Exhaust Manifold Nuts

[Cardiff Kook]

The old
STD-1410 Exhaust nut
MS35333-41 lock washer
AN960-516 flat washer
The Lycoming nuts are stainless steel and don't rust like the aftermarket nuts.
https://www.aircraftspruce.com/catalog/eppages/lycomingstuds_08-13229.php

I see this is manual. Are the parts Steve listed interchangeable with these?

Should i replace all the nuts/washers or just the two that pulled out!

Should i replace all the gaskets too!

Wouldnt mind trying out these nor washers either…

 

[Superbill]

I've got the same engine and have the same problem. I now check studs before flight. They haven't loosened in the last 25 hrs or so, but one in particular was getting loose regularly. I replaced it with one I found in my toolbox. It has a serrated flange. Not proper, but it seems to be working! The star washers would just break for some reason.

 

[Steve Pierce]

There are oversized studs as well.

 

[stewartb]

Oversizes come in -03, -07, and -12. The exposed end of the stud is stamped with the oversize value. McFarlane has them in their catalog. The pic shows how to identify them. I don’t have any -12s.

Studs aren’t supposed to easily twist in. It needs to be done with a torque wrench. If one goes in too easily? Go up a size.

 

[AkPA/18]

Confession time.
I have been using standard hardware store stainless nuts since the late 80s with great results. Not going to change but is that a bad thing?
Thanks
Mark

 

[skywagon8a]

Not to confuse, I've been using long brass nuts with success. They eliminate the heat generated rust on the studs by completely covering the otherwise exposed threads. They come with a fine thread for Continentals which I rethread for the Lycoming.
https://www.aircraftspruce.com/catalog/hapages/manifoldnuts.php?clickkey=3013405

 

[Steve Pierce]

Confession time.
I have been using standard hardware store stainless nuts since the late 80s with great results. Not going to change but is that a bad thing?
Thanks
Mark

Only if something happens, the Feds figure it out and they try and twist it into the cause. They tried that with the snap vents in the boot cowl of my Clipper. Went as far as to have an expert witness make a drawing of exhaust gasses coming out of the exhaust pipe and up into the snap vent. They weren't real happy when I laughed at them. They asked me why I was laughing so I told them the toxicology report didn't show any carbon monoxide in my system. "What tox screen?" "The one they took when they admitted me to the hospital." "Do you have a copy of that?" "No, sent it to the NTSB along with those logbooks that you have there." 8 hours of that ****, I cover my ass.

 

[cubdriver2]

Not to confuse, I've been using long brass nuts with success. They eliminate the heat generated rust on the studs by completely covering the otherwise exposed threads. They come with a fine thread for Continentals which I rethread for the Lycoming.
https://www.aircraftspruce.com/catalog/hapages/manifoldnuts.php?clickkey=3013405

My buddy buys brass hex rod and makes his own

Glenn

 

[BC12D-4-85]

https://www.mcmaster.com/products/brass-nuts/

Several designs of 5/16x ** brass nuts. The serrated flange ones look interesting.

Gary

 

[cubflier]

Years ago I had some issues with rust on my exhaust nuts. I was told I was using the wrong nuts. So I went to the local aircraft parts store and asked if they had the correct Lycoming exhaust nuts. They said yes and asked how many? I replied I'll take a whole box. They asked are you sure. I said yes. Then the bill came in. I paid the stupid tax on that move. Still have most of that box left.

Jerry

 

[stewartb]

I'm pretty sure the nuts on my factory Lycoming are SS. When I pulled the temporary caps off and installed the exhaust I used Nordlocks. There isn't enough stud sticking through the nuts to worry about threads getting fouled but I think the studs are stainless as well.

 

[cubflier]

The Lycoming nuts are ss as far as I can tell. They are also an actual Lycoming part from what I was told when I inquired about the full box that I purchased, hence the price. That may have something to do with the legal requirement that Steve was alluding to.

Jerry

 

[Cardiff Kook]

So- is it not legal to use anything but what is in the manual?

Should i go ahead and replace all the gaskets while i am at it?

 

[stewartb]

Replace gaskets on cylinders that you unbolt the exhaust from. Otherwise, if they ain’t broke, don’t fix ‘em. If you’re wanting to R&R all four? Ask your mechanic for guidance.

