SonexBuilders.net

I have been going through the WW conversion manual and thought others might be interest in the costs I'm finding to build up a Corvair motor. I'm not sure how to post it as a list so it is more readable but the details are at the bottom of the post. Total came to $7366 for a 2700 motor. The only thing I haven't accounted for is the cost to bore the cylinders oversize and to do a valve job on the heads. I have a few friends with the equipment that can help me get that done. On top of the $7366 number to get flying you will need:

Intake - I plan to fabricate my own. Estimate $100 in materials
Exhaust - Same as the intake. Make it myself from $100 in materials
Carb - Haven't decided on which carb yet but $600 would be reasonable for a rebuilt MA3-SPA
Prop - Probably will go with a Prince or Senesenich. Cost will be $1000-$1500
Spinner - Depends on the prop I choose but many use the vans spinner for $220
Cowl - The fiberglass nose cone is available for around $350 if I decide to not try my hand at fiberglass
Baffles - I can make my own out of some scrap aluminum sheet I have left over from building the plane
Engine Mount - I plan to fabricate my own as it is a simple bed mount. Figure $100 in materials

I'm sure I am missing a few small things but it seems like 10k is a reasonable number to build and install a 2700 cc corvair on a sonex airframe. To step up to a 3000 cc motor the cost goes up another $3000. That is mostly due to having to buy custom pistons, cylinders, rings, crank and connecting rods from WW or Fly SPA. In addition to the parts you will also have to send your case and heads out to be machined to make the bigger cylinders fit. The other parts that I said I would fabricate above are also available finished and ready to use from the Fly SPA website. They just cost more money.

Other places that you may be able to save money is the lightweight starter package. It adds $770 to the cost. There are conversions using rebuilt Subaru starter motors that can be done for around $200 but is significantly heavier and not as clean of an install. The same for the oil pan. Cost of the billet pan is $320 plus another $65 to install it. You can modify the existing pan and pickup tube for free if you are comfortable doing the welding needed.

Keith
#554



Description Source Part Number Cost
Crank Processing & Fifth Bearing Fly SPA NA $2,350.00
OT-10 Cam Clarks C8800R $197.00
Cam Key Clarks C5858 $1.60
Cam Thrust Washer Re-use NA NA
Cam Gear Clarks C783X $43.50
Case Nuts and Bolts Re-use NA NA
2700 Pistons Clarks C3901+60 $372.00
Rings Clarks C7492+60 $128.55
Connecting Rods Clarks C9203 $293.00
Cylinder Bore Gasket Clarks C1180 $45.90
Head Gasket Clarks C3946 $33.30
Cylinder Bore Service TBD NA NA
Head Valve Job TBD NA NA
Valve Springs Clarks C1386XA $40.30
Intake Valves Clarks C3020P $48.00
Exhast Valves Clarks C124RP $118.20
Pushrods Reuse NA NA
Push Rod Tubes Reuse NA NA
Rocker Arms Reuse NA NA
Rocker Balls Clarks C2303 $21.80
Engine Baffles Reuse NA NA
Valve Covers (modify on own) Reuse Na NA
Valve Cover Gaskets Clarks C3018 $8.00
Rear Oil Seal Clarks C483V $9.75
Rear Case to Block Gasket Clarks C4825 $4.70
High Volume Oil Pump Clarks C3942 $122.95
Oil Pressure Regulator Piston Reuse NA NA
Oil Pressure Regualtor Spring Reuse NA NA
Harmonic Balancer Dale Mfg NA $146.50
Gold Billet Oil Pan WW 2201B $319.00
Modified Oil Tube & Install Kit WW ?? $65.00
Front Cover NA NA NA
Starter WW 2400L $769.00
Top Cover Gasket Clarks C481 $5.15
Short Gold Prop Hub WW 2501B $635.00
Hybrid Studes WW 2502 $89.00
Safety Shaft WW 2503 $89.00
Reverse Gold Oil Filter WW 2601 $265.00
Oil Filter Amazon KN HP1008 $9.98
Oil Cooler Reuse NA NA
Oil Cooler Mount Gasket Clarks C680 $1.85
Oil Cooler O-Rings Clarks C123C $4.15
Rear Alternator Fly SPA NA $375.00
Dual Ignition Distributor WW 3301 $385.00
Spark Plug Wires Amazon Accel 5041 $53.95
Spark Plugs Amazon Denso IWF16 $48.00
Ignition Coils Amazon Bosch 0012 $45.00
Condensor Napa RR-176 $6.56
HT Switch Unit Amazon MSD8210 $80.32
Tach Pickup WW 3411 $70.00
PMOV B&C NA $65.00
Total $7,366.01

This is a pretty good start. I think you are starting to see that the $5-7k Corvair is becoming a thing of the past. I don't think this is a bad thing, because it has corresponded to increases in quality and reliability from using greater numbers of new parts in the engine.

