Exhaust manifold studs on 911 engines can be a real PITA.
They commonly fail when exhausts are removed and the work involved in replacing broken studs can be costly and irritating.
What do we do when we have gone to all this trouble ?
We normally fit another 50p standard stud which may as well be made of green cheese.
Standard 911 Studs are made from a Grade 4 material which has a very poor shear strength.
The standard barrel nut corrodes to the stud quite quickly and can cause problems if exhausts have to be removed even after relatively short periods time.
The current trend is also to replace the barrel nut with a cheap and nasty Self-Locking nut with a flash of copper.
These nuts are slightly more corrosion resistant but only marginally and not much use.
Add to that the prevailing torque feature and the risk of another failure increases.
A correctly tightened nut shouldn't need this feature and I just don't think they are a good idea.
We have made a batch of Grade 5 Titanium studs and some matching nuts.
These have about the same strength as a Grade 12.9 Cap Screw and they will be difficult to break.
They have a 'dog point' on one end so they can be gently tightened into the head and then held in place with Loctite 266 which is a High Temperature thread locker.(this will be supplied with stud kits)
The opposite end of the stud is prepared with a 4mm AF socket head to allow tightening.
The threadlocker will also electrically insulate the threads and prevent bi-metallic corrosion.
We have also made Grade 5 Titanium Flange nuts with a reduced AF sixe that will pass though the heat exchanger.
We have also found a Thin Wall Socket that also passes through the heat exchangers to allow these nuts to be correctly tightened.
By using a suitable Ceramic Anti-Seize ( manufactured by Molyslip and also supplied) we believe that we can eliminate any further broken studs.
Titanium is extremely corrosion resistant and is used in marine environments so it should be good even on salty winter roads.
We are just organising exhaust manifold gaskets as currently only 42mm diameter parts seem to be available other than from Porsche.
