William Wynne

"The Corvair Authority"
5000-18 HWY 17 #247
Orange Park, FL 32003

Midwest Corvair Night Schools in Feb. 2005

Open E-Mail

December 2004

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Subj: Ignition Questions
Date: 12/29/04

Boy am I glad to see our new Q&A page open. To start this new adventure in getting answers, I found you recommend two different coil setups: a Bosch #00012 with built in resistors and an Accel Super Stock with CR-10? ballast resistors. What is best in your experience? And what condensers P/N?

Next questions: I have restored several old aircraft with unshielded ignitions and built a few VW and Subaru engines up for homebuilts for myself and others and always had the same end result: a good flying aircraft with no radio. Have you or do you plan to address this radio noise problem publicly on your Web site? (I hope so.) I have had a lot of people ask me what to do about it, and I can only tell them to try this or that, but be careful not to create any potential shorts. I plan to get serious about this problem on my Corvair/Wagobond project. Any help you can give me will be greatly appreciated. I want to cut my R&D time as much as I can, but I want to solve the problem for anyone concerned. I hope we can communicate regularly. I would consider your input on this as very valuable. Note: I have a very good friend who has a pacemaker who is afraid to fly in an experimental aircraft because of radio noise interference. He thinks it could stop his heart!! I do not know, but I intend to find out and hopefully solve that problem too. I will keep you posted as yet another R&D project continues.

PS: I received your E-Mail and my Prop Hub Hybrid Studs. Thanks!

Yours truly, Jack Nelson, Manual #5134, Corvair/Wag-o-Bond, 90% finished 90% to go! Ha!Ha!, Livingston, Texas

Reply from WW:
It was good to have you as a guest at Corvair College #8. We flew Accel coils for years, but the 601 and many of our customers' planes use the Bosch coils. I prefer these over the Accel because they do not require external ballast resistors. We've recently started to look at a substitute for the Bosch, an IC675. It is available from any NAPA store. It's lighter and smaller than the Bosch, requires no resistor, and can be mounted at any angle. One of our Canadian friends recommended it, and we've used it on our dynamometer, but have not yet flown it, although I have little doubt it will be our new choice. The condensers we use with any coil are the standard NAPA condenser for the Corvair. You'll need two; one for each coil.

We have a King radio in the 601. We've used handhelds in all our previous airplanes. The majority of our customers' aircraft have radios. I have absolutely no reports of ignition noise on any of these radios with our system. I credit this mostly to the spiral wound wires we recommend in the Conversion Manual, and the fact that points ignition systems traditionally make less radio interference than most types of electronic ignition. I would not be concerned about using a radio with our system. Experience has shown it's not an issue. You'll need to get in touch with some really electronically savvy people to evaluate concerns of your friend's pacemaker vs. aircraft equipment. Sounds like an interesting project, though.

Subj: Cores
Date: 12/29/04

I have access to a fellow with lots of Corvair engines for sale. Good condition, but none of them are assembled. I picked up enough parts to make 2 engines. Most parts are pretty easy to say yes or no on. And some I just got for cores anyway. But what's the deal with engine cases? Are they all pretty much the same thing? I can't see any differences visually between the various years. I thought maybe the crankshaft holes might vary over the years at least. I am glad I got 2 of everything since one case has an extra oil galley return hole drilled in an odd place. I would weld it closed with my Tig, but I keep blowing the house circuit breaker at that high an amperage. Woohoo!

Mike Studer, Cassutt, Newark, CA
Reply from WW:
All Corvair engine cases have most of the important dimensions in common. But, the main difference is that 1960-63 cases will not allow the longer stroke of the 1964-69 crankshaft without significant machining. Thus, your primary case candidates are the 1965-69 engines, and the 1964s. The 1965-69s are easy to id because 99% of them have an "R" for the second to last digit in the engine case code. For example, RR, RD, RA, RH. The 1964s are easy to identify if you know what to look for. The '64's case code will not assure you of identifying it. There are 1964 YN engines which have the long stroke crank and the internal clearance for it, and there are 1961-63 YNs which are short stroke engines which would require machining for long stroke crank clearance. In the land of Corvairs, a long stroke case is referred to as a "relieved" case. Anyone who knows Corvair engines can show you the clearancing done by the factory inside the case. There are good drawings of this in The Corvair Junkyard Primer, a booklet available from Clark's Corvairs.

Tig welders draw an impressive amount of current when set on AC. I tripped the breaker at our old hangar a zillion times. The breaker box was all the way at the end of the hangar row. The experience was a real vocabulary expander. Our new hangar has a 100 amp circuit for the welder. Be cautious about excessive welding on the case. You want to avoid having any type of slag enter the oil system.

