Hello All

I only know of 3 current shops for the 5th bearing ...let me know if I'm missing anyone

William Wynne/SPA

Azalea Aviation

and Roy of Roy's Garage

Has Roy gone out of business? The web site I had appears to no longer work

we all love and promote the specific one we choose over the others, I understand that.

I have yet to choose..... I am not looking for specific recommendations but  more interested in the differences in how things are done between the different suppliers, technically or mechanically etc

If they all work equally well then it gets down to who is easier to work with, delivery time, and of course price

Just looking for some info to make a decision

thanks for any input


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I am surprised that no one has offered there opinion on this yet as it is usually a somewhat hot topic with people having a very definite opinion on which is best so I will share what I THINK I know. I have not seen any of the three designs in person, I have spoken to William on the phone several years ago and had e-mail contact with Dan (SPA) during that same time period. I am working on my 5th bearing which is similar to the SPA bearing (hopefully sucessfully) which is for my own use and will not be offered for sale so I have nothing to gain from recommending any particular bearing.

As we know there is not a good relationship between the three producers of the available bearings and some are more vocal than others which is a turn off for many. The first on your list has been around the longest and has provided the most available documentation for the corvair, product availability and delivery times have been poor for long periods, I think this has been largley cured with business maturity and stock and delivery control being handled by SPA. Dan's fifth bearing, (especially the gen 1) I think is more in line visually with the corvair look. I know little about the second suppliers bearing, Some swear by it but it has had a bad reputation (deserved or not) in running it's business. (businesses) The bearing they produce looks very aerospace-ish and I see no reason it would not work well. The third supplier has always apparently had long delivery times as each was individually machined. 

For me if I was buying I would still choose the first supplier as I have been provided with the most info on the corvair thru build manuals and dvd's which guided me in the direction I needed to go and the original fifth bearing could be installed by me in the field.With the gen 2 bearing the playing field is somewhat more level between the first and second suppliers as I beleive both of those products have to be installed by the manufacturers. The third I never considered because of the delivery times. All things considered and personalities aside I still think that WW and SPA provides the most information and support for the corvair. Haven't looked at cost lately so I have no comparison there.

Hello Dan

Thanks for your reply and in sites !

I agree I was expecting this to run away from my intentions, which is just to be a question on the merits of the mechanical systems of the various styles and why, and not get into the personalities involved.

some of that other stuff might be involved in the ultimate decision..just trying to keep it on the technical merits of each style



I think an important aspect of deciding should be actual performance of the various products. You say, "If they all work equally well then it gets down to who is easier to work with,..." You should inform yourself if they do in fact all work equally well. While informing yourself make sure that you are comparing "apples to apples". Any installation where the installer did not do so in compliance with the manufacturer's instructions should be disregarded. Yes, this is experimental aviation and you are free to do as you wish but, any deviation from a standard installation may have effects that may not exist otherwise and change the products reliability. Do your homework. Look for those that have installed the products. Talk to them if able. Go to a workshop that WW and Azalea give. There you will be able to get "hands on" with the product.

I have done some of these things myself. I have attended one of WW "Corvair Colleges". Also watched as engines were assembled and run at two of Zenith's gatherings they have in September. There were parts on display and available to be handled and inspected. Dan and WW were there and answering any and all questions. There were planes with corvair engines there and their owners were there and glad to answer questions. Some of these owner/operators have a decent number of hours on the product. In fact, at the Corvair College I attended one of the owners gave me a ride in their plane.

I have not attended any of Azalea's workshops. I have explored their website and watch their Facebook page, but that only serves to briefly familiarize me with their product. From what I see they seem to be making inroads in this market and increasing their number of installations.

I know almost nothing about Roy's product.

The gist of what I am getting is, reliability, this should be your prime motivator as to which way to go. Opinions, personalities, product aesthetics and any other aspect that doesn't have anything to do with whether or not the engine keeps running means little. The only way for YOU to know this is for YOU to find it out.

Good luck.

Keep building.


Hello Ernie

thanks for your input....


