Exhaust header torqued down but two threads are not showing

[fixnflyguy]

The "thread rule" is a much understood bit of hogwash. There are many factors that can, but typically don't apply. I wont go into all the details, but thread protrusion is a mix of bolt/nut type, and shear/tension application. At the end of the day, anything protruding from the end of the nut has nothing to do with retention or safety. As a general rule, it validates if the bolt is long enough, or too long..a much more important factor in stressed applications. With a stud, the threads are infinite, and anything flush or better is 100% of need.

[rv7charlie]

Maybe an engineer should jump in here; not all studs have 'infinite' threads. It might not be a factor on an exhaust system, but my understanding is that studs loaded in shear have an unthreaded portion that actually extends into the parent material so that the shear load is on the unthreaded portion of the stud.

I ran into this while designing a motor mount for my alternative engine. My engineer buddy kept working me over if it looked like I was going to violate that rule. If I understood my engineer friend correctly, that's the reason studs are used instead of bolts in highly shear-loaded applications.

I hope this isn't nitpicking...

Charlie

[lndwarrior]

Originally Posted by JonJay

I assumed you torqued the stud to the correct range? What's wrong with going with the next size stud?

Yes, they are properly torqued.

Didn't know that changing out the stud was an option. How hard is this to do and how do you do it?
Thx
Gary

[rvbuilder2002]

Originally Posted by lndwarrior

Yes, they are properly torqued.

Didn't know that changing out the stud was an option. How hard is this to do and how do you do it?
Thx
Gary

Excuse me for sounding a bit snarky, but this is the point in the story (and it repeats it self over over over here and on other internet forums) where the poor builder has to choose from all of the well intended advice in an on line forum.
He does choose, and attempts to do some work he knows nothing about (and was totally un-needed). He then ends up spending a bunch of money having someone who does know what they are doing, repair the threads in their cyl head that are now damaged.

[lr172]

Originally Posted by rvbuilder2002

Excuse me for sounding a bit snarky, but this is the point in the story (and it repeats it self over over over here and on other internet forums) where the poor builder has to choose from all of the well intended advice in an on line forum.
He does choose, and attempts to do some work he knows nothing about (and was totally un-needed). He then ends up spending a bunch of money having someone who does know what they are doing, repair the threads in their cyl head that are now damaged.

+1 here. This is a 5/16" nut holding a 3 pound exhaust pipe. I don't see how one could recommend removing and replacing an exhaust stud because one or two threads are not exposed. That is a potential costly mistake waiting to happen for the inexperienced. As mentioned previously, there is no locknut and therefore no need for solid thread engagement in the locking mechanism.

To the OP and others, this is great forum with a HUGE wealth of information. I can't even count the invaluable guidance and tips that I have received. However, just like any other public forum, not all of it is accurate or appropriately applied. Take in the wealth of information, but don't ever stop using your judgement and common sense. Also, there is a much larger source of information out there to help you make good judgement calls if your experience is limited. "trust but verify" is one of my favorite sayings.

Larry

[bret]

I did not like the condition of my studs so I changed them out, do not want a chance of a pipe coming loose and one of those fire breathing dragons loose inside the cowl, That would be a very bad day!

[lndwarrior]

Originally Posted by rvbuilder2002

Excuse me for sounding a bit snarky, but this is the point in the story (and it repeats it self over over over here and on other internet forums) where the poor builder has to choose from all of the well intended advice in an on line forum.
He does choose, and attempts to do some work he knows nothing about (and was totally un-needed). He then ends up spending a bunch of money having someone who does know what they are doing, repair the threads in their cyl head that are now damaged.

That's funny - and probably all too true! Definitely not looking to get in over my head.

[Walt]

Remove the thick flat washer leaving nut/lock washer only, if you have one thread thru the nut you are good to go. End of story.

[BillL]

So let's score this.

The pros (Walt, rvbuilder2002, aerhed ++) say leave it, it is fine.


The risk of leaving it is - possible argument with the inspector? Most guys leave the engine alone. There are even a bunch of nylocks there and even the most picky pass them.

Or remove the studs - the risk is a broken stud, or pulling some threads out with it. A dark possible path of things can happen here. Is an exhaust stud, not a "cold one" that has fewer risks.

Hmmmmm.

[A2Jake]

1st, Need a better picture, at a lower angle.

Most likley, remove the flat washer, install brass nuts, DONE !

From the picture, my attention would be more focused on, if that is a spark plug lead routed thru and touching the exhaust pipe

If the engine has much time, inexperienced persons removing those studs will most likely result in??

Enjoy