Subj: West Coast Corvair College
Date: 12/28/04

I heard a rumor that you may be coming to Southern California to present a Corvair College this spring. Might that be happening at the EAA hangar at Compton Airport? There are a couple of us (likely many more) who would attend from the Left Coast.

Warm regards, Randy Stein
Reply from WW:
We had a great time at Corvair College #5 in Hanford, Calif., in January 2004. We've given a lot of thought to returning, even for a brief one or two day event. I lived in California many years ago, and it only took our brief visit to remind me that the work hard, play hard motto was probably invented there. Our learn, build and fly motto and enthusiastic approach plays well with builders of high initiative. Although it's a long way, it's never too far to travel to meet more builders who feel this way. We're going to publish our 2005 season schedule on our Web site about mid-January. We're strongly considering a West Coast event. We'll let everybody know.

Subj: Valve Job
Date: 12/28/04

I'm doing the valves on those heads you welded up for me at Corvair College #8. I've got stainless exhausts but can't find the intakes. Can I use the stock or "tuftrited" ones? Also, couldn't find a part number for the valve springs in the Manual.

Great idea going to this "Open" format.

Lanny Bissell, South Carolina, Manual 6143

Reply from WW:
We have hundreds of flight hours on both stock valves and aftermarket stainless valves. They both gave good service. We use stainless steel intake and exhaust valves in engines which we produce because I know that they're better than stock valves, at a modest increase in cost. The exhaust valves in the engine work at a higher temperature than the intakes. If I were going to choose intake or exhaust, I would put the stainless valves in the exhaust. If you still would like stainless intakes but can't find them, let us know. We can probably find a set for you. The TRW valve spring part number is included in the back of the Manual. It's good, but lately we've had a lot of success with springs from Jeff Ballard at SC Performance. His number is also in your Manual in the 3100cc section. We use digital scales to carefully test every valve spring going into an engine, and the ones from Jeff are very consistent and are exactly the rate we like for the OT-10 cam. Additoinally, they're not very expensive.

Subj: Can I Mix Case Halves?
Date: 12/28/04

I have two engines that I am disassembling with hopes of building one good engine for my 601XL. Neither engine has a pair of perfect case halves. In the first engine, one half has good studs but on the other half I was forced to cut or remove 4 studs. The second engine has two rods (#5 and #6) broken at the crank end. As the engine self-destructed something broke a finger-sized hole opposite cylinder #6 in the "odd" case half (cylinders 1-3-5). Both engines are "RH" blocks (both from 1965, I believe).

So what is the safest route - repair the cut/removed studs and keep the original pair together or take the good halves from each engine?

Craig Payne, Park City, UT, Manual #6154

Reply from WW:
It is bad practice to mix case halves. 1960s machining technology leads me to believe that the case halves are not interchangable with each other. If you did assemble it, and it rotated, I do not believe that the engine would be long lived. You would be far better off making the repairs to keep the original case halves together. Remember that a pair of cases for a Corvair is never worth more than $100. So, if it looks like heroic measures would be required, simply get another case. In all my years of working with Corvair engines, I've seen just a single car engine, which apparently ran, that was made from case halves of two different years of Corvairs. I would not follow this example. I would always use a set of case halves that left the factory as a machined pair. This advice is not just for Corvairs, it's standard practice on Continentals and Lycomings also.

Subj: Motor Mount Bolts
Date: 12/27/04

I have the WW Motor Mount on my 601XL. The motor mount bolts are from Zenith and were produced for the O-235 engine. When the mount is placed on the bolts, the spindles of the mount are short enough that approx. 5/8" of non-threaded bolt protrudes beyond the spindles. What is the recommended method to fill this difference so that the nuts can draw up properly? I noticed on the WW 601 that the bolt heads are resting on the spindles and the nut is on the inside of the firewall. In the Zenith motor mount bolts, they are welded to brackets that attach to the upper longerons and the nuts are on the engine side of the firewall.

Gary Ray, West Bloomfield, MI, 601XL
Reply from WW:
The Motor Mount on our own 601 is one of a kind. Although it's dimensionally identical to the ones we produce in terms of engine location, the attach points to the firewall are reversed from our production motor mounts. The spools, the part of the motor mount through which the bolt passes, are 38mm long. This is the same as the motor mount shown on the 601 plans page 6Y-E-2. This page contains the drawing of the O-235 Dynafocal mount. You can compare the length of your studs to these studs. There's some discrepancy with your mounting bolts, but it's not a big issue. Either you could use shorter bolts, or we'll machine you a set of spacers to go between the nut and the motor mount.

