Exhaust Manifold Nuts

[TomT]

There is a specified torque for the stud into the helicoil, and a specified minimum length for the stud reveal. I think if those both cannot be met you must go to an oversize. Sorry, I don't have those specs.

Tom

 

[Cardiff Kook]

Please - Look in the overhaul manual and 43.13 for torque specs and nut engagement requirements, rather than an internet forum - even including this one
.

Understand and appreciate the sentiment but Steve Pierce said he couldn’t find any values. There is a whole thread in here of people trying to track down values.

https://www.supercub.org/forum/showthread.php?56902-Exhaust-Nut-Torque

I figure if the experts cant find it then it would be a fools errand for me to try to track them down.

Will try to locate that overhaul manual but if Steve and the other supercub whiz kids on here couldnt find it I doubt a rookie like me will have any luck. Also- i have an o-290d2 for what its worth.

 

[stewartb]

Read posts 11-15. The answer is right there.

 

[Mauleguy]

I have always just used stainless steel nuts and stainless steel split washers with Permatex anti seize lubricant applied to threads and never had an issue. Maybe just lucky but it works for me. I have never torque them to any particular torque either, just what feels good. Never had an exhaust leak with new gaskets.

 

[Cardiff Kook]

Read posts 11-15. The answer is right there.

Now I am confused.

I think I have all the answers. I ordered the hardware I need (stainless lycoming nuts.). Have the torque values. I am good.

I was just pointing out to Gordon that as far as I can tell the torque values arent apparently in the overhaul manual. Thats all.

 

[skywagon8a]

Page 190 has the standard table of torque limits. https://www.lycoming.com/special-service-publication-no-1776-5

 

[Gordon Misch]

I have that 1973 overhaul manual, with the spec Steve mentioned. I wasn't aware of its being superseded. That manual also gives generalized specs for a variety of thread sizes on pg 52. Gives 110 - 150 in-lb for lubricated 5/16-18 threads. As a practical matter, I like Maulguy's TLAR spec.8)

Edit:
Pg 1-41 in the pub Skywagon linked, gives 204 - 228 in lb for all 5/16 nuts. I think that would "feel" better to me.

 

[Spornrad]

Have some original small continental brass nuts and there crimped slightly.

I also have the original small continental brass nuts and they are crimped slightly. Never had problems with them and they are easy to remove. No rust!

 

[Cardiff Kook]

I had a mechanic out to look at this yesterday.

I previously ordered all factory parts.

On the Lycoming stud i ordered each side of the stud appears to have a slight variation in threading. The 1410 nut goes on one side and not the other. Is that normal or do I have a bad part?

 

[hotrod180]

....On the Lycoming stud i ordered each side of the stud appears to have a slight variation in threading. The 1410 nut goes on one side and not the other. Is that normal or do I have a bad part?

Do you have a thread gauge?
As I recall, the exhaust studs on my old Cont O-300 were coarse thread (5/16-18) on one end,
and fine thread (5/16-24) on the other.

 

[cubdrvr]

Page 190 has the standard table of torque limits. https://www.lycoming.com/special-service-publication-no-1776-5

......or use my Grandpa Johnnie's farm torque ............tight plus 2 turns.

 

[aktango58]

Interesting thread, but if I may make a side trip out of curiosity...

There is discussion of "oversized studs". Do these use the same hole and threads, or is this something that one runs a tap up to clean/recut existing threads to something larger?

I deal with some stud issues on other machines and had never thought about having a slightly oversized stud to install if threads got 'stretched' a hair. I always found a bit of extra permatex or loctite solved a myriad of mechanic ignorances

I have had so many things vibrate apart on gravel roads, heavy equipment and such I seem to always put loctite on nuts and bolts when going together. The gel tube with a twist end has become my favorite tool.

 

[skywagon8a]

Interesting thread, but if I may make a side trip out of curiosity...

There is discussion of "oversized studs". Do these use the same hole and threads, or is this something that one runs a tap up to clean/recut existing threads to something larger?

Lycoming supplies studs which have oversized diameters for the portion which screws into the cylinder head. Same thread pitch just a larger diameter. Over time sometimes the studs work loose and will not stay in the cyl head. The larger diameter fixes it unless the threads have been botched up. Then it is time to install a helicoil which is a set of steel threads which are screwed into a new set of threads tapped into the cyl head.

