Carb applications, choices people make


Yesterday at our airpark, 8 RV’s took off in succession, on 6 second intervals. At most airports this kind of flying is  forbidden/frowned upon/ illegal. At our airpark it is just called going flying. We only have 40 houses here and 64 planes, but we have a lot of activity. The skill level here is very high, 7 out 8 of the RV’s were flown by former USN attack pilots. The 8th plane was flown by a Vietnam vet, USAF F-4 Phantom pilot. Flying an A-4, A-6, A-7 or an F-4 doesn’t automatically qualify you to pilot a light plane.  But it is worth noting that often people who flew in serious settings have a different mental picture of what they want out of planes, how important reliability is, and the value of known proven information.

What does this have to do with Carbs for Corvairs? A lot actually. All 8 of the planes that left are very reliable performers, they have more than 500 hours on them on average, and you could start any one of them and fly it to the other side of the continent without mechanical consideration. Yes, they are all Lycoming powered, but more specifically, Every single one of them has a Marvel Schebler Carb on it.

The MA3-SPA we suggest using on a Corvair is the kid brother to the MA4s and MA4-5s on 320/360 Lycomings. (235/290 Lycomings used MA3s).  At a glance, most people can’t tell the difference between a 3 and a 4. They are of the exact same design, and for that reason, they have the same excellent reliability record.

I spoke with my friend Jeff Lange on the phone the other day. Jeff is a well-known VW pilot and an air racer. He is a mechanically clever guy, positive, friendly and out going. He is working to improve a friends KR/Corvair engine installation. The plane has flown about 100 hours on an Aerocarb, the very simple, red, floatless carb sold by the Sonex people. The KR builder did a great job on the airframe, but the engine install had some weak points. The fuel flow was restricted by having 9 (nine) 90 degree 5/16″ brass elbows in it. Additionally, the intake manifold that he fabricated had several vacuum leaks in it. Jeff was in the process of correcting these things.

The biggest thing that Jeff was having an issue with was getting the carb to be jetted correctly. Fuel flow at different throttle positions on an Aerocarb is determined by the taper of a 2″ long needle. Going all the way back to Posa carbs, VW guys in search of a really insepensive carb have often tried to make these carbs flow correctly by grinding a custom taper in the needle. This is not easy, and Jeff was now working on his fourth needle trying to get this to work. Let me first say that the Monnetts get these carbs to work on VW’s first by making the slide parallel to the crankshaft. For some reason, people who put them on Corvairs tend to miss this, which gives the engine poor left/right fuel distribution. Jeff is a skilled guy, and he certainly made the engine run better, but how good compared to an MA3? At the end of the conversation Jeff mentioned that he was looking into a carb from a jet ski as an inexpensive option. He may very well have something that could work eventually. But I have to ask myself if Jeff’s entry point into aviation had been seated in a F-4 headed to attack the Paul Doumer bridge instead of messing with VW powered planes would he have the same point of view? Probably not. These polar entry points are extremes. which end of the spectrum you gravitate toward says a lot about what you want out of your homebuilt.

The RV guys just want something proven that works. This is because they understood the value of reliability in machines that fly. In all their time, I can’t think of any kind of carb issue that any one of them has had, none of them has even taken their MA4 apart once, far less ground down any internal part to make it run. They fly very strong aerobatics every week, they fly to the mountains of Montana and Idaho every summer, and the fly without any internal adjustment to their carb even if it is 20F or 100F outside. Builders who have selected MA3’s for their Corvairs have had pretty much the same experience.

Is using a certified carb the only answer? No. People are free to do what they want, its their plane, their time, their goals. The only point that is very true, and is a hard and fast rule that I, in 25 years of being around experimental aircraft, I have never seen broken; You will not get the reliably of a proven certified aircraft component from something that is extremely low-cost and adapted to flight, especially if it is modified with a file and sand paper. You can’t have it both ways. Plenty of people have heard me say this before. Some people have an instant cop-out sarcastic emotional reaction; “I guess that means that we all have to fly certified Lycomings.” I don’t say it for that reaction. People who are really interested in learning don’t have emotional reactions to challenging thoughts. We are speaking of risk management of a finite budget, finite amount of time, and a skill set that improves, but isn’t going to make a guy into a fluid dynamics engineer in time to build a carb and go flying.

For each person there is a path and a reasonable answer, and I try to share my perspective and experience so that builders can make more educated choices for themselves. I want them to understand that there is marketing pressure to buy an EFIS, but an MA3, Stromberg or an Ellison will serve you better.  GPS is nice, but get a 5th bearing first. Rubber hoses, plastic barbed fittings and hose clamps are a great deal compared to AN fittings and braided lines, that is until you factor in the cost of skin graphs at $6,000 per square inch. (there is a bulk discount on them when you get 3 square feet, price drops to much more reasonable $1,500/square in.)