Hi John,

I tend to go with what has the longest proven track record.  I believe the majority of flying corvairs with fifth bearings are using the SPA version.  I have the SPA Fifth bearing on my corvair and have had zero issues with it.  I started with a 2.7L corvair and then upgraded to a 3.3L corvair.  I used the same bearing housing for my new build after SPA replaced the bearing shells and the bearing itself.  I was amazed with how little wear the original bearing had after 502 hours in my 2.7L corvair.  I now have 160 trouble free hours on my 3.3L.  Mind you that I don't baby my corvair. I often joke that I only have two throttle settings on my corvair...idle and wide open.  The funny part is its not a joke...once the throttle goes to WOT for takeoff  that's where it stays until I throttle back for landing! 

Anyway, I've heard the spiel about why the other two bearing designs available are better and why some people go with them.  I don't have the qualifications to prove or disprove their claims, but I can say that for such a simple and elegant design the SPA bearing simply works and works well.  Maybe getting the case, crank, and fifth bearing all aligned to within a micron  or nanometer of each other is important.  Maybe having the thrust bearing surface moved to the front of the engine is better. I don't know, but after 660 plus hours of operating my corvair it looks like thousandths of an inch and stock thrust bearing surface works pretty darn good, too.

The features that attracted me to the SPA design are it's simple straightforward installation, the entire installation can be done by me without having to go through the time and expense of sending my case to be modified, the price is more than reasonable for what you get, and the manufacturers support is top notch. 

Good luck and happy building,


Late to the party on this. I've had my engine/components with Roy for the past 3.5 years. This is totally voluntary on my part. He's getting to the work as he has time, and I'm paying him incrementally. I have components from FlyCorvair that are older versions of what are sold now. I need some custom machining because of it, or I have to re-buy parts I already own just to get the current version.

I spoke to him today, and he's still in business. The website needs some overhauls, which is why it's offline right now. 

There are lots of reasons why I chose Roy's design, but it also helps that he is only a 1.25-hour drive from my house. Since I'm scratch-building and I'm nowhere near being done, I'm not in a hurry to get my engine. Roy is a one-man-band, so lead times can be fairly long depending on what you need. But he's been a great guy for me to worth with.

I had trouble for years with FlyCorvair in terms of getting the stuff I ordered. I started sourcing parts in 2004. Lead times for a single part was terrible in some cases but not others, but those issues seem to largely be remedied now. My own finances were why it took me this long to get close to having a finished engine.

There's been some drama over the years between the different suppliers, with one being much more vocal than the others. All 3 of the 5th bearing designs have pros and cons. Roy's bearing must be installed by him. It is align-bored to your specific case, so it's not a bolt-on assembly like the Dan bearing. Therefore you have to ship him your case (or source one from him). His number is 517-610-2307.

Hello Greg

thanks for your input. Without using the personalities involved as a criteria on their products...for now I am interested in the pros and cons of the various 5th bearing designs

It appears both Roy's and Azalea's are line bored and matched to the case...and SPA is a bolt on 

I would be interested in hearing your opinion of the various 5th bearing pros and cons on its merits and quality and components



I am going to chime in here since Greg is a friend of mine I can argue? with his opinion and none of us are going to be offended. (Not really, but I think there is some clarification needed). I agree with everything Greg has said and I do think lead times from any supplier now is basically a non issue and all will vary depending on work load, backlog of orders, ect. the only thing I think that needs clarification or explanation is that Roys, and Azalea's are line bored where as SPA is not which might lead one to believe that the SPA bearing is inferior. As I understand it the first gen SPA (Dan Bearing) was a bolt on which I personally don't think makes it any better or worse than the others because the bearing was installed and then was drilled for alignment pins so if the proper installation was done you would acheive the same accuracy of a line bored bearing. As I understand it the current SPA bearing when fitted to a spa crank has the bearing journal integral with the crank shaft which was the bolt on part on the gen 1 bearing, then the bearing housing is again installed and alignment pins then machined to provide alignment. In my personal opinion this is going to give the same accuracy as a line bored bearing and one system functionally will be any better than the other. Once again I have no dog in this hunt as I am building my own which will be line bored. (when you see my boring setup you may think a bolt on is better) Dan.

Ha! You snuck this in as I was typing my latest reply!

Hi John,

I am by no means an expert on this, but I'll give you my take:

Azalea's design uses a new thrust bearing and doesn't rely on the Corvair's thrust bearing. It is line bored to the case. I have no direct experience with Bill Clapp (Azalea), and have not seen his product firsthand. From what I can tell from pictures and design notes, it largely does the same job as the others, just with Bill's approach on the thrust bearing. The prop hub becomes integrated to the bearing and crankshaft unit. You basically have to source your "short block" from Azalea (though he may accept cores), and build your engine up from there. I do not know what his lead times are, and I have no idea how many are flying. Because of the architecture of his bearing, you are limited to a rear alternator and rear starter.

