Getting Started in 2013, Part #12, Piston Choices


Here is a look at some notes on the 1300 group. I left out the 1302 section on rods because I am revising it now. For right now this is a good overview on piston choices.

Engine kit notes:

Builders purchasing a 2,850 or 3,000 cc large bore kit from us receive the new forged pistons, the wrist pins, Total Seal piston rings, new cylinders, head gaskets (2,850s get base gaskets also, 3,000 cc engines don’t use them), and professionally rebuilt connecting rods with ARP rod bolts with 12 point nuts. The price of the 3,000 cc kit includes the machine work to the case and heads to accept the larger bores. Builders selecting either of these options will be fulfilling the contents of both the Piston and rod group (1300) and the Cylinder group (1400).


Piston and rod group (1300)

1300- Piston set with wrist pins

1301- Ring set

1302- Connecting rods  -6-



In January of 2011, when I still was a part of online discussion groups, I sat down over four nights and wrote the history of pistons and cylinders on Corvair flight engines. It included the who, what, where, when and why of the whole spectrum of possibilities. It was a four-part story that covered nearly 18,000 words. I looked at it before writing this section of the Manual. Reading it now makes me reconsider things. The life of a great person is worthy of such documentation, but is the history of pistons and cylinders on Corvairs a valid subject at this length? Who was I writing it for? Was it to convince skeptics that I really am “The Corvair Authority”? The people who are focused on the Internet discussion liked it, but I doubt it needed that length for people focused on building. I am writing this for people who want to know how to build an engine today, to use it to fly, and a much shorter piece is afforded by this focus. I am just going to cover the pistons we use today, have a short section on what not to use. Please realize that there is no combination that you are likely to hear of that we don’t know about. We probably test ran it, and may have flown it. If it isn’t in here, there is a reason. If you ignore that reason, the odds of your plane ever getting finished just got smaller.

1300- Piston set with wrist pins

There are three displacements of Corvairs that we build today. They are the 2,700 cc series, the 2,850 cc and the 3,000 cc engines. There are two good piston options for the 2700 and they both come in 3.437” standard bore, .020”, .030”, .040” and .060”. The pistons for the 2,850 and 3,000 cc are available from us; they come as part of Piston/ring /cylinder kits, but we will discuss them as a separate part here.

First, a quick mention of all the pistons you should never use in a flight motor: Never use a cast piston of any kind. This includes old GM pistons, the ones sold by Clark’s as “high-tech,” any piston that is labeled as Hypereutectic, and the vast majority of pistons intended for VW applications. All of these cast pistons have flown in Corvairs before, but we have been telling people for 20 years never to fly any kind of cast piston because they are not tolerant of any kind of mistake in engine assembly, tuning nor operation. Their life span in an engine that is detonating hard is about 15 seconds. This will also hurt forged pistons, but they will not break or get holes in the piston tops. The second type of piston never to fly is a forged one made by a company focused on making light weight, high rpm pistons with thin tops. Pistons designed to make the most power at 7,500 RPM are different from ones designed to be ultra-reliable in 4,000 RPM engines.

Traditionally, the most popular Corvair flight piston for a 2,700 cc engine was referred to as the “TRW” piston.  In the past 10 years, a corporate name change on the box led most people to call these “Sealed Power” pistons. Until 2009, these were made in the United States and the quality was very good. About eight years ago, the pistons began coming with a greenish gray anti-scuff coating on the skirts. Approximately 90% of the Corvairs now flying have these pistons in their bores. They were available in standard, .020, .030, .040, and .060. Over the years, I have built more than 100 engines using these pistons, almost all of them .030 and .060. They work very well in flight engines and have an excellent reputation for staying together even in engines that are being detonated heavily. I have never seen a hole punched in the top of one of them.

In 2009 the wonderful world of outsourcing had the manufacturing of these pistons moved to India. The corporate ownership was so proud of this change that they announced it by keeping the box exactly like it was with the sole exception of printing the words “Made in India” on the end of the box in a print size usually reserved for credit card contracts. The pistons manufactured in India look exactly like their U.S. counterparts. There is nothing wrong with them; however there is clear, irrefutable documentation that the manufacturing tolerances of the Indian built pistons are significantly looser than their U.S. built predecessors. I would not seriously worry about this, but it is a reality. These pistons are available from many different sources, including Clark’s.  

