cooler Bypass. It is often referred to as a Sandwich Adapter because when installed, it’s sandwiched between the Gold Oil Filter Housing and the oil filter. It’s held in place by a very accurately machined, hollow mounting bolt. It can be installed on the Gold Oil Filter Housing in literally one minute. It includes a square o-ring gasket, held in place in a deep recess. The AN-6 fittings for the lines to and from the cooler can be clocked in any position. It contains an all metal cooler bypass featuring a precision spring manufactured by the nation’s foremost supplier of aerospace springs. On a normal start cycle, the cool oil in the cooler will produce a pressure drop in excess of 7 psi. Any time this is so, this bypass valve senses the pressure differential and allows the oil to bypass the cooler, greatly speeding up the elapsed time until the oil reaches 150F.

The drill bit is pointing to the pressure regulator bypass hole. It has to be opened up when you install a high volume pump. Otherwise the pressure will be very high until the oil temp is thoroughly warmed up. The enlarged hole allows the bypass to work with cold thick oil. Without enlarging this hole it might take 15 minutes of running on the ground on a 40 F day before the oil settled down to its normal regulated pressure. Before this, an increase in rpm will raise the oil pressure. On very cold start ups you want to watch this, because even with the hole enlarged it is possible to have the oil pressure exceed 80 pounds by carelessly revving the engine to taxi it while the oil is still cold. Give the engine a chance to warm up, don’t be in a rush. Oil pressure spikes are very rough on the drive system running the pump. This is true of almost all engines, not just Corvairs. People don’t talk about ideas like this with the buy-it-in–a-box imported engines because they just wanted to buy something and use it. Since the primary motivation with Corvair builders is to learn while creating, we talk about things. Most people are happy to just have things, people attracted to the Corvair were the ones who took apart the toaster at age 10, because for some of us, we need to know why.

Below is a series of photos of oil testing. This is on our website. It is 10 years old this month. Get a good look, no one notices this but there are beers cooling in the bucket next to the oil cooler. Testing is a tough job, but I was willing to do it.

I am bigger fan of Mich than Becks Dark. Oil cooler is in bucket. Bypass stayed open with a 7psi differential or more until the water in the bucket hit more than 130F. Beer as long gone before then. If somebody would like to differ with me on oil systems, that’s fine, but unless they have 10-year-old test photos, it’s going to be their guess vs my test.

Above, look at the instrumentation, were we have probes on both inlet and outlet lines to compare the differential. The engine in the photo is the original Skycoupe 2,700 cc power plant. Note that the stock oil filter is being cold soaked to measure the differential pressure with 32 degree oil. It was only 2 psi.

Above, the gauge pack and the digital tack on the idling engine. If you would like to read the whole report, it is on flycorvair.com, search “2003 oil system test” in the search block on the bottom of the main page. It has been there for a decade, for any one with an open mind who wants to learn. For those that like their theory more, and would like to suggest that I don’t know what I am speaking about, have a good time. When I first wrote the report, I had people say the same things at the time. In the last 10 years we have done a tremendous amount of work, helped countless builders, held 24 colleges and had many great adventures. without exception, the critics of 2003 did nothing. They are still out there, telling people what they will do some day. 2013, is no different, some people will listen to the internet critics of today and be dissuaded from doing anything this year. Decide tonight if your place will be with the builders or the critics. Decide carefully, one path leads to a flying plane and great adventures in the company of people of good people. The other leads to reading about an endless series of ‘problems’ which will be ‘discovered’ without fail by internet critics on 2 week intervals for the rest of your life.-ww

Builders,

There is a lot of small detailed information that goes into heads. But first, it is good to look at the big picture. What kind of heads do you want?  From a practical perspective, the top of the line are FalconMachine.net’s heads.  This is the product of “Mark from Falcon” or “Mark Petz” Or “M.P.” You could actually use Mark’s legal last name Petniunas. I have known Mark for about 10 years and I barely know how to spell his last name, and I know 5 ways to mispronounce it. Linguistics aside, they guy knows Corvair flight heads like no one else, he has produced well over 100 pairs of magnificent heads, and the work is beyond reproach. If you send him your cores, he will rework them, including welding on the intake pipes, for $1,270.  Theoretically you could spend more elsewhere, but you can’t find better work.

Is $1,270 a lot? Consider this: A guy with an O-200 buying 4 cylinder assemblies is going to spend about $3,800. If you add the cost of a set of 2700 cc forged pistons and rings and rebored cylinders to the cost of the heads, you end up with an apples to apples comparison of $3,800 to the Corvair’s price of $1,965.  Yes, the top half of a Corvair, built with the finest stuff, costs 52% of the same parts for an O-200. Even the top half of a 3,000 cc Corvair is only 82% of the cost of putting a top end on a Continental. (BTW, the 65 hp Continentals cost the same.)