To your question about nuts, if you have to ask? The safe decision is to use authentic airplane parts.

 

[BC12D-4-85]

Older A&P's would lay a straight edge (screwdriver, socket extension, whatever) across the exhaust header flanges to look for warpage (owner sees). They can get overtightened and that bends the ears some, especially with the newer thicker exhaust gaskets now available. They would then do whatever it took to make them flat again. Also they looked at the cylinder's exhaust port mating surface for erosion caused by exhaust leakage. There's a special facing tool that can fix that to a wear point.

Gary

 

[Steve Pierce]

I wouldn't replace the gaskets unless they are leaking. The hardware I listed is what is called out by Piper and Lycoming. Been using it for years and years without issue. If it didn't work there was something else going on.

 

[dirthog4]

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

 

[skywagon8a]

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

The small ones have the crimp. The larger ones do not.

 

[hotrod180]

So- is it not legal to use anything but what is in the manual? ....

Just put any old thing on there.

 

[Cardiff Kook]

This one isnt even missing a nut.

I take it thar is blow by?

Note the hardware on that one has a thicker washer than others AND not star washer

 

[Steve Pierce]

Looks.good to me. If you had a leak it would show on the spark plugs etc

 

[Cardiff Kook]

Different studs?

These exhaust studs are not the same. First picture is what i think is factory/correct- it has a rounded edge and looks similar to the others.

2nd one was put in by mechanic w helicoil a year ago.
Threads look finer to me and no rounded end.

Am i seeing that correct?

 

[Steve Pierce]

When I said it looks fine to me I meant that it didn't look like it was leaking.

 

[skywagon8a]

See that jagged line on the exhaust stack which starts near where the fin is broken then proceeds up towards the welded flange? Check that to see if a crack is forming. It may not be cracked yet. That is what it looks like when it is thinking of cracking.

This spark plug is covered with a light brown soot. That is an indication of an exhaust leak. Check the exhaust gasket on that cylinder. The exhaust nut is missing.

 

[Cardiff Kook]

Should I use a high temp threadlocker on these nuts?

 

[Gordon Misch]

Cardiff - your questions are legit, and good on you for not just guessing at the answers.

But I'm gonna be "that guy" to say the following: Many of the answers are to be found in the Lycoming overhaul and parts manuals. And more importantly, your mech / IA should be very much involved with deciding on remedies when these issues come to light. Maybe he/she already is, but it's not clear from the posts.

 

[BC12D-4-85]

https://media.mcfarlaneaviation.com/documents/exhaust-nuts-and-studs.pdf

https://www.mcfarlaneaviation.com/products/category/exhaust-system/?page=4&make=Lycoming&series=320&model=O-320-A2B

McFarlane has some FAA/PMA options for nuts and studs. Any experience with them?

Gary

 

[Cardiff Kook]

Cardiff - your questions are legit, and good on you for not just guessing at the answers.

But I'm gonna be "that guy" to say the following: Many of the answers are to be found in the Lycoming overhaul and parts manuals. And more importantly, your mech / IA should be very much involved with deciding on remedies when these issues come to light. Maybe he/she already is, but it's not clear from the posts.

Thanks.

I consulted 3 local a&p/IA over the phone about it as well.

Two big problems:

1. I dont have a mechanic on my field. Tiny field.

2. They want me to “fly it to them” to take a look.

I dont do anywork on the planes without signoff. Just figuring out what needs to be done and get the parts. This issue has already been addressed twice by a mechanic.

I certainly wish I could just hand my credit card to someone at times- thats for sure. I am sourcing stuff out of necessity not to save $.

These guys are so busy that getting them to drive an hour round trip to look at a missing nut is a hard sell. It ends up being a 1/2 or more out of there shop just to look at the plane- and they are all swamped.

Good news is we are supposedly getting a shop a few days a week come September, I mean October. November. They say they are shooting for December 1…

I am logging time towards an a&p myself- doubt I wil get their but at this rate who knows.

 

[Cardiff Kook]

I saw from another thread the torque for the exhaust nuts is 160-180 in lbs. Sound right?

Mechanic who put in last stud w helicoil put the stud pretty high up in the cylinder. He said he did that as previous one had pulled out. Doesn't leave much bite at end for nut- should should that be backed out or just left as is?

 

[Gordon Misch]

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
.