1301- Ring set

The kits we sell for the 2,850 and 3,000 cc engines include Total Seal rings. These rings are carefully matched to the bore finish of the cylinders that come with the kits. These rings feature the highest quality chrome steel, from a company known for a quality product. The brand it Total seal, which people thing is ‘gapless’ which is not so. Total seal bakes both gapped and gapless rings, we use the former.

For builders working on a 2,700 cc engine, there are numerous choices when it comes to rings. Over the years we have tried them all. I feel that the best combination for a Corvair flight engine is the Hastings chrome ring mated to a 220 wall finish on the cylinder. There are also moly rings available for the Corvair, and the appropriate finish for these rings is 280. We have built a number of motors around moly rings but I don’t see any particular advantage in our application.  With proper break-in, regular oil changes, and breathing filtered air, the lifespan of chrome rings should easily be 1,500 hours. Moly rings would theoretically last longer, but they are far more difficult to break in and they are less forgiving of the wall finish. We have also flown a number of engines on regular cast iron rings. These break-in literally in minutes and they are surprisingly tough. Their Achilles’ heel is any kind of detonation. Even a few moments of knocking will often crack a top ring if it is only made of cast iron. Although their low price makes them tempting, stick with chrome rings.

The rings that go in your engine must be the same size as the pistons. For example, .030” over bore pistons require a .030” over ring set. Corvair piston rings are expensive by automotive standards. If you shop around you can often save a significant amount of money.


Calling Central FL builders, Meeting 9am Sat. 26th


Just a quick reminder that I am going to be the guest speaker at the Leesburg EAA chapter at 9am. The meeting is held at the airport in the hangar on the west end. I am headed down to meet the members of #535 and answer any remaining questions they may have about the up coming College #25 at Leesburg. If any builders are in the area, feel free to stop by. I will be there until 12 noon.-ww

Mail Sack, 1/25/13. Terry Hand Editorial, Numbering System


Here is a sample of the mail on Terry Hand’s Editorial:

Zenith 601XL builder and flyer Phil Maxson writes:

“This is an excellent article. Each of these points resonated with me, but I’m particularly struck by number 5. I am beginning my 24th year with Mars, Inc, a mult-national food company. We are very big on the Freedom principle, and in our case, it is called “Freedom within a framework.” In a company of 70,000 associates it is not possible for everyone to have their own “do whatever you like” form of freedom, but each one of us is obligated to exercise our own talents and skills within our purview. We have a framework that includes five principles: Quality, Responsibility, Mutuality, Efficiency and the one I’m emphasizing here: Freedom.”

Builder Matt Lockwood writes:

“Terry- Thanks for this. Especially point #1. There is a certain discipline that comes with making yourself slow down and consider the ramifications of your decisions…i.e fish tank tubing for fuel lines and/or routing it through the cockpit. Some of the information that is out there on the internet doesn’t consider the ramifications, nor do these anonymous advisors out there have to suffer the consequences of you taking their advice. Everyone, please be careful. Thanks again to you and to WW. P.S. I thought ‘NATOPS’ stood for ‘Navy’s Attempt To Operate Planes Safely’Matt Lockwood, VT-3 1997-1998”

Builder Jerry Mcferron writes:

“Footnotes and warnings are often written in blood. Don’t add yours.”

“In the early 60s my Dad was a Navy flight instructor at Pensacola teaching in T-34s. Earlier, in 1958, Dad was the co-pilot in a helicopter that crashed and he was severely burned. He was the only survivor of the four crew members. A few years ago I received an e-mail from a lady looking for my Dad. Her Dad was the pilot of the helicopter. She had not yet been born at the time of the crash, so she had never known her Dad. If the fates of our fathers had been reversed, I would not be here. The investigation into the crash resulted in changes to the procedures for flying helicopters. Dad is now 76 and passed his physical a few weeks ago. He is still teaching people how to fly. When Dad calls me and says “I got to go flying today”, it makes my day.-Jerry”

Builder Dan Branstrom:

“Amen, and Semper Fi.”

On the topic of the numbering system, Builder Harold Bickford writes:

“Hi William, It is quite clear that as long as a supply of heads and crankcases are available the Corvair conversion will continue unabated at an advantageous price. Even new cast heads and crankcases would not be impossible if the need arose. Given that aftermarket new cast Chevy 409s are available at around $5,000 suggests cost-effective supply would not be an issue.The key is to build it here.-Harold”

On the topic of the numbering system, 750 Builder Blaine Schwartz

“William, This is a great explanation of how the Gold parts assemble and the reason why there are the way they are. Sometimes, we builders read instructions and then either forget them or hear some BS regarding a better way. I have all your Gold parts and have most of them either installed (engine components) or am in the middle of installing them and this reminder you posted is invaluable to help keep me on track. Those small comment like the bushing for the PM generator will save me a lot of time! I continue to be amazed why a builder would literally put their life in the hands of an unknown “internet voice” rather than following proven methods. Keep ‘em coming! Thanks, Blaine”

Guest Editorial, Pietenpol builder Terry Hand.