Every time I show math like this at an Oshkosh forum, some guy will hold up his hand and say “There is an O-200 in the flymart for $5,000, and I’ll bet it is just as good as a $7,500 Corvair, and I won’t have to build it.” … Where do I start? First, if a person’s goal is to not have to build things, than what are they looking at experimental aircraft for? I like most things about O-200s except for the new owners of Continental (the communist Chinese), but the chances that the example in the flymart possesses and will demonstrate all of the qualities associated with the design are very low. Note the guy’s words carefully: “I’ll Bet”. If you are new to aviation, you might think that the man’s wager is $5,000. Heck, the guy saying this probably thinks that is what he has riding on his guess of wishful thinking. In reality, he is actually wagering far more; in escalating order of importance, the $5,000, his airframe, his safety, and his passengers’ safety. It is a lot to bet on a guess that your flymart engine has good internals.

There are two types of mindsets at work here: The flymart buyer is inherently lazy, and he doesn’t want to know what’s inside his engine. For him ignorance is bliss. On the other hand, if you are the kind of builder who wants to know what you’re doing, what you have and can count on, and where you stand, then you are always going to choose to count on your own learning and craftsmanship. You are not going to have to “bet,” you know what you have, and this is bliss to thinking people.

Above, Mark stands with his $38K Dynamometer in his shop Outside Madison WI. Note race car in background. No one should take fashion advice from this man, but is commentary on Cylinder heads is followed by many motor heads.

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The lowest cost short block with a 5th bearing we looked at in the chart was an Allen Able with 2700 cc cylinders, the AA-1 engine configuration. This cost $3,057. Add a set of Falcon heads and you are looking at $4,357. This is not a complete engine, but it is well past the halfway point and any builder getting this far already knows a lot more about aircraft engines than he did going in. The most important point: Such an engine is not made of worn parts or salvaged stuff like a flymart engine. Such an engine isn’t even how Corvairs have typically been built in years past. This is a first class engine with a 5th bearing, nitrided crank, ARP rod bolts, forged pistons, stainless valves, an excellent cam, new lifters, bearings seals and gaskets. This is something very real and high quality, produced by a set of hands and a mind that will be the master of the machine, not its servant nor victim.

The most expensive long block on the chart is the Davie Dog 3,000 cc engine, the DD-5.  Adding a set of Falcon heads to its price brings the total to $7740. That isn’t cheap, but for that price you are putting together some very fine metal. I am pretty sure no other popular alternative engine has a U.S. made crankshaft in it. Think that one over for a minute. We were the country that invented powered flight, flew the Atlantic, finished WWII with it and then went to the moon, and today, the selection of  non-certified engines at Oshkosh is almost exclusively made elsewhere. When did that become OK? Yes, virtually every VW engine sold in the past 20 years has had a Chinese crank in it. Jab, Rotax, UL, and Honda based engines are all made by people far away. I have never owned an imported car in my life, and I don’t have any desire to own an imported motor in any airplane I am building. That said, I think I can effectively demonstrate to any person with an open mind that there are very good mechanical reasons and a long proven history behind the Corvair that make it the engine of choice even for a person who didn’t care where it was made.

If you search the words “Falcon Heads” in the search box of our main page, www.Flycorvair.com, you will find many long stories describing them in detail. In the past few years there have been only small refinements in Mark’s heads. Every set now comes with the previously optional exhaust rotators,  and the final machine work on the seats is now done on ultra expensive state of the art machinery. Other than theses touches, it’s much the same. As a builder, do you have to have Falcon heads? No, but learn two lessons from others without paying for the education personally. First, I have seen a number of people drop $750 for trash work and junk valves thinking they saved $500 over Mark’s price. In some cases they just flushed $750 and had their core heads mortally wounded in the process. They didn’t save anything, they lost. Second, a great number of people who started out with local machine shop heads later converted to Falcon heads. It you are going to get there eventually, it’s less expensive to draw a straight line to the destination rather than having a several hundred dollar way point. -ww

Head group (1500)

1500- Pair of heads with seats and guides

1501- Valve spring set

1502- Retainer set for intakes and keepers

1503- Exhaust valve rotators and keepers

1504- Intake valves -6-

1505- Valve seals

1506- Exhaust valves -6-

1507- Exhaust stacks -6-

1508- Welded on intake pipes

Builders,

There is a look at the next five group topics in the new numbering system. The Head Group (1500) is the last expensive component of building a long block. The other groups here are mostly made of parts that came with your core engine and basic labor you can add yourself. Getting through groups 1000-1900 will give you an engine that is internally complete, and it is the lion’s share of the money spent building the engine

Later groups address oil systems, starters, ignitions, etc, all external systems that are bolted on your long block. All of this can be purchased as you go, adjusted on your own timeline and budget.  The later parts are intentionally broken down into affordable blocks that can be installed at one time, like the $516 starter system group (2400).

