Rusted Nuts on Exhaust Manifold Studs

[mendez]

Hi,

I'm new to the forum. I'm trying to remove my exhaust manifold and the nuts on the studs are very rusted. While trying to remove them the actual stud became loose. Is it ok to remove the old stud? Any recommendations on replacement studs?

It's my first time doing this. My car is a 1977 911s

Thanks for the help!

[safe]

Accept your good fortune that the studs didn't break! Doesn't matter if the nut or stud that comes out.

[john walker's workshop]

Heat the nuts red hot and you won't break studs. Use the search box for tons of info.

[LukasM]

Follow John's advice, and don't force it if they are really not moving, better to do a few cycles of hot and cold, ideally with some penetrating fluid in between. Drilling out broken studs with the engine in the car is definitely not fun, even with the useful Stomski jig. If you really mess it up you get to remove the engine and the heads, and then you are in for a lot of work "while you are in there"...

Any studs that came out - count yourself lucky and replace them, ideally with titanium studs that won't ever corrode, or at least some freshly plated steel studs.

Then remount them with new copper nuts, that also won't seize.

[mendez]

Thanks a lot everyone. I dropped the engine to restore as much as I can. Should I apply anti seize to the new titanium treads? I guess I plan to replace the manifold, heat exchanger and exhaust at a later time and I want to make sure they can be removed if needed.

[PeteKz]

No, don't apply antisieze to the studs in the head. Yes, apply antisieze where the nuts thread onto the studs. If you don't have a torch, and you can get an access to the stuck nuts, cut a slot through one side of the nut with a Dremel tool. It's a PITA either way.

Re titanium studs: I know titanium is trick and cool and all that (and expensive), but I think the OE steel studs work very well at a fraction of the price. Just put antisieze on the outer threads before you put the nuts on.

[porschedude996]

a Pull studs and replace them with inconel studs. That’s what Porsche should have used.

[JoeMag]

If using copper nuts, is the torque spec still ~17 ft-lbs?

[porschedude996]

If you’re thinking of “running torque” on the locking nut, it isn’t that much added torque required to spin the nut on. I assume you are talking about copper plated locking steel nuts, yes?

[porschedude996]

I ran the numbers comparing stock OEM plain steel studs, nuts, washers to Inconel studs, washers, and nuts. All inconel.

Studs - 999 062 237 02 ($5.50 x 12) ($66.00) You could save some on non-porsche parts, $3.50 each x 12.

Nuts, Barrel, kit - 999 085 001 02 ($17.70)

Washer - 900 076 025 02 ($0.07) ($0.84)

Nut, Hex, Copper plated, locking ($1.47 x 12) ($17.64)

Plain Steel Exhaust Studs
$66
$18
$1
$18
$103 plus shipping

Inconel - ebay - $120 FREE SHIPPING

Search “Inconel Grade 10.9 Turbo Turbine Housing Exhaust Manifold Stud 45mm M8x1.25 (6P)”

Not too far off. The nuts have a reduced 12 point drive and a 3/8” deep craftsman socket slips through the holes in the manifold, which requires the “barrel” nuts.

[mendez]

Originally Posted by porschedude996

I ran the numbers comparing stock OEM plain steel studs, nuts, washers to Inconel studs, washers, and nuts. All inconel.

Studs - 999 062 237 02 ($5.50 x 12) ($66.00) You could save some on non-porsche parts, $3.50 each x 12.

Nuts, Barrel, kit - 999 085 001 02 ($17.70)

Washer - 900 076 025 02 ($0.07) ($0.84)

Nut, Hex, Copper plated, locking ($1.47 x 12) ($17.64)

Plain Steel Exhaust Studs
$66
$18
$1
$18
$103 plus shipping

Inconel - ebay - $120 FREE SHIPPING

Search “Inconel Grade 10.9 Turbo Turbine Housing Exhaust Manifold Stud 45mm M8x1.25 (6P)”

Not too far off. The nuts have a reduced 12 point drive and a 3/8” deep craftsman socket slips through the holes in the manifold, which requires the “barrel” nuts.

Thanks for everyone's reply!

I tried to look for the Inconel on eBay and is not showing up. See image below.
I though using Titanium was a better option than steel; why Inconel is better?

Thanks!

[Gonbad]

Inconel has even better heat resistance properties than Ti.

Most on here use the Inconel for the exhaust and Ti for the intake. I doubt in the grand scheme of things it makes a s**t bit of difference.

The steel studs are fine. I recommend the copper nuts. Ti and Inconel are for high temp race or aerospace applications. It has a cool factor and if you sleep better at night knowing that they are there then by all means spend the money.

[porschedude996]

I believe thet inconel has a higher service rating and the tensile strength is higher also. Inconel is 180ksi, like a grade 8 bolt.. Ti=130ksi, like a standard grade 5 bolt.

https://industrialmetalservice.com/resources/inconel-vs-titanium-understanding-the-use-cases-of-high-spec-metals/

Here is the link to the studs I bought.

[mendez]

Originally Posted by porschedude996

I believe thet inconel has a higher service rating and the tensile strength is higher also. Inconel is 180ksi, like a grade 8 bolt.. Ti=130ksi, like a standard grade 5 bolt.

https://industrialmetalservice.com/resources/inconel-vs-titanium-understanding-the-use-cases-of-high-spec-metals/

Here is the link to the studs I bought.

Thanks for the clarification! You forgot to past the link ; thanks again!