Exhaust Port Studs

[banquo]

Another easy one!
I've been reading threads (no pun intended) on sheared exhaust port studs, and am thinking about prevention rather than cure.
Idea is to remove the original studs now, and either:
1. Re-install, using copper grease or other anti-seize compound, or
2. Replace (as was suggested to me last night) with high temsile allen screws.

Anyone got experience of doing either of the above?
Are the stock studs loctited in, or just screwed into the head?
If using Allen bolts, I guess the length will be crucial: too long, and they will bottom out before tightening; too short and they might strip the threads in the head .
Would stainless be better than high tensile? I have expereince of stainless binding to stainless at high temperatures, but does it bind to alloy?

Every so often, it's good to have a simple mechanical question, that doesn't involve sparks, power commanders, torque cones and other things I don't understand..

[S.T.Chapman]

in the other thread you refer to it was clearly stated prevention was better than cure.
brush off any remaining rust and coat with copper slip prior to reassembley.
removal can be aided by allowing penetrating oil to soak in rather than try to disassemble dry.

if you want to be clever fit copper nuts if you can find them.
the studs gennerally were considered harden when new but the constant heating and cooling tends to aneal them to a softer state hence they snap.

[kiwidave]

I would be very cautious about swapping out studs Jake

I rather suspect there is a very good reason - metallurgy, heat, load bearing, soft alloy head, etc.... - why the factory installs and *EVERYONE* uses studs there and not screws/bolts.

Also...if yours are tight, why mess with 'em?

There is precious little room there to pull them. They usually only come out when not required to, as happened to me last month!

As Phild told me when I asked, there's no call for loctite because the heat melts it. Copper grease for me.

[banquo]

Dave - Idea of removing them was that they probably were not factory installed with anti-seize grease (judging by the rear axle for example...), and at some indeterminate point in the future, one or more is gonna have to come out, but will be seized solid. I thought, if they were EASY to get out now, they could be greased and re-installed. Maybe not...
I've got this prevention is better than cure philosophy...
I wasn't sure about the idea of replacing them, and tend to think like you, that everything I've seen has studs rather than bolts, so there should be a reason for it...

[S.T.Chapman]

Jake they should'nt come out but they do
reason being is that due to the different co-efficient of expansion of the two dissimilar metals.
which due to heating and cooling and and courtessy of the thread helix causes the stud to loosen.
well thats how I remember it from college
a long time ago now.

[Mr Fixit]

Collecting my first Harley on Saturday, copper grease on the exaust nuts sounds the best way to go.
Would nuts made from Phosphor Bronze work ok if so what size hex and thread are they as I could make some.
Also are there any other problem areas that require the copper grease treatment.

Mr Fixit

[kiwidave]

copper grease is very good on spark plug threads....you don't want any stripped threads there

[banquo]

Originally Posted by Mr Fixit

Collecting my first Harley on Saturday, copper grease on the exaust nuts sounds the best way to go.
Would nuts made from Phosphor Bronze work ok if so what size hex and thread are they as I could make some.
Also are there any other problem areas that require the copper grease treatment.

Mr Fixit

My list so far:
Back axle, back of brake pads, pad fixing pins, between muffler and header pipe, head steady bolts to cylinder head, and of course exhaust header studs...

[banquo]

Originally Posted by S.T.Chapman

Jake they should'nt come out but they do
reason being is that due to the different co-efficient of expansion of the two dissimilar metals.
which due to heating and cooling and and courtessy of the thread helix causes the stud to loosen.
well thats how I remember it from college
a long time ago now.

Yes, I think that's right Simon, but my alternative experience with steel studs in aluminium, with the heat of an exhaust and the spray of water and salt isthat they get seized solid, which is fine, if you never want to get them out. But, at some point in the future, that same heat and corrosion will cause one of them to break, and then that seizure would become a pretty big problem. Hence the idea of taking them out now (which I think I'll abandon until another day...).

[Mr Fixit]

Thanks for the info, guess I'll have to get a bike lift to do the rear axle.