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Head group (1500)

1500- Pair of heads with seats and guides

1501- Valve spring set

1502- Retainer set for intakes and keepers

1503- Exhaust valve rotators and keepers

1504- Intake valves -6-

1505- Valve seals

1506- Exhaust valves -6-

1507- Exhaust stacks -6-

1508- Welded on intake pipes

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Valve train group (1600)

1600- Pushrods  -12-

1601- Pushrod tubes  -12-

1602- Pushrod O-rings  -24-

1603- Rocker arm set  -12-

1604- Rocker balls  -12-

1605- Nuts  -12-

1606- Lock nuts  -12-

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Head clamping hardware (1700)

1700- Guide plates -6-

1701- Stud O-rings -12-

1702- Rocker studs -12-

1703- Upper head nuts -12-

1704- Upper head washers -12-

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Steel engine cooling baffles (1800)

1800- Under cylinder cooling baffles -2-

1801- Clips to retain engine cooling baffles -4-

1802- Baffle between #1 cylinder and distributor

1803- Baffle between #2 cylinder and oil cooler

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Valve Cover Group (1900)

1900- Valve covers -1 pair-

1901- Hold down clamps -8-

1902- Hold down hardware 1/4″-20 -8-

1903- Valve cover gaskets -2-

1904- Oil fill cap

Builders.

Phil Maxson sent in the following chart so we can look at the different approaches outlined in Part #16.

Later tonight I am going to go over some Mail Sack questions and comments on this series, Any builder with input can send it in this afternoon and we will cover it later tonight.-ww

Builders:

The last option I want to look at in the piston department is our 3,000 cc stuff. These are basically 92mm versions of the 2,850 cc kits. This bore requires the case and the heads to have machine work done to them. This work is included in the price of $2,200 for the piston/rings/rod/cylinder kit. Last year I wrote a fairly detailed description of the 3,000 cc engine choice at this link:

3,000cc Case Modifications.

3,000 cc engines have been very popular with Corvair builders, but they are significantly more expensive than other Corvairs. As I pointed out in the last part, this increased expense seems small to a guy who was  looking at a Jab 3300 or a Rotax 912. People who had previously felt restricted to expensive imported engines find even the top dollar Corvairs very affordable by comparison.

For this part I am going to skip the individual part listings for the 1300 and 1400 groups as they apply to the 3,000 cc kits, builders following the series grasp that we sell the 3,000 kits just like the 2,850’s but the 3,000cc kits require machine work to the case, work we are glad to do and is included in the price.

Looking ahead, let us imaging a chart with the 5 case options listed below , AA through EE, on one axis, and the 5 piston/cylinder choices on the other. This chart will outline 25 different engine build options. Does this begin to illustrate the flexibility of Corvair building to suit individual builders needs and budgets? Technically, the 2,775 cc option in column #3 doesn’t yet exist so it is really just 20 main options. But even from here there are variations and sub options.

No one should tax their imagination very hard to picture the chart because I have 601 builder/flyer Phil Maxson working on it for Part #17 right now. Once we have this in front of us I can demonstrate the power of the new numbering system to quickly and accurately describe individual Corvair engines, and builders will have a very good idea of what it will cost to produce their own version.

Here is an example: Dan’s Panther prototype engine,

Panther Engine Is Alive … ALIVE 

can be called a DD-5 short block. Greg Crouchley’s engine,

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Engine options with 5th bearings:

Allan Able = $2,062

(See part #5)

Bob Baker = $2,516

(See part #6)

Chas, Charlie = $2,770

(See part #7)

Davie Dog = $4,270

(See part #8)

Eddie Easy = $3,157

(See part #9)

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1)…2,700 cc, Sealed power pistons/rebored stock cylinders = $995

(See part #13)

2)…2,700 cc, Sealed power pistons/ new clarks cylinders = $1,295

(approx. price)

3)…..2,775 cc Forged Dish pistons/ rebored stock cylinders = $1,377

(See part #15)

4)…..2,850 cc Forged Dish pistons/ new clarks cylinders = $1,750

(See part #14)

5)….3,000 cc Forged Dish pistons/ new cylinders/ machine work to heads and cases = $2,200.