 

[aktango58]

Lycoming supplies studs which have oversized diameters for the portion which screws into the cylinder head. Same thread pitch just a larger diameter. Over time sometimes the studs work loose and will not stay in the cyl head. The larger diameter fixes it unless the threads have been botched up. Then it is time to install a helicoil which is a set of steel threads which are screwed into a new set of threads tapped into the cyl head.

Thank you!

 

[Steve Pierce]

You need a mechanic that knows what they are doing and can explain things to you. If the nut doesn't fit it is because it is a tighter thread for the cylinder head. Look at the two ends of the stud, then look at the factory studs sticking out of the head and your question will be answered.

 

[Cardiff Kook]

You need a mechanic that knows what they are doing and can explain things to you. If the nut doesn't fit it is because it is a tighter thread for the cylinder head. Look at the two ends of the stud, then look at the factory studs sticking out of the head and your question will be answered.

My mechanic didnt know that about the stud[emoji853]I think most of his work is on continentals.

My guess is next comment is “find a new mechanic”

 

[Steve Pierce]

My mechanic didnt know that about the stud[emoji853]I think most of his work is on continentals.

My guess is next comment is “find a new mechanic”

Yea, I didn't either and the first time I went to install one I noticed the ends were different and had to figure out which one went in the head, between the exhaust nut only going on one end easily and seeing that end matched what I was seeing on the other studs I used deductive reasoning. Same with witness marks when trying to determine orientation of a part someone else removed. Lots of little things. The more you do the more you figure out and you really figure stuff out when you screw it up. One that comes to mind is the crank sensor on a Light Speed ignition on a Carbon Cub. That cost me a couple of trips to a neighboring airport and the cost of a chewed up sensor. We are all gonna be real smart when we are 6 feet under.

 

[Troy Hamon]

Lycoming supplies studs which have oversized diameters for the portion which screws into the cylinder head. Same thread pitch just a larger diameter. Over time sometimes the studs work loose and will not stay in the cyl head. The larger diameter fixes it unless the threads have been botched up. Then it is time to install a helicoil which is a set of steel threads which are screwed into a new set of threads tapped into the cyl head.

I haven't measured, so perhaps they are greater diameter as you state. But they appear to be the same diameter but with thicker threads on the portion that is installed into the cylinder. But I was never clear if the oversize was technically measured as thread thickness, which is visually apparent, or thread diameter, which is not.

 

[skywagon8a]

I haven't measured, so perhaps they are greater diameter as you state. But they appear to be the same diameter but with thicker threads on the portion that is installed into the cylinder. But I was never clear if the oversize was technically measured as thread thickness, which is visually apparent, or thread diameter, which is not.

It's been a long time since I handled one of these. Perhaps it is just a fatter thread? I seem to remember it being given a + size. Just what the + is, I can't be certain at this point in time. I thought it was given in so many thousands oversize. I took that to mean diameter. It could be a little of both.

 

[Steve Pierce]

This shows which end the nut goes on.


Here is a standard stud.


And a P03.

 

[hotrod180]

I'm assuming these are Lycoming studs.
As I recall, the exhaust studs for small continental are coarse thread on one end (cylinder), and fine thread on the other (nut)?

 

[Cardiff Kook]

OP- After many many hours I think I found root of this being a recurring issue.

The weld on one of the exhaust manifold prevents nearly any socket from getting a proper grip on the rear nut on cylinder 2. You can tighten it- but not to proper torque.

Ground socket sidewall needs to be too thin to hold. Will crack.

I think that weld needs ground down.

All other cylinders standard swivel socket works fine.

 

[BC12D-4-85]

Last Century minus 20 years I saw a similar ground socket in A&P's box. When asked he replied it was for just that application. And it had a crack. He'd TIG weld it until it repeated cracking. Nothing else worked like that old tool....almost paper thin. Maybe a crows foot socket would work if ground a bit and offset just right?

Gary

 

[Gordon Misch]

Carve away a segment of the socket without thinning it? With a 12-point socket it probably wouldn't take a huge amount?

 

[skywagon8a]

You can tighten it- but not to proper torque.

Sometimes you just have to use your best judgement as to the correct torque....not difficult.