Subj: Fuel Pump Bushing
Date: 12/26/04

I just assembled my engine with the rear case mounted. I left the fuel pump bushing in. Can I either pull it out, or stuff something in it to catch the chips and cut it off?

Thank you, John Monday, KR-2S, Laguna Beach, CA
Reply from WW:
I pulled one of these out of an assembled engine just today. I used the threaded rod and tube style puller. A 3/8-16 rod will slide down the middle of the guide. Rotate the engine so that the eccentric is in a position to give you the most clearance below the guide. A standard nut can be ground down to an outside diameter smaller than the OD of the guide. Using some very long pliers, you can hold this below the guide and thread the rod into it. Playing a propane torch over the guide area for one minute will allow the aluminum to expand and make drawing the guide out easier. The alternative, as you mentioned, is cutting it off. Packing the area with greasy rags to catch the chips and then using a Shop Vac to clean up all the chips after cutting, before the rags are removed, is effective if done carefully. Be very cautious not to nick the gasket surface. More information on this can be found on the Oil System Page.

P.S. A follow on to your earlier question about vacuum pumps. Vince and Louis, the 601 builders/airline pilots from St. Louis, recently showed me a completely electronic attitude indicator. It was part of a glass panel display that they're planning on installing in their 601. When they showed me the price, it struck me that the end of the vacuum pump and mechanical attitude gyro era of experimental airplanes was coming to a close.

Subj: Valve Adjustment on Stored Engine
Date: 12/23/04

It was suggested that I do not adjust the valves on my Corvair until I am closer to having it run (probably a couple of years until I get the bird done). The thought is that the valve springs will retain memory of being left in a compressed position too long. I have old cars out of fields that have been abandoned for 20 years, dumped some Marvel Mystery Oil in the cylinders, broken the crank loose with a breaker bar and fired them up and have run great! What is your opinion on adjusting the valves and letting the motor sit for awhile?

John Monday, KR2S, Laguna Beach, CA

Reply from WW:
In the Conversion Manual, when I discuss valve springs, there is a nod given to this same thought. However, my fundamental feeling about the nature of springs is that a quality spring would not care if it were compressed for any length of time as long as it is not forced past its yield point. This said, certain types of metals under stress are more prone to corrosive attack; in the case of a valve spring, rust. In a nutshell, for these reasons we always replace the valve springs when we rebuild an engine. With new valve springs, in a noncorrosive environment, I do not think the springs being compressed is an issue. I have stored engines, with the valves adjusted, for two years without turning the crankshaft and experienced no problems. If you do wish to adjust your valves and store your engine for a lengthy period of time, you must take the effort to seal your intake and exhaust ports to prevent air from entering the cylinders through open valves.

Subj: Prop Clearance
Date: 12/24/04

I think this new idea, the Open Email, is a great way to cut through all the other noise on the Internet and get straight to answers I can use! Thanks for doing this. Please keep up the good work.

I just installed my 66 inch Warp Drive prop on my 601XL Tri-gear and I noticed that I have about 7" of ground clearance. That doesn't seem like much to me. What are you guys flying with for ground clearance? The engine mount is your stock William Wynne model.

Thanks, Phil Maxson, 601XL/Tricyle/Corvair, N.J.
Reply from WW:
Seven inches is more than you're thinking for a number of reasons. First of all, certified airplanes are primarily required only to maintain positive ground clearance with a flat nose tire and a collapsed strut. If you look at a Cessna 150, 152 or 172, they will not touch the prop to the ramp with a flat tire and a flat strut. But I doubt they have much over 7" of clearance under normal circumstances. The 601's nosegear does not have a ton of travel, nor does its small sidewall nose tire lower the nose much if it's flat.
Keep in mind the major issue here is that your aircraft is not yet in its flight configuration. Airplanes without wings or passengers are nose heavy. Adding the wings or the crew will tend to load the main gear and not the nosewheel. Under these circumstances, you'll have more than 7" ground clearance at rest. Over the years, we've operated a number of aircraft with far less propeller clearance. Props have to be very close to the ground to pick up trash, pebbles or gravel. The major reason experimentals occassionally have a prop strike is taxiing over very uneven ground with 4 or 5" of clearance. As a final note, consider that the standard 601 propeller for the factory Jabiru 3300 installation is a 68" diameter Sensenich. The thrust line of the Motor Mounts that we build are at the same level as the factory 3300 Jabiru. Thus, you have even an inch more clearance than the factory recommends.