Roy's Bearing retains the Corvair thrust bearing, but puts a large front bearing surface on the front of the engine to handle the propeller loads. It is also line bored to the case. It's a split design, so that you can still disassemble the case halves for bearing replacement on the 5th bearing and the mains. You send your cores to Roy (or buy directly from him), and he'll build up the "short block" with his bearing. The potential disadvantage to Roy's bearing is largely just lead time. The unit itself is superbly crafted, but it's a rather labor intensive process (hence, the lead time). Roy also rejects engine cases if they don't meet very strict tolerances.

William's own design is not in production. Dan's bearing is a bolt design that also uses the Corvair's stock thrust bearing. If you're doing a new engine build, the 2nd gen bearing is designed to be installed and ground with the crankshaft, and there's no runout adjustment to be made in the field as that's taken care of in the crankshaft service. The 1st gen bearing is basically a retrofit option if you already have a running engine. Neither Dan's nor Roy's bearing require an integrated prop hub...it is a separate thing, unlike Azalea's.

None of the options are cheap, and because of the differences of the way the "big 3" approach the problem, it's hard to compare apples to apples. Azalea's assembled short blocks range from $2800-$4000. Roy's bearing will cost you $2,000 or so installed, assuming you have the proper cores. Dan's bearing on a new build is $2350 + cores, but only a $1300 addition to a brand new billet crankshaft (instead of a stock core).

I figure in real world terms, any of the 3 options are going to cost you roughly $2000-$2500 for just the 5th bearing part of the equation, but the way they complete the engine build makes things hard to break down. Roy's bearing was the best for me for several reasons. At the time I committed to having the 5th bearing done, my financial situation was such that a "payment plan" worked best for me. I'm not in a hurry to get my engine done since I'm nowhere near having a complete airframe. Roy is also fairly local to me, so it's easy for me to get service/tech support from him as long as he's in business. I don't have to pay crating and shipping charges with Roy because I can just drive over there and pick up my engine (or drop it off).

There are more Dan bearings flying than any other bearing. I don't know of any failures of any of the "big 3" choices, though. As far as I understand Dan's design, you have to take the bearing housing off the case to be able to split the block, unlike the Azalea and Roy bearings. In practice, I don't know if that's a big issue or not. Roy's bearing housing is basically permanently fixed to the case halves. It becomes part of them, which is why the housing itself is a split design. Azalea's design seems to be similar, but incorporates a new thrust bearing at the front.

In real, practical terms, it's hard to say what the pros and cons truly are. Some people feel that Azalea's new thrust bearing design is stronger, and it allows for a slight propeller extension depending on the installation. Dan's bearing has the most examples flying and has the most "legacy" now. Some of the "pros" depend on how much of the engine you want to build yourself, how you want to source components and how long you want to wait. Roy's bearing will probably take the longest to get, but once installed, you build your engine up off the assembled block with 5th bearing, crank & bearings. Azalea's is the same way. You can certainly take them back apart down to components, too. Dan's bearing is more of a kit after the crankshaft mating and machining is done, but even that's a bit moot. Depending on your location, whether or not you have cores and how exactly you want to build your engine may make some or all of these issues relevant (or not at all).

FlyCorvair/SPA are basically the one-stop shop for the entire engine build and 5th bearing. You'll likely have the shortest wait time with them, especially if you go the "engine in a box" kit route. The Azalea engine is also it's own sort of package. Roy's bearing is designed to work with William Wynne's engine architecture, but William no longer promotes the design. As far as I know, Roy's bearing is still a "valid" option in William's conversion manual, but I don't know what kind of real world effect that would have on building your engine with FlyCorvair parts and getting tech support from them if you have a Roy bearing.

As far as whether line boring matters, I have no idea if that makes any real world difference. In theory, it's more "precise," but whether that has any meaningful impact on matters is another debate.

Thanks everyone...that's exactly what I was hoping to learn about the various types. I too am in the middle of my build and on some cold winter nights, when it takes too long to heat up the garage I start thinking about the engine. I'm trying not to get sidetracked to the motor when there's plenty of airplane to be finished 

Thanks for your thoughts and experiences



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