Aluminum push rod tube issue resolution.

Builders;

This commentary ONLY applies to aftermarket aluminum push rod tubes, which are  in maybe 3% – 5% of Corvair flight engines. If you have stock steel push rod tubes like the powder coated ones we sell, it does not apply.  However, the notes still make good reading and give some appreciation for detail design considerations GM put in the engine, and unforeseen potential consequences in modifications, particularly in combinations with other work.

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The original design of the aluminum tubes goes back more than 15 years. They were the work of Charlie Johnson, aka “One Sky Dog”. I’m pretty tight with Charlie, you can see pictures of the two of us hanging out at my place in Florida, building engines and shooting AR’s in this 2017 story: Last Engine of CC #39

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Part of the awareness of this issue with the aluminum tubes surfaced when we were building and testing Charlie’s personal 3.0L for an upgrade in his flying Dragonfly, read: Corvair powered Dragonfly, Charlie Johnson, aka ‘One Sky Dog’ .  The basic issue is this: When the aluminum push rod tubes are used in an engine with heads milled for a tight quench area, they restrict the oil flow back to the pan, and oil builds up in the valve covers.

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This isn’t a small consideration, I have seen a motor with 4 quarts of oil in it suck air into the pick up because it had filled each valve cover with 2 quarts, and it was in the process of ejecting a lot of it out the breather tube.  This wasn’t an easy issue to spot, because it is dynamic, and if you stop the engine and wait a few minutes, all the oil shows back up in the pan. Sight tubes on the valve covers confirmed the issue and the relatively simple solution.

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Above, is my own personal 3,000cc Corvair, (3,000cc Corvair (lower compression) engine), and you are looking at the #1 cylinder with the intake rocker removed. Notice there is  no space between the guide plate and the push rod tube. that is the normal path oil used to flow back to the pan. In operation, a lot of oil is pumped through the lifters, up the hollow pushrods, and sprayed out sprinkler style onto the rocker and the valve spring to cool them. It drains back by gravity through the push rod tubes, but it can’t be restricted. The stock steel tubes have never had an issue with this, but the following pictures will show why it is an issue with aluminum pushrod tubes.

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Above, same part of the engine from a slightly different angle.  The tube leaning on the head is a stock GM steel push rod tube which has been powder coated. Notice the wall thickness at the top is only .035″. This allows plenty of room for oil to flow between the guide plate and the tube. Now look at the Aluminum push rod tube in the engine. It’s wall thickness is more than 3/16″, .187″ This can block the return oil flow. The hole in the guide plate is where the pushrod goes, and in operation the pushrod is moving several thousand strokes a minute, oil doesn’t return through the space around the pushrod.

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PS: The photo shows a roller rocker, but I just removed these from the engine. I have a few hundred hours on them since 2004, but I opted to replace them with new, standard Elgin made in USA rockers as a pure reliability issue.

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Above, Why some Corvairs have used aluminum pushrod tubes without this being an issue, and why it is a problem in others: This is a very Common 3.0L Corvair set up. The “step” in the head, an upraised area where the head gasket sits, has been intentionally milled down to get a better “Quench clearance”. This in combination with any of our 2,775, 2,850, 3.0L and 3.3L engine kits with special designed dished pistons produces a very detonation resistant engine with a very desirable tight quench / moderate static compression ratio combination. We have built motors this way for almost a decade, but never encouraged the use of anything but GM steel pushrod tubes in them. Thus it was a long time before I saw the rare example of the dysfunctional combination. As luck would have it, my own personal engine had the combination, so I got to test and address the issue for other builders. My own engine has tested a lot of stuff, and in its details isn’t typical of engines we teach role to build for themselves.  BTW, we did nearly the same modification to Charlie’s personal engine which has aluminum tubes also.

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Above, on the left is the stock aluminum tube as they are made. I had these powder coated, like we do to steel GM ones.  On the right, the same type of tube which I just fed through my lathe. I shortened the tube .125″ and spend the end of the tube to give a generous oil return clearance around the guide plate when installed.

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Above, I was trying two different end treatments, but either one will work to resolve the issue.

