Strike two :(

[jwd3ca]

So today might have been 'first start' day for me and my Sonex/AeroVee. Not to be.
This is my typical spark plug insertion method:

1 - a dab of anti-seize compound
2 - finger start the plug for several turns
3 - using a long reach spark plug socket with a 3/8 extension, and finger power only, screw the plug in until it bottoms.
4 - torque it

Worked predictably well until I got to step 3 of #2 cylinder.

At this point, I can spin the plug ad infinitum (with my fingers). As though the machine shop that machined the heads used the wrong tap!
Withdrew the plug, no metal to speak of in the threads (in other words, NOT cross-threaded)

Well CRAP! After my failed sump screen rivet, I'm beginning to regret my decision to go with the AeroVee. To say that the quality control in lacking would be an understatement :( We'll see what Sonex has to say tomorrow...

[Rynoth]

I had the exact same issue with one of my spark plugs during engine assembly earlier this year, seemed to easily strip the threads the first time I inserted a plug into one of the holes. For me it was one of the top holes, the aftermarket bottom plug holes seem to have much deeper threads, was this the same for you?

Fortunately for me this was during assembly so I didn't have to take much apart. Aero conversions replaced the head, but I received no feedback as to why this happened.

Here's a link to my blog post detailing issues I faced regarding quality control issues with my Aerovee heads, including the spark plug hole.

http://www.rynoth.com/wordpress/waiex/2 ... ad-issues/

Long story short, both heads in my kit had defects and had to be replaced. I was extra careful to clean the spark plug threads on the replacement heads and did find what seemed to be residual aluminum in them from the tapping process, but I can't be sure.

[mike.smith]

4 - torque it

I would suggest you not torque the plugs. Just seat them firmly. I used the torque values at first and found them way too high for these heads AND for the plugs themselves. I actually snapped the head off a plug (so the threaded end was left in the engine head) before I got to the proper torque value. VW guys have generally said not to bother torquing or you're going to strip the threads in the heads, and make it difficult to get them out.

[jwd3ca]

Hi Mike... note that I didn't get to step 4 (torquing). The plug is spinning in the head with finger power only. Never even put the socket handle on, let alone attempted to torque it... Note: this is the upper left front plug.

[XenosN42]

I had the exact same problem with one of my AeroVee heads for my OneX. Sonex replaced the head very quickly. I have 19 hours on my AeroVee now and it is running extremely well.

-- Michael

[vwglenn]

QC issues are common for most VW parts. Thorough inspection is a must. All kinds of issues (usually minor and easily corrected) can be found. It's pretty common to find left over sand from the casting process in things like sumps and such. Doesn't really make the part bad all the time. Just something you would normally expect to be right.

I never torque the plugs in my VWs. A drop of anti seize and nice and snug. Never had one blow out or anything like that. Did have one where I cross threaded the plug on #3 but stopped before it got bad. Was able to clean the threads and ran it for another 50 thousand miles or so.

Don't give up on the VW. You'll get it right and it will be just fine. I've had the exact thought about the Jab (Why didn't I get an Aerovee?)

[jwd3ca]

Torquing is not the issue here. The depth of the spark plug hole threads is the issue. Sadly, I just had the exact same issue with the upper right rear plug. It's as if the bit used by the factory to drill the holes prior to tapping was too large. As a consequence, the threads are so shallow as to be almost non-existent. Sonex tech line is giving me the recorded 'after hours' message although it is 10:30 Central time on a Wednesday, so I haven't yet been able to talk to someone there. But it's clear that I will now have to take two steps back from being ready to start the engine, and disassemble both heads. For either RMA return to Sonex for replacements, or machining for heli-coils. Disappointing.

[13brv3]

Sorry to hear about the problems. As someone who is just about to jump into a Onex project, it doesn't give me a lot of confidence in the Aerovee.

Rusty

[LarryEWaiex121]

Rusty,

Get used to being the quality control guy. Its your hide on the line each and every time you bolt something on your plane.
Not trying to be a snob, but welcome to the wild and woolly world of experimental aviation:)

Larry
Waiex121YX

[vwglenn]

...or machining for heli-coils...

Not acceptable on new heads. Make them send you replacements. I personally wouldn't run a heli-coil on my bus let alone a plane. They're a bandage to get you home or until you can save the money to get a new head in my opinion. I've seen (and heard) them blow on several occasions.