Tonight’s Guest editorial is from Pietenpol builder Terry Hand. Terry was motivated to write this by attending several Corvair events and watching many of the builders present share their expertise with other builders. Previously I have written about different entry points into experimental aviation. Terry is arriving from a long professional background of a USMC/ATP experience. As he relates, some of this directly applies to experimental building and flying, and some does not. In a story last week I commented on arrivals from other branches of aviation already understanding the ‘rules.’ The following piece is Terry’s contribution to his fellow builders, bringing some perspectives from his other lives in aviation.

Like our other editorials, I encourage builders to cover their thoughts in 2 or 3 thousand words. In most communication places on the web, this would be a titanically long piece. However, I am not running this site so that we see how brief exchanges can be. important topics should be covered in more than bumper sticker  slogan depth. This is not the trend in our industry. For 10 years there has been a move toward the 400 word story. Even EAA publications had an in-house memo stating that they would never publish a story that was 1,500 words again, even on-line. This was a concession to data that showed the new marketing target was a generation of people bred by tv and the internet to have very short attention spans, and they “didn’t like reading about concepts nor details.” Does that sound like the kind of people we need more of in flying? Have no worries, people like that don’t get far in flying and they are easy to steer clear of.

In the Corvair movement we are blessed to have many thinking people with long diverse experience to share. I will confess to shamelessly welcoming people who are inclined to learn, think and consider. Most of my waking hours are spent on the subject of aviation, there is no reward, monetary or otherwise that would make me want to share those hours with people who blindly wandered though aviation, treating it as another consumer experience, unaware of, or not interested in any of the things that go into becoming a better aviator. Send those people to the shopping malls, airports are for people who are alive and awake.-ww

.Above, Terry Hand with his steel tube Pietenpol at CC#24


 “Common Logic and Philosophy in Aviation”


It may be useful to introduce myself and my background in aviation at the beginning so that anyone reading this can see the path I have traveled in my flying. I began my flying career where thousands of pilots have done both before and after me – NAS Whiting Field, Florida, and Navy Flight School. I was in the better part of Naval Aviation – Marine Aviation! I went through fixed wing Primary Flight Training followed by Advanced Helicopter Training. I went to my first squadron as a UH-1N (Huey) pilot in Hawaii for 3 years and flew off of Helicopter Assault Ships in the Western Pacific for 14 months. I followed that tour by eventually returning to Pensacola as an instructor in Primary Flight Training, instructing in T-34C’s. I left the Marine Corps and went to work for a major airline and worked my way through my career as an engineer on 727’s and L1011’s, and First Officer and Captain on 727’s, 737’s 757’s 767’s and MD-88’s. During my career at my airline I spent almost five years as an instructor in 757’s and 767’s. I currently fly as a Captain on 757’s and 767’s both domestically and internationally. I am a CFI and CFII, and have instructed in everything from Cessna 172’s to Boeing 767’s. SO what does all of that mean? It means I have seen good principles, and bad principles, good decisions and bad decisions in aviation, and I have seen the positive and negative results. I have seen near misses, and I have squadron mates that I will never see again that were killed over the Pacific due to bad decisions. So here are a few principles that I have learned over the years in my flying career that I think carry over into the construction of my aircraft of choice (a steel-tube fuselage Pietenpol), and my engine of choice (a 2700cc “Bob Baker” Corvair). In no particular order-



  1. When planning and decision making, always plan for the worst to occur. If bad things don’t happen – you sleep well at night. If bad things do happen – you were ready. Let me give you an example. When I flew helicopters, I learned very early on not to fly from Point A to Point B. Rather, I learned to fly from Point A to a farmer’s field (one I could autorotate to and land on in the event of a catastrophic failure of some kind) to another field, to a parking lot, to a football field, and then to another field, on my way to Point B. It was the philosophy that, if a catastrophic failure occurred, I had choices and had a good chance of surviving. How does this apply to building my airplane? If the plans call for aviation quality plywood for building gussets, and you find a good price on some plywood at the local big-box store, stop building and go get the right material. Do not assume that it is probably okay to use that plywood.Plan for the worst. In another example, that is why I won’t route any fuel lines through the cockpit area and I won’t use plastic fish tank tubing for my fuel system. If I spend a few extra bucks and buy quality fuel line materials and fittings and never make an off-field landing – I sleep well at night. If It does happen, and my gear collapses, or the aircraft suddenly comes to a crashing halt – I am much more likely to avoid fuel leaking and causing a catastrophic fire.