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Above, proof of anything requires testing. Above is the engine with the modified aluminum push rod tubes running on my stand in front of my house.  Its green in the picture, but it wasn’t real warm. This issue shows up mostly on warm ups in cooler conditions, but if your engine has aluminum push rod tubes in it, this really needs to be checked and addressed.  Again, this doesn’t apply to steel GM pushrod tubes.

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15 or so years ago, when Charlie made the first set for himself, these rapidly because a hot discussion topic on the internet, particularly on the Corvaircraft list. People who had never held one, far less put one in a running engine, spent a lot of time talking about how great they would be because the set weighs 15 ounces less than the stock ones, and they must cool the oil.  I spent some time debunking the myth of cooling, as the oil in the head is at least 150F cooler than the top of the tube in operation. It meant little, as the discussion was dominated by people without a running engine who were sure their opinions were more valid than any measurement I took.

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For the record, Charle has not made any tubes in many years. He was never the guy driving the internet claims about them. Soon after he made a few sets, a west coast Corvair Car company made copies of them, and he drifted away from the project. In the end, this isn’t a tough issue to fix, but it is a lot more work than meets the eye because the heads have to be un-torqued to remove them, and without a lathe, it would be hard to fix. In the end it is a bit of a precautionary tale of how a small combination of alterations can produce things like the oil pump sucking air in an engine with plenty of oil in it. In the end, the great majority of builders are best served by very specific combinations of parts that we use every week to build very proven engines.

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Wewjr.

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PS; Something to laugh about: In the story: 2018 Zenith Open House -The long run., I pointed out the presence of a salesman, who was promoting an engine which had never flown on a Zenith, which he didn’t own, nor had ever even seen one run. For a moment, contrast that with the type of detail and testing above, and consider the 29 years I have been doing this and the 1,100+ stories on this site alone, and all the builds and engine runs, and colleges, and ask yourself what kind of person would listen to a salesman who has never even heard his Chinese engine run.

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The Barnwell SC Crew that brought you nine Corvair Colleges.

Builders,

Corvair College  #43 was the ninth College we have held in Barnwell SC. Although we have had outstanding events, both big and small from coast to coast and even in Canada, there is no question the Crew at Barnwell have lead the way on Colleges and have established an unbeaten record of service and good times to an entire era of Corvair builders. That type of contribution to our branch of aviation is exactly what makes traditional light aviation a real brotherhood.

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L-R, Brandon, Cal, P.F. and Tim.  Brandon is the young guy with 2 of the 9 Colleges on his scorecard, but the trio of the old guard have been with us at all nine Colleges. More than a decade ago, P.F. flew his Pietenpol to Colleges 12 and 16, and suggested I come to Barnwell and see the airport and meet his crew. He was very confident he had just the location and people we needed. Now, a decade later, hundreds of builders have learned exactly why P.F. could speak with assurance for his team and his airport.

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If you are one of the hundreds of builders who have beed a beneficiary of P.F and Crew’s hospitality and hard work, I really encourage you to share your gratitude in the comments section, its a mark of thanks they will appreciate.

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Wewjr.

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Carb Ice example from CC #43

Builders,

Over the years I have written a lot on this subject, but a couple of test stand photos can do wonders to illustrate a point that flight instructors rarely teach correctly anymore. For a much deeper look at the subject, follow this link: Critical Understanding #10 – Carb Ice.

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Mike Loevin’s Corvair, running on my stand at Corvair College #43.  The white section of the intake manifold above the carb is solid white ice, and it is 48F outside.

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The digital Thermometer shows the temp has dropped 30F going through the carb. There is identical ice on the inside of the manifold also. This is simple physics in action, and this is why planes have carb heat. Contrary to popular myth, injected engines do this also, they are jest less prone to quitting when the throttle is advanced when the pilot notices the rpm drop. No carb should be assumed to be immune to this. Popular hangar talk says Elison’s are not vulnerable, but cast right into the Elison body is the phrase “CARB HEAT REQUIRED”.

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Another look at the engine. Look at the prop blade and the balancer; its running. the power setting is 2,000 rpm and 20″ MAP, to break in the cam. This is about 50% power. If anyone tells you to wait until the engine is reduced to idle to use carb heat, they don’t know what they are speaking of.