Subj: Front-mount alternator brackets
Date: 12/23/04

Do you still intend to offer the front-mounting JD alternator brackets for sale, and if so, when?

Thanks, and Best regards, Don Lawrence, California
Reply from WW:
We're getting the first ones back from the CNC hydrocutter shop this coming week. I anticipate that it will be a very popular product. We have about 50 flight hours on ours, and it has worked flawlessly. The finished product will be nearly identical in dimensions to the handmade prototype pictured on Our September 2004 601 Web page. We'll post a notice on www.FlyCorvair.com as soon as they're ready for shipment.

Subj: Corvair Powered Piet
Date: 12/22/04

I'm still slowly working on my Corvair engine and on building a Pietenpol. This current series of questions has more to do with those two playing together and your recommendations. Basically, looking over Bernard Pietenpol's plans, the Corvair engine mount seems to have a significant downward pitch. This still the right way to do it?

Any suggestions on maximum diameter prop that would work?

And, any experience with the biplane varient of the Piet known as the Aerial (from St. Croix). I am trying to learn more to see if it might be viable.

Thank you, Jon Apfelbaum, Pietenpol, Utah
Reply from WW:
My Pietenpol is perhaps the only airframe to be flown both ways, with both Bernard Pietenpol's low slung motor mount down thrust in it, and later with the motor mount raised 4" so that the thrust line was level with the top longeron and built with no down thrust. It provides a dramatic difference in the appearance of the airplane. Any photo you see of my airplane when it's painted orange is the original Bernie mount, and all pictures of it when it's navy blue are with my mount. There was not a tremendous difference in the way that the airplane flew. It certainly flew no worse with the later motor mount. I largely think that Bernie maintaining the low thrust line was mostly influenced by his retaining the stock blower fan and keeping the thrust line in common with Ford Model A powered Piets. With our more compact electric start installation, I was free to move the engine up in the airframe. A lot of down thrust is common on airplanes which may be climbing at very slow air speeds. We used 60-65mph as a climb speed on our version of the Pietenpol and never felt the need for down thrust.

Most stock Bernie mounts utilize 66-68" diameter props. There are many different variables in landing gear design on Piets. Some people build their planes with very short legs, which cuts down on prop clearance. With the motor mount raised 4", we could have swung any prop we liked, but chose 68" for performance reasons.

There have not been a lot of Pietenpol Aerials built. The Piet does not have a gigantic tail. I strongly suspect that adding a second wing, without changing the size of the tail or length of the fuselage, would effect the stability in an unfavorable manner. In my humble opinion, there are many other better light biplanes which could be Corvair powered, like a Hatz.

Subj: Oil System info
Date: 12/26/04

What do you expect the new oil top cover to cost? I think that for my application with the turbo it would free up a lot of space and allows greater flexibility in the turbo placement. Please let me know how much so I can budget some funds for this component.

Hopefully you had a good Christmas and I hope you have a happy new year.

Best regards, John & Jean Kearney, 601XL, Nevada

Reply from WW:
The machined Oil Top Cover Plate with installation hardware is available for $69, which includes Priority Mail shipping inside the U.S. This part goes a long way toward cleaning up the engine compartment and providing more space to lay out a clean installation, whether it's turbo or naturally aspirated. You can see the whole story on the part at www.FlyCorvair.com Oil System Page. There's also several photos of the prototype now flying on the 601 Web Page, and you can also see several of these installations on customers' engines at the Corvair College #8 Pages.

Subj: Tachometer Coil Pickup
Date: 12/23/04

I listen and read stories about Tachometers optical and off the wire. What is wrong with a coil or distributor tachometer pick up? So simple so dependable. Yes they can short a coil but not with a low amp fuse.

Wayne B., Pegzair, Canada
Reply from WW:
I discourage people from using regular automotive aftermarket tachs for just the reason you point out, the potential of shorting out the coil. However, your point is good, that if it has a fuse, it is unlikely that a faulty tach could take out the ignition system also. Although I have not flown a Corvair engine in this configuration, Dave Blanton's V-6 Ford conversion manual recommended a 1/2 amp fast blow fuse for the tachometer circuit if a regular automotive tach was to be used. Personally, I like the Stewart Warner tach we have in the airplane because it has very smooth operation, and is completely independent of the ignition system. The full sweep nature of the tach and its 0-3500rpm scale make it appropriate for our application. Most auto tachs go to 6,000 or 8,000rpm, and we'd therefore only utilize a very small part of the scale, thus making it more difficult to watch for ignition and carb heat rpm drops during the pre-flight run up, let alone slight rpm drops during flight, which is the indication of the onset of carburetor ice.