(See part #16)

Builders.

The next piston option we are going to look at is one that doesn’t yet exist. That may sound funny, but it will give builders a look at how new options come about, and how we work to make parts that really serve builders needs and make sure they are carefully introduced.

If you do the math. a .060″ overbore (in motorhead jargon this is called “Sixty over”) on a Corvair produces an engine that is 2,775 cc. Pistons already exist in this displacement and we have built plenty of engines for aircraft using them. What is different? The piston I am proposing here is a baby brother to the 2,850 see in part #14. The primary difference is that the 2,850 requires the new Clark’s cylinders to get the .105″ overbore. the 2,775 cc would bring the advanced combustion shape to Corvair flight engines using stock core cylinders. We have actually been looking at details on this design for two and a half years.

In the last post I pointed out that the flat top pistons have a long service history in Corvair flight engines, but it isn’t the perfected design to compliment the combustion chamber in flight engines. If you don’t have a clear picture of the advantages, review part #14.

Just so every one stays on the same page, I am going to always call the flat top forged piston engine a “Sixty over” engine, and just refer to our dished piston engine as a “2,775 cc engine” even though they have the same displacement.

Any piston we would make would sell, however, I don’t base my decision to make products because they will sell, I base it on if they are a real definite improvement over what already exists and can be flight proven to be so. We flew this displacement as the initial engine size in our 601XL in 2004. There are advantages for people who choose to be able to run auto fuel with these pistons.

Who would go after building one of these 2,775’s? Good question. I visualize it as a maximum upgrade on a guy’s engine who is building on a very tight budget. The potential cost savings over a 2,850 is at best $400-$445, not a giant difference, but not pennies either. The engine would end up being 2 or 3 pounds lighter than a 2,850, but that isn’t a big issue.

The main issue is that we have builders approaching the Corvair build from two different angles: Often guys who are looking at 2,850s and 3,000s originally were looking at very expensive engines like Jab 3300s or a 912. To these guys, any Corvair is comparatively low-cost, and an extra $445 isn’t going to change that perspective one bit.

On the other hand, we have plenty of builders who are very carefully budgeting their engine because they were first looking at buying a ‘flymart’ A-65 for their Pietenpol or an O-200 without logs for their 601. They choose a Corvair because they know that it is far better to trust their own engine building and parts selection rather than relying on the naive belief that the inside of a uninspected engine “should be alright.” For these guys, $445 matters. If we can show these guys that there is a path for them to have the same advanced combustion characteristics in a slightly smaller displacement, then we are staying true to out goal of keeping the engine affordable and keeping our R&D in a position where it benefits most builders, not just the ones building engines on looser budget.

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Piston and rod group (1300)

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1300- Piston set with wrist pins

Our piston sets come with their own pins. Pistons would be set to use either standard Corvair rods or ones bushed for floating wrist pins.

1301- Ring set

1302- Connecting rods -6-

The rods here are standard rebuilt ones with ARP bolts.  Clarks 9203ww rods end up costing the builder $261 after he sends in his cores.

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Cylinder group (1400)

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1400- Cylinders -6-

The Cylinders for a 2,775 cc engine would be rebored ones from your core engine. Again, Clark’s is your best bet, they have bored at least 20 sets of stock cylinders to .060″ for us over the years. After you mail in your cores, the final price on the exchange cylinders is about $150.

1401- Base gaskets -6-

The base gasket that I prefer for all Corvair engines is the all copper Clark’s part number C-1180. As a part number for an individual gasket, you will need to order six of them for a complete engine. We install them in the engines dry, with nothing on them. We built engines for many years with the stock steel gaskets, but they are less forgiving than copper base gaskets. A set of six is about $42.

1402- Head gasket set

For 1965 headed engines, the standard head gasket that we recommend is a .032” solid copper gasket. These are available from Clark’s, part number C-3946 The head gasket set is about $30.

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The proposed total for the 2,775 cc Piston/rod cylinder combo is $1,505. We sell the 2,850 kit for $1,950.

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 That is a reasonable price to pay for a better piston that is designed from the very start to run on reasonable quality unleaded car gas without complaint nor re-tuning.  The nominal HP rating of the engine would be 105 hp continuous.  If it appeals to you, by all means, drop me a note and say so. But for now, let it just be a proposed place holder between standard and increased displacement engines.-ww

Above, a 2,850 piston made in the USA, specifically designed for flight engines. The proposed “2,775 cc” would look identical, but be .045″ less in diameter and have a different chamber volume.