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The picture above addresses one more myth, that it somehow need to be cloudy or rainy to get carb ice. Look at the sky in the picture, understand that anyone who claims you have to see dense clouds, fog or rain for ice to form is clearly mistaken.

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Just to reiterate it one more time, this isn’t a Corvair issue. Rotax and to some extent, Lycoming, avoid this somewhat by having full time carb heat, but every competent pilot should understand the fact it can happen to any plane, and they should take the engine manufacturers recommendations very seriously and ignore they hangar myths.

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Wewjr.

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Oil Fill Cap, Part number 1905.

Builders,

Every part that goes into a flight engine has its own part number in my conversion manual. The first two digits are the group chapter in the book. For example, lets look at the simple oil fill cap, #1905.

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Because it’s first two digits are 1-9, it is in chapter #19, the valve cover group. The manual explains how we set up engine valve covers, and how they have the crankcase vents on one side and the oil fill on the other. There are pictures and descriptions. The locations on the valve covers have very little internal oil spray, Oil can be added without removing the cowl, and you can also take the cap off and look at the #1 rocker and see which stroke the engine is on without the need to remove a spark plug. The locations on the covers have been evolved over time to make sure it clears all the cowls, etc.  A lot of thought goes into installation details that is not readily apparent at first glance.

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Above, six parts go in a yellow powder coated #1905 oil cap. L-R The blasted and coated cap, brass spring disc, main gasket, central washer, inner gasket and AN rivet.  We drill new ones apart, to have them powder coated yellow, the traditional oil filler cap color on US certified engines. I rivet them back together when done. Its elaborate, but these caps are included in our powder coated valve cover kits.  These are the covers you see on most of the engines at the colleges. If you are a good welder, you could build your own copy of them, and paint them and use the stock oil cap and save some money, but most people pick a color and have us send a set to them.

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Wewjr.

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New engines at Corvair College #43, and the “Signature Move” contest.

Builders,

Pictured below are new engines on my run stand at Corvair College #43 in Barnwell SC last week.  Every new engine makes a very important milestone in a builders project, but more importantly, it is also the affirmation they have really come to understand their power plant at a level 95% of homebuilders never will.

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The other side of this is more lighthearted; it is a great moment of fun when the engine which was just a collection of parts before, becomes a running, living creation, with just a second or two of cranking the starter. Ask anyone who was these, all of the engines pictured cranked up and ran in one or two seconds. Factory built engines bolted on by homebuilders without training or guidance don’t do that well. The difference is support and understanding. When your motor cranks up at a college, there are cheers and handshakes, and shortly after there is the traditional “Captain Morgan Pose” for the photo. Its all in good fun.

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This year, one of the six male builders pictured below Tracy had such a moment, but after a minute with the video rolling, I leaned over and said “Cowl Flaps are Open” aviation speak for your fly is down. This corrected, we took the “CMP” photo, and afterward he humorously added “Its my signature move”. We made some jokes about how this photo could go in his album with others from his 6th grade graduation to his wedding which would all have his fly open. Colleges are both serious training and good times with new friends.  If you think you know who had the ‘signature move’, use the comments section to cast your vote.

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Tracy Sheradin, with her Pietenpol engine. Tracy and her husband Dan we outstanding volunteers at the college.

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Larry Harris, who’s engine got off the stand before I got a photo. Thus I have the temp gun to show it is still hot on the bench form the Saturday morning run. Our pit crew worked so well the engines were hitting the stand on 65 minute intervals.

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Mark Spang with his Zenith 750 engine. He has attended all 9 Colleges we have held at Barnwell.

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Dale Sleep and his Zenith engine. Brisk weather and a smooth break in run.

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Grant Ziebell, and his 3.0L upgrade for his flying Zenith 750.

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Mike Loevin, and his new Sonex power plant. Mike attended several Barnwell Colleges, but brought his engine across the finish line at #43.

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Thomas Clepper, on the right, with his Corvair. He is setting the ‘Friends and Family plan record, because he has 5 other people started building their own Corvair. His running engine makes a powerful case for building your own.

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Wewjr.

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25 years after warning people, cast pistons still show up in planes.