If every single homebuilt that was started got finished, They all had perfect reliability no matter what they had for carbs or other components, and if no one ever got hurt in planes, there would be absolutely no point to writing anything here. Home building isn’t a tee-ball game without score keeping. 80% of planes don’t get finished, it makes a big difference on what your installation is, and this isn’t a ‘sport’ like bowling, people can, and do get hurt here. Your personal politics may be against the death penalty, but understand that Physics and Chemistry are the two unswayable referees in the game of flight, and they both are known to bench players without consideration for good intentions or nice guys.

Here is the good news: success, reliabilty and risk are not random here. They are completely controlled by you and the decisions you make. It’s actually one of the things I like best about flying. No legislature is going to change the laws of physics. Play by the rules, and physics and chemistry become the most reliable allies anyone ever had. If your new to home building, your only task is to dispense with the consumer/marketing infomercial trash that fills most of our industry magazines and airshows, and get down to learning the real rules of the game, the ones that never change. It all begins with deciding who you’re going to learn from. Over time you will come to know that any system or product that promises an end-run on the unchanging rules is likely made of Unicorn dung, and that the very definition of reliability is a system that respects physics and chemistry and has harnessed them as allies.-ww

To show that my positions on these issues has never changed, I share a 2005 excerpt form our website below. If you thought my previous post about companies that promote plastic barbed fittings for fuel systems was unfair, get a look at the photo below. Don’t think about it being on me, or even what it would feel like on you. Take a minute to think about how you would feel about a child who was your passenger getting this kind of lifetime souvenir, and the free nightmares that go with it. Thats why it is completely ok to criticize the ownership of any company that promotes, sells, and profits from plastic fuel fittings in the cockpit.

2005-Maybe you just read all the above details and said “Those hose ends are too expensive, and my hardware store doesn’t have Adel clamps.” And then thought, “I’ll just use automotive fuel line, hose clamps and barbed fittings.” Let me show you the real reason why all the above details are worth incorporating in your plane. This photo is what my left leg looks like above the knee. This is a four-year-old skin graph. It actually looks fantastic compared to how it appeared the first year. Of course, my right leg, my right arm from wrist to shoulder, and right ankle match this photo. Besides this, another third of me got it also, but there weren’t enough grafts to put everywhere. Although my accident had nothing to do with the mechanical setup of the plane, you want to avoid at all costs putting yourself in a position where a rubber fuel line in an engine compartment provides you or your passengers with an opportunity to have bodily ornamentation like I do. Flying is a lot of fun. Creating airplanes is one of the great joys of my life. It will always involve some risk, but it need not involve stupid risks and poor craftsmanship. Everyone reading this can afford to do this stuff the right way and make quality parts that will serve you well. That’s what it’s all about.

“William, you ignorant troglodyte”…….(instrument options)


If you are old enough, you can remember when the last 5 minutes of the show 60 Minutes was given to Shana Alexander and Jack Kilpatrick for “Point counter point.” I thought of this when I read the first word in Andy Elliott’s letter. Andy and I are friends, and at the very core of this is our mutual need to get the other guy to concede an intellectual point, even just once. (don’t hold your breath for this, we are both stubborn and opinionated enough to qualify for honorary Irish citizenship.) Andy and I arrived in home building from polar opposite starts, so any discussion between us will cover a lot of perspective. In the end, each builder must decide what is right for his needs. Andy and I are just here to shed a little light…and get the other to see the error of his ways. For a little humor, the link below is Dan Aykroyd and Jane Curtin spoofing point counter point:!watch/2306 Dan Aykroyd always started his part by saying “Jane, You ignorant slut.” Thus the title of this story.

On the serious side, at the end of the letter I write a bit so builders can see something of the consumer/marketing forces they face in our industry. It’s the kind of writing that has not made me friends with ‘the system.’ Once upon a time I wrote almost 50 articles that were published by the EAA, I was on their masthead, I wrote for many other aviation magazines and was welcome on industry discussion groups. Over time people in our industry found out that I have never been a “go along to get along” type. If the industry has a dirty little secret to keep from builders, I am the wrong guy to tell. If there is an angle/system/ way-its-done that keeps things from builders, it is now understood that I’m not going to keep quiet about it. For this reason, I have a lot less ‘friends’ in industry than I once did. You write stuff like “Ponies vs Unicorns” and point out the new head of the EAA has a fake engineering degree, they don’t invite you to the cocktail parties anymore. Thats ok, I got into homebuilding to learn, build and fly, not be part of a marketing industry.