  2. Skills may be similar, but they are not always equal. In my commercial aviation career I have flown everything from the 737-200 to the large 767-400ER. In the course of my career I flew for several years as a co-pilot on the Boeing 727. What a great airplane! We use to jokingly say that you could probably hit the Outer Marker on an ILS approach at 250 knots and still be able to slow down and configure the airplane for landing by the time you got to the runway. I am not sure it was a true statement, but it wasn’t far off. Pull the power off, and man could that airplane slow down! Contrast that with the 757/767 series of aircraft that are extremely clean aerodynamically. Especially the updated 757‘s with winglets. We often tell the controllers when they request a steep descent along with a speed reduction, “I can slow down, or I can go down, but I can’t do both.” If you tried to fly the 757 in the same manner as you flew the 727, you would always be high and fast on approaches. Yes, they are both airplanes (and Boeing products at that), but the skills required to fly them are different. The same is true with skills we bring to building our aircraft. You may be a gear head from your teenage years (I certainly wish I was), but the ability to tear down a rebuild an auto engine is nowhere near equal to building a Corvair. To equate the two and the knowledge and decision-making required is to run the risk of hurting yourself or someone else by building an engine that may be roadworthy, but not airworthy. The skills may be similar but not equal.

  3. Listen to experience, and don’t try to blaze new trails. Trust me, you are not the first guy to come up with that idea. When I was an instructor in Pensacola, we taught from an extremely standardized syllabus, one that allowed us to evaluate all students against a known training standard. Every once in a while a new instructor would arrive, and he just KNEW that his way of teaching a skidded turn stall recovery or an emergency landing was just a little bit better than “the Navy way.” While it was admirable that he wanted to improve the syllabus, usually his way was a way that had been studied, evaluated, and found to not work as well as the approved method. And usually his way didn’t teach the student as well as the approved method and the students training actually suffered as a result. So how does that apply to building an airplane? Are you using AC 43.13 as your road map of acceptable construction methods? Or have you decided that it only applies to certificated aircraft, and you don’t need it. In reading The Corvair Manual, do you find things that you are doing to be at odds with what the manual has told you is the tried and tested method of doing things? Blazing a new trail usually isn’t new, and don’t be surprised if you get stuck by some thorns while blazing that “new” trail.

  4. Footnotes and warnings are often written in blood. Don’t add yours. In the world of Naval Aviation, our POH was referred to as ‘“the NATOPS Manual” (short for Naval Aviation Training and Operations Procedures Standardization, a real mouth full, so NATOPS was just easier to say). All through the NATOPS manual were highlighted cautions, warnings and footnotes. When I was a student, I had an Instructor in Pensacola teach me early on when he said, “Read and heed those warnings. Most of them are written in blood.” What he meant was most of those warnings were added after some pilot had done something wrong in operating the aircraft that either damaged the aircraft, injured or killed someone, or had done both. How does this apply to our discussion? I look at my Corvair Manual as the “NATOPS manual” of building and maintaining my engine. If it tells me not to do something, there is most likely a story behind that warning. Maybe it is the story of an engine being built incorrectly and causing undue expense or delays in the building process, or worse, damage to the aircraft or pilot.

  5. Standardization does not inhibit freedom. It enhances it safety. I have spent the lion’s share of my flying career in jobs with numbers of checklists and standardized procedures. I used to think that checklists were sometimes excessive and prevented me from “being an individual” (whatever that means). Real men don’t need checklists, do they? I felt that they made me just a robot pilot like all other robot pilots. Then I came to this revelation when I was a 767 instructor many years into my flying career. The purpose of checklists was not to make you a robot or take away your freedom. Rather, it was to identify the big stuff – the stuff that would kill you. The checklist helped you to take care of those items, then gave you the freedom to fly within those boundaries set by the checklists. Think of it this way in your own flying. Look at the checklist you use in flying any airplane. Read the checklist and leave an item out and ask yourself, “If this step was not part of the checklist and I forgot to do it, what is the worst thing that could happen?” Refer back to Point 1 above. So how does this apply to building? Again, I refer to the instruction provided by the Corvair Manual, fly and Those documents and writings may not be formal checklists of how to build and maintain your engine, but they are pretty darn close. Use those checklists to avoid that things that can hurt you, thus leaving you the freedom to build your engine your way in the areas left to your discretion.