Subj: Which spinner?
Date: 12/21/04

I see three different 13-inch spinners for sale by Van's: ones for wood, Sensenich, and variable-pitch props. Which one do you have for your Warp Drive prop? I notice that the one shown on the Web page had no slots in it in the early stages.

Steve Mineart, #5833, CH601XL, Iowa

Reply from WW:
The Van's spinner we use is Part No. FP-13. This is the standard spinner we're going to use on virtually all of our installations. Our Front Bulkhead and Crushplate Assembly allows the use of the comparatively thin Warp Drive prop with this deep spinner. We're currently working on an elaborate jig which will allow us to match drill the spinner to the bulkheads for you. This will save the first-time aircraft builder from the time consuming task of getting the spinner perfectly true. We're shooting to have this tool done by the end of January. We'll show it with pictures on www.FlyCorvair.com as soon as it's finished.

Subj: Carter YH Carb
Date: 12/21/04

You answered a lot of questions about carbs in the past, both in the Manual and on your Web site. I wonder if you have ever tried using the Carter YH side-draft carb that comes on the 180 turbo Corvairs? Seems like it might be a natural fit if you don't plan to use a mixture control. I personally have already acquired an MA-3SPA that I plan to use, but I have always wondered about the Carter YH.

Thanks, Dave Morris, Dragonfly, Texas
Reply from WW:
You think like Bernie Pietenpol. If you read Bernie Pietenpol's notes from his experiments in the 1960s, he mentions using what he calls a Spider carburetor, which Corvair car people know as a YH off an early model turbo engine. He noted that it was heavy, and prone to icing, an assessment which holds true today. YH is also the original carb from early 6-cylinder Corvettes. If you check out the overhaul price, it's actually more expensive than many aircraft carburetors. It also has many cast iron parts, which make it heavy and potentially damaged by corrosion.

Subj: Oil Pans
Date: 12/21/04

I received the oil pan today. It looks great. Thank you. What was the new method of attachment so as not to have to safety wire the bolts around the pan?? You had told me when I was there, but I did not write it down. Thanks--

Joe Horton, KR-2, Coopersburg, Pa.
Reply from WW:
The most popular companion piece to our Light Weight, Deep Sump Oil Pan is the Oil Pan Installation Kit. It contains all the fasteners, a modified oil pickup to reach to the bottom of the pan, a drain plug, and instructions. These kits come two ways: One is with drilled head stainless Allens which you safety wire after installation, and the second is with steel studs, which you Loctite into the case and use with all metal AN locknuts. We charge $49 for the Install Kit. We'll send the Kit with either hardware if the customer has a preference. Shortly, we'll integrate both into a single, complete kit. But they appear currently as two separate parts at The FlyCorvair.com Online Catalog because the Oil Pan's introduction pre-dates the hardware kit by several months.

Subj: Starter Ring Gear Change
Date: 12/21/04

My manual (#5597) recommends a Nissan Sentra 10-1/2" ring gear. I'm assuming the stock Subaru starter will mate to this and turn the ring gear. Recently I have seen that you are now recommending the Ford Taurus ring gear and changing out the starter gear. My question is, what will I be sacrificing if I choose to use the stock starter gear and the Nissan Sentra ring gear that I purchased when I first received my mMnual from you a year and a half ago? Thank you for your help in this matter,

Scott Laughlin, Manual #5597, Omaha, Nebraska, 601XL/Corvair, 75% complete
Reply from WW:
The Nissan arrangement is a perfectly good setup, and is flying on a number of our customers' airplanes. We went with the Ford because they're about a pound lighter, and far more available. We buy them by the dozen, whereas the Nissan had hit or miss availability. If you have the Nissan gear, go with it. It's not a big issue. But everyone who's yet to pick one up should use the Ford.

Subj: Jabiru J250
Date: 12/22/04

It appears that the Jabiru J250 would meet our needs but I still believe that the Corvair is the best engine for me. Have you any experience with Jabiru airplanes? Thoughts on the match? Considering developing mount and related items for installation? It could easily handle the weight and seems appropriate in HP. Thanks in advance,

Tom Kelso

P.S. I have the Manual and too many cores along with too many cars.

Reply from WW:
One can never have too many cores or too many cars. We keep six Corvairs at the hangar. I have one, Gus has one, and Kevin has four. Additionally, Kevin has one at home, and has a van awaiting pickup in California. You two would get along great.