From Andy Elliott:

Counterpoint:  – Some of us *do* have flying missions that take us far from home, over nearly unpopulated mountains and deserts, day and night and in the clouds, and therefore require more than a minimalist VFR panel. I wouldn’t disagree that many people install way more avionics than they will ever need or use. (I saw a Grumman Tiger once with a 530/430 combination, a two-axis autopilot and a 496 on the canopy bow, where the pilot was not and had no plans to become instrument rated!) But that doesn’t mean that modern computerized avionics are “bad”. It just means that some people are not thinking clearly about the mission vs. value proposition.
I don’t know why you’re on the warpath against MGL. IMHO, they offer a wide variety of useful instruments, RF and EFIS/EMS products that are highly customizable, are specifically designed for experimenters and amateur-built aircraft, and have a pretty good price vs. performance ratio. They are built by a small private company where the president and CEO does most of the engineering and testing, that supports its users, and that has real pilot/engineers providing excellent customer service out of an office in Torrance, CA. They’re not a Garmin by any means.
I am not a fan of Apple, but I do carry a $200 Google Nexus 7 (Android) tablet in the plane. It’s built by Asus in Taiwan, an erstwhile long-term ally of the US, not the People’s Republic. My $100 annual subscription to AnywhereMap on the tablet means I never have an outdated chart, never am missing the approach chart for somewhere I end up after diverting, and always know the TFRs, at least as they were when I took off.
The Nexus 7 has a much better built-in GPS than the iPad (and better than the Avmap in the plane!) and also has excellent 3-axis accelerometers and gyros that work as well as my MGL EFIS. For $5 (Yup, five!) I found an app called “Flight Instruments” that serves as a backup EFIS, equivalent to the $1400 unit that Dynon is foisting on the community. I think this is a major flight safety improvement.
So I think the key point is that the builder should *think* about putting in a panel that is *appropriate* to the plane and adequate for the mission being flown. One size does not fit all.
Andy Elliott
515 hrs since Nov 2008

Andy, To start with, I have to object to your use of the acronym IMHO, as anyone who has met you will testify you have opinions, but not humble ones. In all seriousness, I think your letter does a good job of illuminating some well researched options on the other end of the instrument options. We are certainly in agreement that no instrument of any kind is a substitute for pilot skill. From an engine builders perspective, I think that anyone flying over unforgiving areas first and foremost needs to have a first class engine and airframe. I have seen a number of planes that have $5,000 in the panel but don’t have a 5th bearing or a decent set of heads. I am all for what ever people want in front of them after they have addressed reliability ahead of the firewall. I am also going to point out that it is human nature to gravitate toward things that operate on skills one already has. I am not speaking of my love of mechanical things: My point is that many people spend hours learning to program their GPS, because working with computers is a skill they already have. I meet many of these people a year who have not devoted 10 minutes to learning how to use a timing light or a differential compression tester. Anyone who bought an EFIS before owning both of the other tools needs to re-think wether or not they are interested in learning about an engine, or are they just viewing their Corvair as something cheap to pull the panel through the sky.

On the subject of MGL, here is my issues: A) For a long time the promoted a plastic barbed fuel flow unit as airworthy and suitable for installation in your cockpit. People covered in skin grafts are allowed to call this amoral. B) In the last 12 months they sent an email to a 601 builder telling him to directly wire his tach to the ignition, which made it fail (on the ground.)  C) I have had several of their sending units fail., and D, the big one) They have a marketing strategy that makes every tom, dick and harry a dealer. Here is why: They offer virtually anyone with a .com website a dealership. You don’t have to stock anything. If a person clicks on the link on your site, the order actually goes directly through MGL, and drop ships from them, and they instantly pay you off with 20% of price. How this works for MGL is that they have people everywhere who simply appear to be a friendly voice offering testimonials about their products. These people write for every magazine, are on every large email list, and work at nearly every experimental aviation company. To a builder that is yet to understand how many pockets are getting lined, MGL appears to have incredible grass-roots appeal. Take away the money, and most of the testimonials dry up. As long as the money is there, builders will get an endless stream of stories selling them on the idea that this stuff is a “must have.” The strategy works, because there are many Corvair powered planes with MGL avionics but no 5th bearing. I have had a number of builders say “I like MGL because when I email them they send an email back in minutes!” If the email they sent back told you to hook your ignition directly to the tach signal, they are just a marketing tool, not an asset to home builders.

The only positive note I have on MGL/Corvair stuff is that MGL recently made Dan Weseman a dealer. He didn’t even ask about it, they just sought him out because of the Panther project. MGL has made several other people ‘the corvair dealer’ before, but has never contacted me on this. I don’t take this personally, I don’t think they know anything about corvairs or who has developed them. If they think that Dan is going to blindly sell stuff to people, they are mistaken. 5 years ago he developed a tach sensor for an MGL that works off the flywheel. It has hundreds of flight hours on the “Son of Cleanex.” This is the system that Dan would like to steer MGL users to. I have no doubt that Dan would advise any builder that an EFIS of any brand, is something you consider buying for your corvair powered plane after is has a 5th bearing and a real carb.-ww

Heavy Duty Gold Oil Systems, new cooler model.

