Strike two :(

[jwd3ca]

Yeah, Larry, I get it, not my first rodeo, been building engines, cars, motorcycles most of my life, and recently (last 15 years), three experimental aircraft. But sub-standard spark plug threads was about the last thing I expected to run across. I'll get through this, albeit with a considerable time set-back. Just disappointed, that's all.

And I'm not sure I agree with your opinion of heli-coils being bandages, vwglenn. Have you had bad experiences with them? I'd sooner believe that they would be a lot more robust than plug holes badly threaded into aluminum . And who's to say the replacement heads will be necessarily better?

[13brv3]

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

Hi Larry,

This will be my 6th experimental aircraft, and one of them had a Mazda rotary engine, so I'm used to wild and woolly :mrgreen:

Cheers,
Rusty

[Rynoth]

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.

For what it's worth, I've had better success using email versus phone with tech support concerns, I've even received prompt responses on a Saturday (though probably not the norm.) tech@aeroconversions.com

[jwd3ca]

Follow up: Sonex is aware of this sub-standard plug hole machining in a particular range of cylinder heads (lucky me!). Apparently 'worn out' tooling when they changed over to Mofoco. I was given a choice of returning both my heads for replacement heads or installing Time-serts and being credited for my $$ outlay. I've decided to go with the Time-serts option, doing all 8 plugs. I'm confident that the Time-serts will be a significant modification/improvement to the aluminum heads. Opinions?

[gammaxy]

I have the pre-mofoco heads and they seem to have good threads. Due to warnings about possibly stripping out the threads, I have only performed a compression check with the heads cool. If the Time-serts reduce worry about stripping out the threads, they are probably a plus.

[jwd3ca]

As promised, here is a link to the TIME-SERT installation article (photo-documentary, really) I submitted to EAA's Bits & Pieces:

http://tinyurl.com/pof33g3

To their credit, Sonex did credit me with the cost of the TIME-SERT tooling and inserts needed to repair the heads. I only wish that they had pro-actively notified me months ago that my particular heads might have a problem due to known 'worn tooling' at Mofoco for a certain range of serial numbers :( I'm not sure what that exact range is, but my s.n. is 0818.

[Rynoth]

... 'worn tooling' at Mofoco for a certain range of serial numbers ... I'm not sure what that exact range is, but my s.n. is 0818.

My s.n. is 812 and I had to have them replace a head due to stripped plug. This was about 4 months after initially delivery of my kit, so hopefully the newer head was made better.

[vigilant104]

I'm confident that the Time-serts will be a significant modification/improvement to the aluminum heads. Opinions?

The Time-serts are supposed to be a significant improvement over helicoils. They are solid and provide good, hard threads that are much less likely to strip out than the stock threads in the AL head. Some VW racers put the Time-serts in when the engine is new just for this reason, and it might be something those running VW engines in their airplanes consider doing, too. With twice as many plugs per cyl (= more opportunities to have a problem), with the lower one a bit hard to get to/thread straight, and with frequent plug changes/inspections,compression checks, etc, these plug holes get a lot more wear than they might in a car.

[jwd3ca]

I agree, which is why I opted not to exchange my heads for new ones. The TIME-SERTS look like they are extremely robust and I'm happy with my decision. That said, if one had to spring for the tool(s), it does represent a significant expense (~ $150 USD for the 12 x 1.25).The inserts themselves are negligible, < $2 each.

[Bryan Cotton]

jwd3ca,
Good writeup, thanks! Did you buy or rent the tools?