The heads can be redone by SPA, which is the highest cost, but they really know what they are doing. This service costs $2K. William definitely would not endorse going to a local guy to do this job.

https://flycorvair.net/2015/08/24/sourc ... ad-source/

Your estimate includes you doing a fair amount of the work, including welding - which is great, I just don't have those skills. You'll certainly want to be confident in your skills if you'll be doing the mount.

As I said, I've got a lot of $$$ in mine; it's a no-expense spared Corvair. But I believe William is right that if you are going to save $$ on your homebuilt engine, but then put in a fancy glass panel, it's a fool's errand.

Good luck; I've yet to fly but have loved the build process for the Corvair.

I don't think there was ever a time you could build a reliable and light corvair for 5k. The early days were filled with broken cranks, heavy starters and alternators, and a lot of custom machine work. There have been a lot of improvements since then.

I'm not clear exactly why the high cost of rebuilding the heads. I included all new valves in my cost estimate. The only thing left on the heads is to flycut the mating surface if it isn't flat and replace valve stem guides and valve seats if they are worn. The guides usually aren't worn on these motors and seats can usually be recut or lapped if they aren't loose It's a fair amount of work to redo everything but not $800 a head worth and not something that just about any automotive machine shop can't handle. The crank is another story. If I don't go with the wessman crank I plan on spending the money and letting him do the grinding, nitrating, magnafluxing, etc. It's not a place to cut corners.

No fancy panel on my plane. I have a used mgl ultra that I bought for a few hundred dollars.

Keith
#554

Thanks!

Great list of parts - I am working up a similar spreadsheet of parts and costs.

I was going down the WW Corvair path to power a Pietenpol.
Got at workable core w/heads for $200. Bought the manual at OSH.
A few more parts online like a cooler and back plate.
I then realized I was going to be into this about $10K by the time I had the engine I wanted with all the new parts from SPA and WW.
Put the Piet on hold and sold the core for $350 to a Panther builder.
If you are good at scrounging parts, you might be able to build one for under $7k.
I don't think its a bad engine, but to do it right isn't a "cheap" way to power an aircraft.

Have you priced the parts to put together an aerovee fwf package lately? It isn't exactly a cheap motor anymore either. I was shocked to see that just the aerovee mount is now almost $2000. I'm not going with the corvair because I think it will be a cheap solution. I'm going with it because I think it will be a more reliable 100hp motor than the 80hp stock or 100 hp turbo aerovee is.

Keith
#554

kmacht wrote:Have you priced the parts to put together an aerovee fwf package lately? It isn't exactly a cheap motor anymore either. I was shocked to see that just the aerovee mount is now almost $2000. I'm not going with the corvair because I think it will be a cheap solution. I'm going with it because I think it will be a more reliable 100hp motor than the 80hp stock or 100 hp turbo aerovee is.

Keith
#554

No. But considering all mounts are almost $2000 now, isn't every engine option equal when considering that?

The corvair mount for the sonex from SPA is $1200 but that wasn't the point. I was just using the mount as an example. Years ago the sonex mount was $1000 and the engine was $5995. The point is that all engine costs have gone up. There are no longer people doing corvair fwf for $6000 cjust like there is no longer a $6000 vw fwf package.

Keith
#554

kmacht wrote:The corvair mount for the sonex from SPA is $1200 but that wasn't the point. I was just using the mount as an example. Years ago the sonex mount was $1000 and the engine was $5995. The point is that all engine costs have gone up. There are no longer people doing corvair fwf for $6000 cjust like there is no longer a $6000 vw fwf package.

Keith
#554

Agreed. Now the amateur built engines are approaching what a factory jab is.

There are a lot of apples-to-oranges comparison, but for me, the big picture is this:

I'll have about $15k in my FWF for the 3000cc Corvair, including mount/carb/etc. That includes every part available by WW/SPA including mount. A new Jab 3300 is $19k, and I already have the FWF with my Sonex kit. So there is some savings, but not a ton.

It's not the cheap route by any means. But I wanted the experience of building my own engine, greater HP, and more guidance as a first time builder than I could get with the Aerovee. The Corvair fit all of these items, at a cost that is between an AV and a Jab.