Few people know that Jabiru has a line of aircraft in addition to their engines. It would be very ironic indeed to have a Corvair motor on a Jabiru airframe instead of the obvious Jabiru engine. This appeals to our sense of humor. If you buy the airframe, we'll make you a custom motor mount. Our friend Gary Coppen owns the Corvair/Skycoupe. The Skycoupe is designed by Ray Stits of Stits covering fame. Gary has to be the only guy in the world who covered his Skycoupe in Seconite. He always jokes about getting a photo of Ray Stits standing in front of the Skycoupe. It's the same kind of humor considering a Corvair powered Jabiru airframe.

Subj: Valve Seat, Distributor Clip
Date: 12/22/04

I have a couple questions. I'm not building presently but have three engines (1 disassembled). One of my engines pulled the valve seat out and had been run enough to considerably enlarge the hole (about 1/4 inch). Do you think this can be realiably welded and remachined?

The other is that I found a round metal clip in the oil pan. The only place I can think where it may have come from is around the distributor shaft. It was not distorted or cut up so apparently it has done no damage. This might be a safety item that all Corvair builders should look at on how to prevent. If that piece lodged in the distributor gear, it would certainly bring you out of the air. Thanks,

Ray Simpkins, Piketon, OH, Manual #5389
Reply from WW:
Corvair heads are cheap and plentiful enough that I'd advise you to simply find another matching head. It need not have identical numbers. Just keep 110 heads with each other, and 95 heads with each other. And of course, you'll need to ensure you have a 1964 or 1965-69 cylinder head, whichever your cylinders require. While I'm sure the right welder could weld up the combustion chamber, I myself have found it difficult to do welded repairs in the combustion chamber because of the extreme difficulty cleaning the aluminum of contaminants. I restrict our welding on heads to intake pipes and cylinder fin repair. In both these cases, we're working from clean, machined surfaces, which weld nicely. It's hard to imagine a good repair costing less than another core cylinder head. Perhaps one of your other engines has better heads.

The clip down the distributor hole, if it's basically a washer with two bent corners, is part of the distributor hold down clamp. People did occasionally drop these down the hole and not bother to fish them out with a magnet. You're right that you cannot tolerate any type of fastener dropped into the motor at all. There are round, machine shims on the distributor shaft, but I've never seen a broken one in the hundreds of distributors we've handled.

Subj: Open
Date: 12/20/04

Hi William. Finished my RV9A tail, soon to be for sale. I picked up a great Corvair engine last week. New plan is to build a 601XL.

Steve Gordon, Cincinnati, Ohio, Manual #6267

Reply from WW:
An RV-9 is certainly a good aircraft, but the 601 fills the bill for many people. Beyond being a candidate for a Corvair engine, which the RV9 is not, the 601 is much faster to build, perhaps taking only a third the time. My EAA chapter, 288, has an extraordinary following of RVs, and many of these people studied our 601 closely when we first picked it up. Most of them were very impressed that we completed and flew the airplane in a fraction of a year, something anyone would be very hard presssed to do with an RV.

Subj: Open
Date: 12/21/04

Just purchased an "RD" engine this weekend. It's being torn down and inspected after the first of the year.

Robert Johnsen, Nampa, Idaho (Canyon County), Zenith 601XL, Manual #6434

Reply from WW:
Congratulations on your find. An RD is a very common Corvair, and an excellent candidate for conversion. The first Corvair I owned was a 1967 coupe. I drove it for many years as my only car. This included trips to California through Death Valley, as well as throughout the northeast. This car was equipped with an RD engine. When the body finally gave its last full measure, I saved the engine to rebuild it for something special. Today, this exact engine case is the one that is in our 601. I'm sure your engine will provide you with as many enjoyable adventures.

Subj: 601 Performance
Date: 12/20/04

Thank you for opening up the Q&A again. This is a welcome addition.

Im still very curious what real performance numbers as far as cruise and WOT you are getting on your Corvair powered 601XL. Ive shied away from building the 601XL mostly because of the historic lack of accurate performance numbers from the Zenith Web site, and Ive been anxiously awaiting your figures because I know they will be the most accurate available with probably the cleanest build out there. I have a hard time taking the Zenith published numbers to heart, since Ive read many a posting from 601HD builders claiming only 85knots max cruise, while the Zenith Web site shows it should cruise at 120mph.

Im still exploring my options between building a Sonex and building a 601XL. Id like to power my plane with a Corvair, but I consider the Sonex a less than proven candidate for Corvair power based on only the 1 example flying and, of course, your lengthy advice on the subject, Id likely choose something else for the Sonex. Unless I see that someone is getting decent speed from the 601XL, it would be a tough choice to make.

