How perfect do main bearings need to be?

[Spaceman]

I got my Aerovee kit recently, but the crankshaft was backordered. I got the crankshaft in a separate box last week, along with the main bearings. Unfortunately the split bearing appeared to have bounced around the box quite a bit and one half put a pretty big gouge in the other (see attached picture).

I emailed Sonex and they were quick to send me a new split bearing. I got it today and it was really well packaged, except both halves of this one also have little scratches! One is really obvious (top one), and the other one is not too crazy but you can definitely feel it if you run a finger over it carefully (bottom one). I'll attach a picture of this pair in the next post.

Is this acceptable? In my limited engine building experience prior to this I always thought bearing surfaces should be pretty much perfect. However I've seen how the stock VW silverline bearings are packaged and they're just loose in a little box, so the split bearing halves are free to clank into each other. Is there a tolerance or should I send all these dang bearings back?

[Spaceman]

Here's the second picture I was referring to. This is the replacement pair I got today.

[sonex1566]

Hi Chris,
I feel your pain! Luckily for me I have never had to 'make do' with a set of bearings in an engine except a heap of crap lawn mower engine many years ago. I think that if I was in your position and used the bearings I would forever have that feeling of doubt over the reliability of my engine. I know it's only an aircraft engine, nothing to worry about, right! I reckon that if you attempted to clean up the nicks in the bearing surface you would risk doing more damage and then lessen your oil pressure to that journal. If you left it, the raised portion of the bearing would make that journal a bit tight. It just monumentally sucks that you need to reorder bearings....again. If it was possible to speak to a dune buggy person or airboat operator to find out their experiences regarding slightly dodgy spare parts supplies might make you feel better. Although, I still believe that I would choose to spend some more dollars and not worry about it in the future.

[Area 51%]

Throw them out.
I purchased no less than 3 sets of bearings before I got a complete set without gouges or other flaws.

I just happen to have an extra pair of the bearings you need. P.M. me your address and I'll get them to you.

[Spaceman]

I emailed that pic to Sonex last night and Kerry already replied back saying not to use them. They're going to send me another bearing! I just couldn't tell if I was being overly picky, unlucky, or if this was normal for VW bearings. I guess I was just unlucky to get two bad ones in a row.

I agree with you Richard, I'm sure if I used the best two halves that I have the engine would run, but I'd always wonder what condition the crank was in. Not worth it!

Thanks for the offer Area51%!!! I'll see what shows up from the factory this time since I think they're already getting it on the way. Hopefully that'll be the last one......

[NWade]

Chris -

Good on you for being careful! You should be sure to inspect every part in your AeroVee kit. A lot of us have found bad parts, or parts that didn't match up with what was in the instruction manual.
Usually the cause is a supplier to Sonex has either had a bad batch that snuck through that 3rd parties' QC, or they changed parts without telling Sonex staff, or the part was incorrectly packaged when it was sent to Sonex. I wish Sonex had better protocols (or manpower) when it comes to inspecting these items; but it seems to me that they get boxes/pallets of engine components in from 3rd parties, and just ship 'em out to customers without opening them.
Sonex airframe parts have always been of top quality and definitely well-checked and well-packaged before being shipped to me. Sadly the same level of attention-to-detail doesn't exist for the AeroConversions line of products.
It puts all of the onus on us customers to thoroughly check every item, and not accept parts as "OK" blindly. Sonex has always been reasonable with me about replacing parts (although I've occasionally had to nudge them or provide additional data to show why the item is a legitimate concern); but its happened enough that several folks here (including me) have some pent up frustration over it.

Keep that critical eye on your parts quality and follow the AeroVee assembly manual & videos, and you'll have a good engine you can be proud of in the end!

--Noel
Sonex #1339
AeroVee Turbo
(not quite flying, but a few hours of ground-run time already)

[Spaceman]

Thanks for the tips guys! The new bearing showed up today in perfect shape. Got the crankshaft installed and case closed up with everything looking good as far as I can tell. Finally some progress!!