Loose exhaust stud on O-320 E2D

  • TOM BRAEUNIG
  • TOM BRAEUNIG's Avatar Topic Author
  • Offline
  • Senior Boarder
  • Senior Boarder
More
4 months 2 weeks ago #3225 by TOM BRAEUNIG
Replied by TOM BRAEUNIG on topic Loose exhaust stud on O-320 E2D
Hi Steve,

Well I got my 3 "oversize" studs from Airpower. I tried all 3 and none of them will tighten up. (I measured them them with my calipers, and they all appear to be the same size)
I miked them and found that they are all with in .0015" of each other, and actually just slightly smaller in diameter than the standard stud. I'm making my measurements on the longer threaded portion which would thread into the head.)
I talked to Airpower, and he directed me to Lycoming support. The rep that I talked to there looked at the specs for that stud and said that the "pitch diameter" is the dimension I should be measuring, which I don't quite understand. He suggested using a tap to clean up the threads, which also didn't make sense to me since the internal threads are pretty much gone.
He is going to run it by engineering and get back to me.

The new studs are correctly marked. They have a "3", "7" and "12" stamped into the ends of the studs. So either it's a manufacturing error, or there's something I'm missing.
I'm baffled at this point.

I'm attaching 3 photos showing the 3 different stud sizes in my "non-digital" calipers. They all show a diameter of right about .3125 (5/16")
Attachments:

Please Log in to join the conversation.

More
4 months 3 weeks ago #3213 by STEVE ELLS
Replied by STEVE ELLS on topic Loose exhaust stud on O-320 E2D
Good idea.

Let me know how that works,

Steve

Please Log in to join the conversation.

  • TOM BRAEUNIG
  • TOM BRAEUNIG's Avatar Topic Author
  • Offline
  • Senior Boarder
  • Senior Boarder
More
4 months 3 weeks ago #3210 by TOM BRAEUNIG
Replied by TOM BRAEUNIG on topic Loose exhaust stud on O-320 E2D
Hi Steve,
I had my IA look at the plane yesterday, and he recommended using an oversize stud instead of the heli-coil.
I ordered 3 sizes of oversize studs from Airpower, they are .003,.007 and .012 oversize. Lycoming P/N's are 31C12P03,P07 & P12.
My IA said that there's no need to tap the hole; the new stud will self-tap.
I'll probably start with the .003" oversize and see if that works, then work my way up if I need to.

Please Log in to join the conversation.

More
5 months 1 day ago #3209 by STEVE ELLS
Replied by STEVE ELLS on topic Loose exhaust stud on O-320 E2D
Hi Tom;

Yes you can install a Heli coil without pulling the cylinder.

You will be drilling a larger hole, then cutting threads in the head with a special Heli Coil tap.
Since you're working on what is the bottom of the head the metal cut by the drill and tap will fall down, not anywhere near the cylinder opening.

However, in order to gain good straight on access to drill and tap the head you may have to remove the induction tube and maybe the primer line.

In my mind the key to this is to take the time to make sure you're square to the exhaust port when you drill and when you cut new threads with the tap. A half hour prep to get the access you need will pay off big time.

Exhaust studs are not usually locked in place. I recommend new nuts, studs, washers and lock washers.

Let me know how it goes.

Steve
The following user(s) said Thank You: TOM BRAEUNIG

Please Log in to join the conversation.

  • TOM BRAEUNIG
  • TOM BRAEUNIG's Avatar Topic Author
  • Offline
  • Senior Boarder
  • Senior Boarder
More
5 months 2 days ago #3208 by TOM BRAEUNIG
Loose exhaust stud on O-320 E2D was created by TOM BRAEUNIG
While I had my cowling off today for some other maintenance, I noticed that one of the exhaust nuts on #2 cylinder had backed off. When I tried to re-tighten it it wouldn't tighten up, and I was able to pull the stud out pretty easily.
The threads on the stud look a little worn, so I went ahead and ordered a couple of replacement studs (lYC P/N 31C-12). I will probably try threading the new stud in using some loctite, letting it sit overnight and then trying to install and tighten a new nut on it.

If that doesn't work. I'm thinking my next step will be to install a heli-coil.
It it possible to install a heli-coil without pulling the cylinder. (I'd really like to avoid doing that if possible.)

Attachments:

Please Log in to join the conversation.

Time to create page: 0.264 seconds