Loose exhaust stud on O-320 E2D

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7 months 1 week ago #3251 by TOM BRAEUNIG
Replied by TOM BRAEUNIG on topic Loose exhaust stud on O-320 E2D
Hi Steve,

I got the heli-coil installed today. I put everything back together and torqued the exhaust nuts to the specified torque, no problem
The stud hole was pretty worn. I was able to slide any of the "oversize studs" up into the hole and barely catch a thread. I was going to drill the hole out to 21/64 per the heli-coil installation instructions, but I thought I would try just the heli-coil tap first. It worked fine. I was able to tap the hole without drilling it out to the larger size. The helicoil threaded in fine and I installed my standard size stud. It was a good fit.



Thanks for your help.

Tom

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7 months 2 weeks ago #3237 by TOM BRAEUNIG
Replied by TOM BRAEUNIG on topic Loose exhaust stud on O-320 E2D
Hi Steve,
Here's the answer I got from Lycoming. I'm still baffled as to what the oversize really means. Russell recommended that I use a heli-coil if the threads are worn out or gone. In that case, I would think that the heli-coil would take me back to the standard size stud. (so what's the purpose of the oversize stud?)
I've also sent my info to McFarlane, and I'm waiting for their take on it.
I could sent you the full email from Lycoming, complete with pictures.

Hello Tom,

The oversize of the studs refers to the pitch diameter not the outside diameter of the threads. Attached you will find the excerpt from the engineering drawing for those studs. The drawing lists the oversize pitch diameters and there are a few pictures about thread pitch which I hope will help.

If you have any question feel free to ask.



Best Regards

Russel Gait

Field Service Technical Representative

Lycoming Engines, an Operating Division of Avco Corporation

Phone #: 570-327-7198

Email:

www.lycoming.com
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7 months 2 weeks ago #3234 by TOM BRAEUNIG
Replied by TOM BRAEUNIG on topic Loose exhaust stud on O-320 E2D
Will do, thanks
Tom

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7 months 2 weeks ago #3232 by STEVE ELLS
Replied by STEVE ELLS on topic Loose exhaust stud on O-320 E2D
Hi Tom;

Based on everything you've told me, it seems to me as though you got some bogus parts.

I recommend that you tell Lycoming about this malfunction.

Keep me in the loop about the MacFarlane studs.

Thanks

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7 months 2 weeks ago #3229 by TOM BRAEUNIG
Replied by TOM BRAEUNIG on topic Loose exhaust stud on O-320 E2D
Hi Steve,

I measured both ends of the studs, and they are the same diameter.(within .001") and the exhaust nut fits all 4 studs.

Here's a better set of pictures to illustrate the problem: (I sprung for a nice digital calipers)

You can see the oversize dimension stamped on the end of the stud. The one with no number stamp is the standard replacement stud.
You can see that all 4 studs are about the same diameter as measured with the caliper. Nowhere near the +.003" , .007" or .012" that I would expect to see.

I keep thinking I'm missing something here, but I fully expected to see the oversize studs mic out at about .313" , .317" and .322" (based on the measurement of the standard stud)

I've requested an RMA from Airpower to return the studs. I'm still thinking this is a manufacturing defect. (Mislabeling standard size studs as oversize). I'd like to have Lycoming confirm this.

In the meantime, I found that McFarlane has their own equivalent exhaust studs with the same oversizes. I've emailed them to ask the exact diameter specs on the oversize studs.
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7 months 2 weeks ago #3227 by STEVE ELLS
Replied by STEVE ELLS on topic Loose exhaust stud on O-320 E2D
Hi Tom;

I suggest you measure the other end of each stud to see if there's dimensional differences there.

If the OS studs won't work, I think you should look into the installation of a "key locking" insert instead of a Heli-coil.

There's information for the Acme Key locking inserts here: acmeindustrial.com/keylocking-threaded-inserts-2/ .

Another brand is the Keensert key locking inserts.

Please let me know what you find

Thanks

Steve

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