Exhaust Stud Replacement

[hamer]

I'm going to be changing my exhaust gaskets to the no-blo type. Upon inspection it appears that the exhaust studs are due for replacement (rusted pretty badly). My plan was to chase out the threads with a tap as they seem pretty stiff. Besides that I plan to install the new ones with a little bit of anti-seize.

I found torque specs for the stud and nut in the lycoming manual. Is there a recommended method for installing the stud? I know the "double-nut" method is common for installing studs, however I wasn't sure if there was a more precise/preferred method or maybe an installation tool?

I plan to do this under the supervision of my A&P, however as always I like to be up to speed and educated before I jump into something, supervision or not.

Thanks,

 

[Tom-D]

There is a stud removal tool.
The best way I know of for getting them out is to heat the cylinder head around the stud, freeze the stud removal tool, clamp it on the stud and try to turn it out.

the tool
https://www.ebay.com/i/173735261461?chn=ps

 

[Checkout_my_Six]

I have the 1/4” snap on stud tool if you’d like to buy it. ($65) they are more new. Make sure you don’t have the locking kind (Rosan). If so there is an exspensive lock removing tool required.

 

[Stewartb]

Changing exhaust studs because they have some rust on them is creating work. As long as the nuts accept the required torque I wouldn't change them. The new ones will get rusty, too.

 

[Let'sgoflying!]

yes, if you start messing with those, be prepared that it ‘might not work out’ & a send-off to a cylinder shop could become necessary.

 

[Tom-D]

yes, if you start messing with those, be prepared that it ‘might not work out’ & a send-off to a cylinder shop could become necessary.

there are tools to drill the old stud out with cylinder installed. they ain't cheap,

 

[hamer]

There is a stud removal tool.
The best way I know of for getting them out is to heat the cylinder head around the stud, freeze the stud removal tool, clamp it on the stud and try to turn it out.

the tool
https://www.ebay.com/i/173735261461?chn=ps

Thanks Tom

I have the 1/4” snap on stud tool if you’d like to buy it. ($100) they are more new. Make sure you don’t have the locking kind (Rosan). If so there is an exspensive lock removing tool required.View attachment 70921

View attachment 70919

Unfortunately I need the 5/16-18

Changing exhaust studs because they have some rust on them is creating work. As long as the nuts accept the required torque I wouldn't change them. The new ones will get rusty, too.

Well it's not only because they are rusty. In trying to remove the nuts they seized and ended up pulling the stud out with them. Since they are out I feel like I should replace them. I don't see the point in reinstalling rusty studs/nuts.

My question was more geared at how to reinstall them properly.

 

[Tom-D]

Well it's not only because they are rusty. In trying to remove the nuts they seized and ended up pulling the stud out with them. Since they are out I feel like I should replace them.

Yes replace them with an oversize step shoulder stud grade 8 from NAPA.

I never said that

 

[Checkout_my_Six]

Oh no.... now we’re all gonna die... just not today.

 

[flyingbrit]

Yes replace them with an oversize step shoulder stud grade 8 from NAPA.

I never said that

If the studs are stiff in the head as OP says, why would you want an oversize?

 

[Tom-D]

If the studs are stiff in the head as OP says, why would you want an oversize?

he also said some pulled out, It's best to thread the hole to oversize and put a clean stud in place

also read the post I was replying to

 

[hamer]

Only had to replace 2, the rest were serviceable.

 

[Dan Thomas]

The Lycoming stud is already slightly oversize on the head end. They want that thing in there tight. Anti-seize could let it vibrate out.

Section V of the 60297 Lycoming Direct Drive overhaul manual calls for those studs to need a minimum of 40 inch-pounds of torque going into the head. With the wrong (cheap) tap you could remove enough metal so that they're loose.

 

[Dan Thomas]

If the studs are stiff in the head as OP says, why would you want an oversize?

Corrosion between the steel stud and aluminum head can make it very hard to remove.

 

[hamer]

The Lycoming stud is already slightly oversize on the head end. They want that thing in there tight. Anti-seize could let it vibrate out.

Section V of the 60297 Lycoming Direct Drive overhaul manual calls for those studs to need a minimum of 40 inch-pounds of torque going into the head. With the wrong (cheap) tap you could remove enough metal so that they're loose.

You are correct. I realized this when I got the new studs and the nut would only bolt to one side of it. Thankfully crisis averted. Thanks for posting, I should have mentioned that for future thread readers.

 

[Tom-D]

That interference fit is why you heat the head prior to removing the stud. those studs come in .002/4/6 over, each has its own tap size. each size has three taps, a taper.plug and bottoming to get threads to the bottom of the hole.