Builders,

More than 25 years ago, long before the internet, I wrote my first Corvair manual, and printed it on a then modern dot matrix printer. In that manual, and in every one since, I have told builders not to use cast pistons in aircraft motors. I have never built a single flight engine using them, and this is not a new position. Yet, after all these years, people still put them in engines, and if they later resell that engine, it is frequently said to be ” Built to Wynne’s Manual”, a statement we would generously call “misleading”, the polite word for “dangerous lie.”

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The two reasons people put cast pistons in motors are they are cheap, and they are advised to do so by a “Local Expert”. If you want to read a direct story of this, follow this link:“Local Expert” convinces builder to use cast pistons. When you are done, please get a look at this story, and the links in it before buying anything: Junk you should not buy..

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Many people believe in “Let the Buyer beware” and I sort of do, but not in aviation where the penalties are pretty stiff. Truth be told, I have another angle also: When junk like cast pistons fails in a Corvair, none of the people who look at it say “That was not compliant with how William teaches people to build engines”  In almost every case, nearly every witness will only learn Corvairs=Bad. Most people are not very sophisticated in how they develop opinions these days, and they bring that to aviation, complete with a ‘facts don’t matter’ attitude.

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Many people know that a very large effort was put out by a law firm to blame me for a non-fatal accident several years ago. This is an extreme example of how people who don’t want to listen to my experience will not take personal responsibility for that decision. The facts: I didn’t sell the person a single part. I sent him 11 emails saying his plane was un-airworthy, including one the day before his 45 second flight. He refused, in email, to buy a timing light saying the previous owner must have set the timing. He was a 60 hour powered Parachute pilot with no transition training. He brought a passenger on the first flight. His Dynon recorded the CHT at 628F in 45 seconds into the take off.  He used low grade car gas for the flight and failed to conduct a two minute test.  All of this made no difference, they still wanted to get it into Federal Court in Arkansas. So If I sound heavy handed on this and not very libertarian, it is because after something goes wrong, the guy who made the choice almost never stands up and publicly says “This was my fault.”

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Above, these came out of a motor which a guy was actually building to fly. The motor was based on a Short stroke early Corvair, with a weak early crank, no 5th bearing, and plenty of other things I have told people to never do. If you look above, an irony: they guy used billet connecting rods with Chinese cast pistons. If you look at the underside of the piston there is a mark that is a G outside and N. It is a Chinese brand.  This engine was sold to a builder, who fortunately treated it as a core motor. It came to Corvair College #42 as parts. But someone who owned a manual of mine actually put this together to fly. If it was flown, it would have almost certainly broken, and caused a crash. How would you like it if a wealthy law firm claimed this was your fault? Welcome to our legal system. As I have said many times, I am a devout believer in the ideals of our nation, but the execution of those ideals can fall pretty short at times.

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Wewjr.

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The ‘two months salary’ rule applied to “Made in America”

Builders,

My neighbor Ryan called and simply said “It is here.” There was 15 minutes of daylight left, and we went out to my backyard range to experience an American masterpiece, a Freedom Arms Model 83, chambered for the mighty .454 Casull cartridge.

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Freedom Arms is company from Freedom Wyoming, and they make some of the finest revolvers in the world. The finish, fit and function on the 83 is unreal. I have been around firearms my whole life, and have not put my hands on better. The cylinder gap is less than .002″. For people who pathologically believe that everything imported, including their Prius, is ‘better’ than American made products, this is 3 pounds of evidence they are delusional.

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The accuracy and handing on it showed themselves right away. The fact this isn’t a target gun and it has more power than most rifles made its quality that much more impressive. I asked Ryan what he spent, and with a smile he said “I just went by the two months salary rule, because if you are really in love…”

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While it is a valid consideration that buying an American made firearm is an ethically superior decision to sending thousands of dollars to the DeBeers family so they can dig compressed carbon out of the ground in Africa with labor being paid slightly above slave wages, we can examine that at another time. My aviation connection is simple: We are surrounded by incredibly high quality mechanical products made right here by our fellow countrymen, and this includes a wide variety of aviation products, including good old Corvairs. 

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Besides, ask anyone who spent two months salary buying a diamond for someone they are no longer married to, if they would have rather purchased a Model 83, and I suspect the answer would be near unanimous.

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Wewjr.

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