So, have you done triangulated speed tests on the 601 Vair??? If so can you publish the results here?? Are you waiting for some modifications first???

Thanks, Bruce Johnson, San Antonio, TX

Reply from WW:
The last aerodynamic modifications I want to make to the 601 are coming together. I stil want to get wheelpants and gearleg fairings on it, and we're contemplating a smaller tailwheel. From previous experience, I suspect there's 8 or 9 mph in these changes. We flew the 601 this morning (Dec. 22) for the first time with the smaller 15x600x6 tires. The plane picked up 4 mph. We chose these because they'll fit inside RV-8 wheelpants. We changed the landing gear leg last week, and prior to this, I didn't want to build gear leg fairings for a gear we were planning on changing. The plane flew at 133-134 mph indicated at 24" of MAP and 3000rpm. This is a cruise power setting that burns about 5gph. Top speed is about 10 mph faster. I hope to have the gear legs faired and the wheel pants on by mid January. While our cowl may be slightly more streamlined, our airplane is about the same level of finish as the factory plane. I actually think the smaller wheels and fairings would make the tricycle gear model slightly faster on the same engine.

Our intention is to finish the mods and let everybody know where it stands. We're very happy with the way the plane flys. We're going to run the plane in the Sun 100 Air Race (a triangular 100 mile course) this coming April at Sun 'N Fun. The published results of the race end all debate of what particular aircraft are capable of. You can look up past results in old copies of Sport Aviation. Some kit planes noted for high speeds in brochures are noticably absent from the stats. For example, Europa Aircraft, which claims 200mph capability, have to my knowledge never run the race. They could hardly claim it's inconvenient since they're based at the Sun 'N Fun airport. You can come to your own conclusions. Whatever our speed shows in the race, people will certainly know it's an honest number.

When comparing 601s, you've got to remember that an HD is a radically different wing than an XL. Even the HDS, billed as a faster wing than an HD, is not as aerodynamic as the XL. As a side benefit, the XL with flaps lands slower than either the HD or HDS. I too read reports of HDs that cruised below factory advertised numbers. However, many of these reports failed to include details about whether the plane was plans built or built from a kit, what kind of engine and how healthy it was, whether it had a good prop or a homemade one, and what kind of cowling, wheelpants and leg fairings it had. With these points in mind, I don't think that the factory published numbers are that far fetched. We've flown more than 25 people in our 601, and if you're in our area, we'll be glad to take you for a ride and demonstrate why we're enthusiastic about the design.

Subj: Accessory Case Oil Cover
Date: 12/2/04

Are you selling the cap-off piece for the old oil filter mount? I see I can get everything else needed to move the oil system and change to fuel pump design, but it sounds like the block off cap is critical, and I dont think I want to attempt it. Let me know if it is available and how much if it is.


John, State College, PA

Reply from WW:
Here's a link to a photo of the accessory case oil cover: Close up of Accessory Case Oil Cover. We sell this part fully machined and ready to bolt on for $69. This includes all the stainless hardware. Very shortly, we're going to offer completely rebuilt and tested accessory cases with this part already installed on an exchange basis for builders. For now, we'd be glad to sell you the part separately.

Subj: Rods
Date: 12/6/04

Where can I get balanced rods?

Jimmy, N.J.

Reply from WW:
All of the motors we rebuild in the shop for sale have a balanced, rebuilt set of rods with ARP bolts already installed. We get these from Clarks Corvair Parts Inc., 400 Mohawk Trail, Shelburne Falls, MA 01370, 413-625-9776. They are part number C9203WW, balanced connecting rod sets at $214, less the $42 that they give back when the cores are sent in. $172 is very inexpensive for quality work done right when you consider that the rod bolts are worth $75 themselves.

Subj: ACR44F
Date: 12/7/04

A very quick question. I purchased a set of NOS AC R44 SPARK plugs on eBay and have a green stripe on them. Apparently that have not been available for a long time. Can I use these in my Corvair engine? Your advice would be greatly appreciated.

Regards, Darren, VP-2, Australia
Reply from WW:
In the U.S., AC R44F plugs are readily available and in continuous production. The standard Corvair plug in the 1960s was the 44FF. This plug has not been produced in a long time. When we get a core motor in with an old set of these installed, you can be pretty sure it hasn't been driven in 20 years. We do all of our flying on R44F plugs. These are the resistor version of the 44F. Operationally, they run just the same and have provided us with years of good service.

Subj: 601XL FWF
Date: 12/8/04

I have a few questions about the Corvair engine. I'm looking at building a Zenith Zodiac XL. Do you guys sell motor mounts for the Zodiac? Also, as far as firewall fwd kits, do you sell those too?