  6. Practice, Practice, Practice. I have been in a training environment for a large portion of my flying career. I can remember as a student in Pensacola spending time in cockpit procedures trainers (non-moving simulators) as well as full motion simulators practicing my checklists, start procedures, maneuvers, and emergency procedures long before I ever set foot in an airplane. The practice made my flying better, and the end product (me, as a pilot) was better than if I had just tried to learn as I went along. That training has continued through today. I go in a simulator twice a year to practice procedures. What does that have to do with building? As an example, if you are a non-welder (like me), don’t let your first welds be your landing gear! Practice welding, or gluing wing ribs, or making connectors for your electrical system, or any of a host of other skills necessary in building your airplane until you are satisfied with the quality of the work before you ever do the same work on your actual airplane. Don’t be in a hurry to build. Many times people jump into a new phase of construction and try and learn “on the fly” (no pun intended). Aviation will kill you if your work is not quality work. Look at every joint, every weld, and every part of construction as if your life depended on it, because it does.


I hope that some of these principles may cause you to think, or even rethink the way that you are planning or building your aircraft. I am sure someone (or maybe many people) are thinking, “What is this guy talking about? This is not military aviation or commercial aviation, or even general aviation. This is experimental aviation. I can do as I see fit.” Did you notice the same one word used four times? Aviation. It is all aviation, and the same principles carry across all of aviation (refer to the quote at the beginning of this writing). These principles can help you or hurt you, depending on how you respond.


Semper Fidelis, Terry Hand

Running an Engine at a College, required items. #2


This letter came in from Pietenpol builder John Francis:

“William, I attended CC #20 and was happy to have my case checked out by Roy and get it assembled. I am slowly gathering the parts I need to complete the engine. What engine components are necessary to have my engine running at a Corvair College? Or, perhaps it would be easier to list those I don’t need ie carb, alternator, prop, etc? Perhaps as you publish the numbered groups you could put an asterisk by those that are needed to get an engine running at a CC college.”

Above 49 of the 70 Corvair builders at CC#20 in Hillsdale MI June 2011.

John, Thanks for your note. Looking at the photo of the builders at CC#20 brought back a lot of memories and made me think of all the things we will get done at Colleges this year.

Corvair College #20 

John has a very good on line builders log with lots of pictures of his project. I borrowed this one of John at CC#20 from his site at :

 Fifth Bearing installed on engine 

I borrowed this one also, it shows Johns ‘closed case’ with an original Dan Gen 1 bearing installed. This is one of Dan’s original housings, the first 120 or so were heat-treated castings. Today they are made from CNC billets of  6061. Dan made the switch to take out a lot of the different steps in the manufacturing process like working with a foundry and heat treater.  They cost more to make as a billet, but he kept the same price to builders.

Above, Spenser Gould, designer and Builder of the SP-500, with his first engine run at CC#23 in Palatka Florida, June 2012.

…..You are correct, it is easier to list the things that live on our run stand that a builder doesn’t need to bring. Looking at the above photo from#23 for reference, the test stand comes with:

Full exhaust system.

intake and carb and throttle connections, and hardware.

its own self-contained fuel system.

All the ignition components except the distributor.

It has its own bushings and mounting hardware.

the stand uses the cooling baffle on all the test runs.

Propeller and mounting hardware.


To run, engines don’t need a charging system. However, you will see a lot of them running in pictures with the Front alternator bracket (2900) in place, because the inboard bracket for this item fits behind the ring gear, and it is much easier to mount it before the ring gear and hub are on.

The only part of the ignition you need is an E/P distributor or a dual points one.

The intake on the stand is designed to mate with welded on head pipes that match the pattern I developed in 2004. I also have a set of adaptor pipes that mate the stands intake to stock Corvair heads, but this takes a bit of time, and I often try to run these engines last at the Colleges. If a builder is using his own custom intake pipes on the heads, he needs to make a set of pipes that will mate to his heads and to our intake. I will put in a good try to run such engines, but they go last and we don’t guarantee that we can do it. We have succeeded in about 4 out of 5 tries in past colleges.