Note: If the picture is small, try hitting F5 on the top of your keyboard


For the last 6 years we have been offering Gold oil systems. The basic element of the system is the Filter housing, which comes in forward and reverse models. There are a number of posts on these parts here on this site, and also on  our main page,

Some aircraft, particularly larger, slower climbing ones, benefit from having larger than stock oil coolers. The Gold oil system is a ‘modular’ system that accommodates this. The additional parts in a HD oil system are the Sandwich, a block off plate, two oil lines, and the HD cooler. These parts cost a builder about $500 to up grade to the HD system. The HD system has roughly 2 to 2.5 times the oil cooling capacity of the stock system.

The HD system has been long proven on many large slow climbing planes. Our work with it actually predates The Gold oil filter housing. On the ‘black’ HD oil systems we mounted the oil filter and sandwich on the firewall, in a configuration knows as a ‘four hose’ set up. We flew these in 2004 on our own 601XL, and later installed them on a number of larger, slow climbing planes. The Gold oil system was an improvement aimed at having all the same functions, but keeping the components all mounted on the engine, and utilizing a much more compact and simplified arrangement. It also ended up costing builders slightly less than all the elements of the previous ‘Black’ system.

One of the hallmarks of the system is that it is designed to directly work with all the other systems we promote. Adding an HD system doesn’t start over from scratch with a builder: the Sandwich goes between the Filter housing and the filter; the larger cooler fits directly in the baffling kits; the arrangement fits inside all the cowlings we sell; The system fits with all of our motor mounts and intakes. It even clears the new rear alternator arrangement.

This particular story is about a new cooler we are working with. The two photos below are a little fuzzy, evidently I didn’t have enough coffee when I was holding the camera, however they have enough information to give the general arrangement. The installation pictured is our Zenith 750 fire wall forward display, with a mock-up engine on it. In addition to displays at airshows, I use the unit to test fit lots of small detail items on installations. Some people like to look at drawings or CAD files, but nothing is as good as having the assembly in real life in front of you. Now that Americans spend half their waking hours staring at a screen of one sort or another, Reality is going to have to stage a big marketing campaign to win back people’s attention. Maybe reality needs a catchy slogan like “We have always been 3D! or “Available in high definition every where.” I appreciate that builders can get info here, but unless the time ratio of shop to screen is about 10-1, your plane isn’t going to progress quickly. Read the information, understand it, and then go to your shop and put it to good use.


Above, the new cooler in the baffling. The Cooler is an Aero-Classic 9 row cooler. It is the same size as a Niagara 20003. It is a fully certified, FAA-PMA part. It is available from Aircraft Spruce as part number 08-00641. It sells for $248. I still like the Niagara’s, but they have gotten astronomically pricey. This one is about $140 less. This cooler is bigger than the 20002 that we recommended for installations like 601’s. The 20003 we recommended for aircraft like the 750. In Niagara’s system, there is a large price increase between the 20002 and the 20003. In Aero-Classics, the 7 and 9 plate coolers are only $4 different. The weight difference is minimal, and I would recommend that everyone interested in a HD oil system just opt for the 9 plate model. If it is too cool in the winter on your 601, you can always partially block it off with a tiny piece of sheet metal.


Above is the other side view. This shows how well all the different elements fit together. In the Gold oil system, everything is mounted on the engine, and it all moves together. I actually greatly prefer this to firewall mounting oil system parts. Most common question is about oil spilling during changes. Very little does, the filter has an internal check valve that prevents this. In its original application the filter is on top of the car’s engine upside down. The lines are Earl’s AN-6 units with swivel seal ends. In the last few months I have been working with a CNC tubing bender that produces aerospace lines, looking at having robotically bent stainless hard lines made to replace these two hoses. It may be a long term option, but at this point I am staying with good old braided lines. The reservation issue was about preserving the systems ability to fit all airframes. To get the radius on the hard lines we wanted required an investment in tooling or a quantity purchase that would cover well over a years worth of hoses. Before we take either of those options I want to see the final configuration of the Panther’s cooler location, study how it also fits into a high thrust line Pietenpol cowl, and make sure it would leave open the option for an increased capacity rear alternator. All of wich are about good strategic planning on my part, but each builders aircraft is a tactical problem to be dealt with in a proven way today. The cooler and lines in the photo are in a box on the way to a Zenith 750 builder who is planning on flying his plane by the last day of the year.-ww