Stripped exhaust stud on 0-320

[gregewert]

What is the best way to deal with a stripped exhaust stud? As an old VW mechanic we had oversize studs - is that possible or do you have to use a helicoil?

[Steve Pierce]

I know Continental has oversized exhaust studs. I will check on Lycoming today. I have heli-coiled them in the past with no problem.

[Lownslow]

When you say "stripped", I am assuming you mean the threads of the exhaust stud and that you still have some stud material protruding. In most cases, the stud can be removed and a standard stud reinstalled. I will recommend that if you do not have the experience or "know-how" to complete thius task, it should be left to a reputable mechanic. It has been a few years since I have done this, but I have done several this way. The biggest challenges are working upside down and having "close-quarter" operating room where the exhaust port is located.

I have have been successfull in removing the stud by clamping a good set of vice grips in nearly new condition to the stud and see if the stud will turn. It is important that you utilize the vice grips to get as strong of a grip on the stud as possible. This should be done in a manner that it turns with minimal force and the pliers do not continue "stripping" the stud. If it does not turn, attempt the next step of heating the cylinder exhaust port around the stud with a torch, allowing the aluminum to expand that will help loosen the stud for turning. This step also depends on a very good grip on the stud. Again, using a torch to heat the aluminum must be done carefully with all hazards considered to be performed safely.

If the stud has broken off, it must be ground flat and then drilled to accomodate an "easy out " removal tool. Then carefully heated as described above and then some experienced manipulation of the tool to extract the remaining stud. Again, this must be done vey carefully to drill the center of the stud for the extracting tool so as not to damage the aluminum cylinder head material. If the aluminum is damaged, I suggest removal of the cylinder and the cylinder shopped to have the original threads drilled out and a helicoil installed. This can be done in the field, but can be extremely difficult to drill correctly without special aligning equipment. I would refer to the latest Lycoming rec on using LocTite on the new stud installation, which I don't have available.

Someone may have a new and improved method, but this is how I've done it. Hope this helps.

Lou S.

[Stephen]

Steve have you drilled out for helicoils with the cylinder on the plane? LNS has a point about the difficulty. With cowling, exhaust, intake, plugs and intake removed it is wide open, but upside down.

[Steve Pierce]

I have welded a nut to what is left of the stud and removed it that way. There are drilling fixtures available that allow you to drill the stud out. I have a drill stud which goes in the hole in the exhaust manifold and allows you to center drill the hole in the broken stud. Would be glad to send it your way if you can use it. I also have an exhaust flange resurfacing tool that works real nice for those eroded exhaust flanges. There is an attachment for drilling the studs for this tool. The guy that made them no is no longer manufacturing them but offered to loan me his to copy. I can get it and forward on if needed. I couldn't find anything on oversized Lycoming exhaust studs.
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[Lownslow]

Quite interesting and useful tools to have around there Steve. The alignment is crucial for all drilling required, especially the final drilling for the helicoil tap. That's why I suggest removal to shop if you don't have tools to ensure good alignment. I guess welding the nut to the stud has to be done very carefully too, grounding directly to the stud to prevent welding of things you don't want arced together, unless you gas weld. I've never tried that one. I think one key point is to try to maintain a portion of the stud that can be grasped by some sort of tool. As I have seen in nearly all cases the stud will turn out when the stud boss is heated with a torch and while gently applying pressure to turn it out. The 5/16 studs on the Lyc's are much better if caught early than the 1/4" on the Continentals. Those little dudes have aquired some unique names when I work on them.

Lou S.

[gregewert]

The stud came out - the threads in the aluminum block are gone - so I guess from everyone's comments that a helicoil is the way to go???

Greg

[Lownslow]

It is the best and cheapest way, imo.

Lou S.

[Steve Pierce]

I agree.

[tferraro]

For general information... Lyc exhaust studs do come in oversize - typically the oversize amount is stamped on the end of the stud. You can get them in .003 increments up to about .012 over. I've replaced many over the years without having to mess with helicoils.

[Stephen]

Are over-sized studs self tapping? Can't imagine how one could tap in .03" incremments.

I would assume that Lycoming sells these over size studs????

[Steve Pierce]

For general information... Lyc exhaust studs do come in oversize - typically the oversize amount is stamped on the end of the stud. You can get them in .003 increments up to about .012 over. I've replaced many over the years without having to mess with helicoils.

Where do you get them? I searched my Lycoming Parts Manual, Overhaul Manual and Service Bulletins, Instructions and Service Letters.Couldn't find anything. Found all the stuff for TCM and even have some of those but am lost on the Lycomings.

[tferraro]

Steve... I get mine usually from Tex Air parts here in Dallas.... I have also picked them up from Fletchair (the grumman guys). I think I saw them in the Sac Skyranch listing one time too... the part number is 31C-12 (Standard) followed by a P03 (.003 over) or P07 (.007 over). I 'm pretty sure our favorite engine or cylinder shops could supply them too. Most of the time a .003 oversize does the job nicely... rarely if it's really stripped out, the .007. I noticed in the aircraft spruce catalog they mentioned they had SS studs and in the copy said "oversized coming soon". Hope this helps.

[Troy Hamon]

We got some from Alaska Aircraft Engines at PAMR in Anchorage. Apparently they even make 12s, though the mechanic recommends helicoil back to standard rather than using those.