Virtually all engines run at the last few colleges had Gold oil systems. One or two had stock GM ones. If you have an old remote oil filter system, you need to bring your own filer, housing and hoses. Six or seven  years ago the run stand had these items mounted on it, but they are no longer there. If you have questions on this call or write. I would like to run a lot of engines at Colleges this year, it is a very big mile stone in a builders progress that is always a special event.-ww

Mail Sack, 1/23/13, “the rules”


A sample of the mail on the topic of “the Rules”

Zenith Builder/flyer Andy Elliott ( )writes:

“I liked very much this particular part of your last posting, and am working on a rewording for posterity. Please review and provide editorial comment if you like, since it’s going to be attributed to you, unless you tell me otherwise! Airfield Entry Sign:

“WARNING: You are now leaving the regular world, where score is not kept and it is always someone else’s or society’s fault. Here, score is kept, by the impartial judges of Gravity, Physics, Chemistry and Weather. Regardless of your good intentions, civil laws, or religious beliefs, here the death penalty is in effect. It is still considered cruel here, but it is not that unusual. Outside you may be important or protected, but here you will only find security and success by your own efforts to learn and abide by The Rules. You are now on the property; the game is in play.”

Andy, I actually like your version better. It would be nice to see it posted at an airport to see if anyone got it.-ww

Texas Builder Dan Haynes ( ) writes:

“hmmm, an ex -38 driver building a Corvair powered Midget Mustang…..sounds eerily familiar. Have your agent contact my agent. We should talk.”

3,000cc Waiex builder Greg Crouchley writes:

“Amen. And thanks for continually striving to point this out. The life you save next might be mine. Best regards, Greg”

Front and Rear alternators, their part in numbering system


I am going to jump ahead in the numbering system to alternator choices. As you will see, The standard charging system, the front alternator system we have used for 9 years is Standard charging system group (2900).  This is the system that we sell on our website at the link below. It is the working system on about 150 aircraft.

Above, the Hangar Gang Wagabond in it original configuration that it had from 2005-2012. This is made of early parts and has a black hub and a modified alternator pulley. This system evolved to a much cleaner configuration when the Gold hub came in 2006. The photo also shows an early FRA-235 ring gear that has been superseded by a solid model. The Alternator is used with its stock pulley on a Gold hub system. The photo is a good representation of how the current systems evolved over time and have long been flight proven.


In the last year I worked with Dan Weseman to develop a direct drive rear alternator set up for the engine. Dan was looking for a system that he could use as a very compact arrangement for his new Panther aircraft. After much development, Dan took the lead on the project and worked out the details and manufacturing on it. I wrote it into the numbering system as Rear charging system group (2950). Although it is ground tested, Dan wants to hold off sending any out until we have it on an in-house test bed aircraft, either the Wagabond or his Panther. The target date for having them available pending flight tests is Sun n Fun. Dan and Rachel have had some notes on the rear system on their website, linked below. When the system is up and tested, it will be available from them as an alternative to our front system. More updates will be on their site as it develops.

Above is a high thrust line Pietenpol mount bolted on a Corvair with our standard intake an MA3 carb and the prototype rear alternator. All of our components are integrated to work together on this. The rear alternator makes its amperage output at a higher engine rpm because it doesn’t have the ratio advantage of the pulley. In ground tests, the rear set made good output, plenty for most simple aircraft. For single seat or tandem seated aircraft, a sleeker cowl may be possible. On side by side aircraft like the Zeniths and the Cleanexes, the front system fits inside the cowl nicely.


One of the first questions builders ask about the rear system is if we think it will allow more cooling air into the cowling. This is to be determined, but I don’t think that the front system is a choke point like some people eyeball it to be. Further down the road we can have some type of before and after test on the same airframe, but for now I would like to have people interested in cooling to review the four articles I wrote on the topic here last year. The links are below:

Corvair Cooling, Three 2007 examples from our hangar.

Corvair Cooling, something of a human issue…..

Corvair Cooling

Engine Cooling Factory Sheet Metal


Getting back to the numbering system, Below are how the two groups are laid out in my system. After both outlines, I give an example of my full notebook entry on the 2900 group, not just its outline form. It is lengthy, too long for the overview we are working on here, but I wanted to show builders the full depth of the information on this one topic. After this I am going to go back to the Rod and Piston group (1300) and the Cylinder group (1400). The full set of notes on those two groups is about 7,000 words. A lot of detail, but too long for keeping people focused on the big picture. I want builders to see enough to picture which engine they want to build in 2013. After that decision, we can go back and look at any component in the kind of detail seen below.