Thanks, Jeremy
Reply from WW:
On our Products Page, you can see that we sell 601 Motor Mounts, Nosebowls and many other parts to mate the Corvair engine to the 601 series of aircraft. These are very popular items, and more than half the motor mounts we make these days are going to 601XL customers. We are expanding our catalog of parts to simplify the 601 installation. Within a few months, we'll have every single nut, bolt and screw available. But right now, our 601 customers are well served by our manufacturing all the difficult to make components like the nosebowl, mount, etc.

As for the engine itself, we produce a steady flow of completed engines like the one posted at our Engine For Sale page. The majority of our customers build from our plans and components, but this engine is appropriate for those who wish to purchase an engine ready to install.

Subj: Wag Aero Planes
Date: 12/10/04

I am going to order the plans for a (J-3 Cub) Sport Trainer or a Super Sport Trainer. I have a Corvair engine with the correct numbers and will be ordering your Manual soon. I was wondering if you sell a motor mount for this type of aircraft? Also, in your opinion, which aircraft would be better for myself (6'3" @245lb) and the Corvair engine?

Thanks for your input, Mike
Reply from WW:
A standard Corvair engine will be a good powerplant for any of the J-3 series aircraft, like the Sport Trainer. Keep in mind that the J-3s flew on engines from 37 to 65hp, and the Super Cubs, which are the same size airplane, flew on 100-150hp. A J-3 is not a large aircraft inside, but its layout is more friendly to taller pilots than many of the J-3s contemporaries, like the Taylorcraft. It's a simple matter to check the fit out at an airport that has a J-3 available for you to sit in. The popularity of the J-3 means that you won't have to drive far. I took a quick look at the Wag Aero Web site and couldn't find a reference to the Super Sport. Perhaps this is something new? Wag Aero is a very reputable company and their plans are very good.

Subj: Cleaning
Date: 11/24/04

I also have a question about cleaning up the heads and case. I have been soaking them (the heads) in my cold bath parts washer with solvent and they still are not coming clean. I have been using an old tooth brush to scrub them. I see that you mention in your write up about CC#8 that you have a blasting booth with wallnut shells. Is that the way to go, or a Dremel tool with a wire brush? Thanks for any ideas and keep up the great work on the Corvair.

Doug, Winnipeg, Manitoba, Canada
Reply from WW:
Yes, we use the walnut shell blaster for anything that is made of soft metal or going to be inside the engine, or subjected to oil flow. Walnuts or plastic media will go a long way to clean up cylinder heads. We rarely have to clean them up all the way ourselves, as we have a machine shop in our area which does valve jobs for us, and they take care of the cleaning at that time. We just remove most of the grease as a courtesy, to stay on their good side. Our walnut blaster does most of its work cleaning cases and the inside of accessory case covers.

Subj: Corvair Fuel Pump Orientation
Date: 12/1/04

Saw the pics of CC#8 and they were just great! I really wish Judy & I could have attended but we were in the midst of a move from Raleigh NC to our new home in Oriental. We are just about to get all the stuff out of the boxes & put away so its time to return to construction of the Corvair. We have ordered a full 601 XL kit from ZAC since we last saw you at Oshkosh and plan to pick it up in Feb.

My question involves the Corvair fuel pump. I was looking at possible ways of routing the fuel lines from the fuel pump to the MA3-SPA carb and it suddenly dawned on me that if the pump was rotated 180 degrees the line connections to the carb and gas collator would be both more direct and also further away from the hot engine block. Since the pump is push rod actuated and secured with a single tapered bolt, it should be a simple matter to redrill the pump body to effect the reversed mounting orientation. Have you ever considered doing this? Your comments would be appreciated.

We hope to be able to attend your next CC event. I continue to ever more impressed with the scope and quality of the work you are doing to make the corvair into a safe affordable aviation engine. Your grassroots approach to homebuilding is all too rare these days. Thanks for all you do.

George, 601, North Carolina
Reply from WW:
Great to hear from you. You should check out all the 601 updates at www.flycorvair.com/601.html. We have updated the 601 fuel system to a far simpler configuration using two electric fuel pumps in series. We no longer have the mechanical fuel pump installed in our aircraft. Although you're correct about the stock mechanical pump being pushrod activated, the housing is asymmetrical and has an internal boss for the mounting bolt which prevents it from being rotated as you suggested. I know this in detail because we considered the same idea at one point. The installation with electric pumps now has about 50 flight hours on it, and I'm happy with it. It's an easy one for builders to replicate. When you head over to the Zenith Factory, say hello for us.

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