[Lownslow]

OK, help me out here. Do they sell an oversize tap with them to re-thread oversize? Or is it designed as "self=tapping"

[Steve Pierce]

tferraro, Thanks for the info, that is good to know.

[Steve Pierce]

Found them. 31C12, 31C12P3, 31C12P7 and 31C12P12. Those plus 31C12P12 are $16 opposed to $2.70 for the standard. Cheap if it saves pulling the cylinder.

[Stephen]

OK, help me out here. Do they sell an oversize tap with them to re-thread oversize? Or is it designed as "self=tapping"

Yes.....tell us!!!


Plus....can you accurately hand drill out for a helicoil, using the existing stud hole for alignment?

[Steve Pierce]

I am sure you can buy an oversize tap but I have installed them in Continentals judging how much oversize by how much driving torque it takes to install it. It has a taper at the end that makes it easy to start.

[Stephen]

Talking to my local engine shop they sell the oversized studs made by Superior. They said that in the field they can be installed by the old double nut trick, no tapping it out first, if the threads are completely gone they recommend helicoils.

[Steve Pierce]

I have a cool tool for installing them. It is nothing more than a long nut with a set screw inside it. You screw the stud in until it bottoms out on the set screw and then screw the stud in using the hew of the tool.

[Stephen]

Thanks Steve, I can imagine how to make one..easily.

Change in topic....Does anyone know when the 0320 C2B narrow deck engines were made?

[Steve Pierce]

Lycoming engines manufactured before 1964 (1971 for 540 series and 1975 for 720 series) were of narrow deck design. These engines used cylinder base hold down plates and internal-wrenching type cylinder base nuts. After these dates, Lycoming engines became "wide deck", Wide deck engines have regular hex type cylinder base nuts and a thicker cylinder base flange (approximately 3/8" thick). The thicker cylinder base flange makes the wide deck engines slightly wider than the narrow deck engine. The switch from narrow deck to wide deck did not change the model number of the engine even though cylinders and crankcases are not interchangeable. Another method you can use to distinguish narrow deck from wide deck is by the engine serial number. If the serial number ends with the letter "A" it is wide deck-; e.g. L-82374-27A.

This is from the "Sky Ranch Engineering Manual" by John Schwaner on the operation, failure and repair of piston aircraft engines. This is a very good book and is available at http://www.sacskyranch.com/ or in Trade-A-Plane.

The "C" designates that the engine was converted from a high compression "B" engine to a low compression "A" engine.

[Gilbert Pierce]

I don't believe Lycoming made a narrow deck C2B. The C2B is an B1A or B2B (160HP) engine converted from 160 hp to 150 hp by using the 150 HP lower compression pistons. This was done via Lycoming Service Letter L126A. You then stamped a C in place of the first B making it a C1A or C2B. This letter is obsolete but in 2000 could still be obtained from Lycoming. I did this to my O-320-B2B when we rebuilt it so I could burn auto fuel.

The Service Letter also says you can get a new name plate for $1.50. Not today-I got one in 2000 as mine was missing. $125.00 and letter from the FSDO telling Lycoming it was OK to issue a new name plate.

[Stephen]

Thanks Steve and Gilbert,

What I'm working on is what looks like was a "C"...then stamped over as a "B", converted to a 160 hp. It's a narrow deck. Oh course, no paper work...which I need to get sorted out.

I'd say that the past owners of this engine just could not make up their minds in what they wanted 160 - 150 - 160......

And it's all in a PA-20. Looks like it might have been done similar to Copper River STC.

[Hillbilly]

I have a cool tool for installing them. It is nothing more than a long nut with a set screw inside it. You screw the stud in until it bottoms out on the set screw and then screw the stud in using the hew of the tool.

You can buy "long nuts" off the shelf where they sell threaded rod, they use them for couplers.

Another good trick with a broken stud is take the Tig welder and stack beads on it until you have a 1/2" inch or so stack. the heat will usually free the stud and you just screw it out by the "handle" you made. ('course with vise grips)

[JoeB]

Another good trick with a broken stud is take the Tig welder and stack beads on it until you have a 1/2" inch or so stack. the heat will usually free the stud and you just screw it out by the "handle" you made. ('course with vise grips)

Come on Hillbilly, Even I use a point-n-shoot MIG when a weld a nut on a broken stud...TIG welder...what do you think we all are, rich???

[Hillbilly]

Another good trick with a broken stud is take the Tig welder and stack beads on it until you have a 1/2" inch or so stack. the heat will usually free the stud and you just screw it out by the "handle" you made. ('course with vise grips)

Come on Hillbilly, Even I use a point-n-shoot MIG when a weld a nut on a broken stud...TIG welder...what do you think we all are, rich???

Well, I dont mean welding a nut on it, cant do that if its below flush. But as far as Tig welders go Shucks, I'm a hillbilly I made mine out of Duct tape (of course) an old microwave, a high powered fence charger and some tractor parts...oh yeah and some bailing twine...the upside is I got the only welder on the block with a picture of an upside down burning cow on it....

(might bring a strong tolerance for electric shocks to this game...)

[gregewert]

Thanks to all who helped - looks lke I can use a self-tapping oversize stud and save some work.

Greg