Standard charging system group (2900)

2900- Front alternator bracket

2901- Mounting hardware

2902- Permanent magnet alternator

2903- Altermator mounting hardware

2904- Drive belt

NOTE: If you opt for group 2900, then delete group 2950.


Rear charging system group (2950)

2950- Rear alternator bracket

2951- Mounting hardware

2952- Permanent magnet alternator

2953- Alternator mounting hardware

2954- Drive coupling

NOTE: If you opt for group 2950, then delete group 2900.


Below is a sample of the full write up on the 2900 group from the build note book, -ww


Standard charging system group (2900)



The standard charging system that we utilize on Corvair flight engines mounts a 20 amp belt drive alternator on the front of the engine. The system has a perfect reliability record while meeting the needs of Corvair builders in an economical manner that does not compromise any other system on the engine.

Over the years I have used many different charging systems on flight engines we have built. These include the stock Corvair alternators on blower fan engines on Pietenpols, one wire alternators, 60 amp teacup ND alternators, and several different models of the current AC dynamo mounted in several different places on the engine. The designs we recommend are based on this experience. Many people jump to the incorrect conclusion that we recommend 20 amp alternators because I have not tried more powerful ones or explored other ideas. A quick look at our Web page will show several Zeniths we built engines for in 2009 with 60 amp alternators.

The first question that most builders have is whether or not 20 amps is enough output for their aircraft. The most common mistake builders make when adding up the electrical power usage of their aircraft is assuming that they are going to be utilizing all systems at once. This would make the assumption that all of the loads would be full-time rather than intermittent. Looking at the most basic version of this concept, cranking the starter pulls about 250 amps. Does this mean that you need a 250 amp charging system? Of course not because cranking the starter is an intermittent load, and the reserve energy for it is stored in the battery. On a smaller scale, transmitting on the radio is the same concept. To an extent, operating a landing light is the same idea. Any time the electrical system demands are briefly higher than the output of the charging system, the battery is there to make up for the excess demand.

We frequently have builders tell us that they’re going to put a glass cockpit in their airplane, and they erroneously feel that they would need a much larger alternator to run this. In reality, glass cockpits use almost no energy as they are modern electronics and they run with significantly lower power consumption requirements than other types of instrumentation. The same goes for modern LED strobes and lighting, which consume a tiny fraction of the power required by traditional systems. Even modern radios transmit much more efficiently. Any realistic analysis of the power requirements of 99% of Corvair powered airplanes will show that they can run on 20 amps or less. To have a larger charging system is to be carrying excess weight on every flight. New builders are often attracted to unproven or unreliable modifications to the engine in order to reduce its weight. The same green builders will often be interested in charging systems that weigh more than double the 20 amp system that we use. In time, these builders will learn by studying successful installations to prize proven reliability above all else and learn why aircraft have charging systems sized as they are.

There is a second temptation among new builders to want to see the alternator moved to the rear of the engine because they imagine that it somehow interferes with cooling. The best proof that it does not are the dozens of airplanes flying with it up front. The Wicked Cleanex flew hard aerobatics at wide open throttle on a 120 hp Corvair, as you can see on our Corvair Flyer #1 DVD. It never overheated, and of course, its alternator is up front. There’s a serious liability to having a belt driven alternator on the back of the engine. The Corvair’s ignition system is on the back of the engine and is vulnerable to the belt being thrown off. This is not an imaginary scenario. My friend John Blackburn was killed in a Ford V-6 powered Mustang II from this exact scenario. On the handful of engines that I put a belt driven rear alternator on, I always had a belt guard that would prevent a frayed or thrown belt from getting to the ignition wires, and I always mounted the alternator on the opposite side of the distributor.

The only airframe that has a layout for a belt driven rear alternator that makes sense is a Pro-Composites Corvair Personal Cruiser. I built the engine and the rear alternator prototype, which is tucked in the place where the oil cooler normally is. It is well away from the ignition on the opposite side of the engine.  Over the years, we have sold several hundred front alternator brackets to builders who were choosing to make their installation a duplicate of the flight proven ones we promote.


2900- Front alternator bracket

Our front alternator bracket is a two-piece assembly that is CNC machined out of quarter-inch aluminum plate and then gold anodized. The two-piece nature of the bracket allows the inboard piece to be mounted on two of the 3/8” bolts going to the front of the case. The outboard section is bolted to the inboard with three AN-3 bolts. These two plates can be shimmed in relation to each other to allow perfect alignment of the belt groove with the alternator pulley. The outboard section forms a complete ring around the alternator to support it. It has a single mounting hole for bolting the outboard bracket to the cylinder head to stabilize it. The bracket set comes complete with full instructions.


2901- Mounting hardware

The inside of the alternator mounting bracket has holes for three AN-3 bolts to mount the two halves of the bracket together. We do not send these with the bracket because the length varies with the installation, depending on how the bracket is shimmed for alignment. These bolts should be finished with aircraft grade all metal lock nuts.

The outboard side of the bracket is stabilized by one bolt to the head. Depending on what year the head is, this bolt is either ¼”-20 or 5/6”-18. The length of this bolt varies depending on whether the engine has a 5th bearing or not. It is held off the head with a simple tubular spacer. The alternator bracket comes with detailed instruction on how to mount and align it.


2902- Permanent magnet alternator

The alternator we use is technically a permanent magnet AC generator. It has no brushes, has sealed bearings, can take over 10,000 rpm, weighs a shade over 3 pounds, is totally reliable, and costs under $150.  The only other thing I could ask for is that it be made in America, but it isn’t. It is made by Kokosan Denki in Japan. It is one of the few imported parts we use in the conversion.

You can’t buy direct from KD, they only sell to giant manufacturers. For a long time, we got these from John Deere dealers because they came on Deere tractors as original equipment. In the past 10 years, Deere has capitalized on the good name of their industrial equipment and moved into the homeowner lawn care market. Their dealers look like Harley Davidson showrooms. Over the years, they have been marking up their parts prices ever higher. The list price of the alternator is now well over $400, and retailers, with their green and yellow polo shirt clad sales staff, expect to get this kind of money from their upscale clientele who are their major customers.

Here is reality: John Deer tractors below 100hp all have had Yanmar tractor engines for decades. Once prices got high enough, I went over and found out that the part cost 1/3 as much if you buy it in a Yanmar box. The part number is 124190-77201. When we announced this on our website, an engineer for Deere got on the Web and stated that Yanmar parts are poor, and that the 300% mark up was justified by Deere’s quality program to make sure that they had a superior product. A very nice story for the members of the green tractor cult, but made of pure marketing B.S. I have bought dozens of both brands, and they are identical other than the box. Several years ago I met one of the chief engineers for Deere at Oshkosh, and he shared the entire history of Deere and Yanmar and confirmed that the parts are identical.

The best place to buy the unit is from Mike Schwab, a Yanmar marine parts distributor in Largo, Florida. He is building his own Corvair powered plane, so it is good to shop with friends. You can contact him through his website or by calling (727) 595-8813.

If you have a builder’s page online, avoid directly spelling out the exact source of your airplane alternator, as the legal team from the manufacturer might have something to say to their dealer about entering the airplane market.

As a back up source you can call or order from or (940) 592-0181. They have a website you can order from. If you call them make sure you do not mention that it is going on an aircraft, they have a note on their page about not selling aircraft parts. To my perspective, they are selling a part, your money is good, end of transaction, they are in charge of their business, you are in charge of your life.


2903- Alternator mounting hardware

The alternator is mounted to the bracket with a pivot bolt and a pinch bolt in the top slot.  The pivot bolt is set up as a AN6 (3/8″), the pinch bolt in the slot is an AN-5 (5/16″). Because there is a number of variables on type of front cover, Gold or Black hub, which 5th bearing, etc, it is best if each builder supply his own bolt length. The AN6 bolt does not fit the alternator housing exactly. The hole in the alternator housing varies depending on date of manufacture. If a builder would like a snug fit, a thin wall bushing can be used to bush the size down to the 3/8″ size of the pivot bolt. Both of these bolts should be finished with aircraft grade all metal lock nuts. The alternator brackets include detailed instruction on how to mount and align it.


 2904- Drive belt

For engines using a gold hub and a standard 20 amp alternator the correct belt is a Continental Conti-tech SF- AVX10 x 710. This particular belt provides several times the service life of more common belts. It is well worth getting one. For older arrangements with black hubs and previous alternators, we advise builders to measure each installation individually, as there are a lot of variables. Taking an old belt that is too long and cutting it into a form-fitting measuring tape is the best approach.

We have had a number of builders ask about using garden equipment belts, because they heard that one of the most common applications for the alternator is a John Deere tractor. This is true, but it isn’t the kind of tractor that homeowners or lawn service people use. Our airport has two of them for mowers; they have 5-foot-tall rear tires and they cut an 80” pass. The original equipment belts for the alternators are automotive style, not lawn service cross sections.