I see many threads about this. What is the consensus on long term successful exhaust flange bolt replacement with studs.

I know auto parts stores have the bolt/stud size incorrectly listed for our H3’s. It is M8x1.25. Dorman has it incorrectly listed as M10, so the parts search is going to be off everywhere.

I bought a doorman M8x1.25x50.8 kit, steel zinc cromate coated https://www.dormanproducts.com/p-640-03422.aspx

Would stainless studs be better? Im not going to drop $300 on some of the extreme fancy hardware ive seen.

Wondering how the kit I got is going to react with the aluminum head and my stainless magnaflow that is going on. I am in the process of the swapping in a 2007 3.7l into my 2006 3.5l and plan on keeping the H3 indefinatly as i bought it new.

 

Stainless is brittle compared to carbon. High temp anti-seize should be used.

 

These are the parts that i've used when i fixed the broken exhaust manifold bolts. Also, i have to fix the old and rusted out driver side exhaust manifold heat shield 'cause i can't find or buy a new one.

 

Still No Leak 11yrs Later!🕺

Quote:
Originally Posted by hummerz
While under my rig I noticed 1 of the exhaust studs broken where the exhaust pipe bolts to the manifold. Knowing there is a problem with the oe manifold bolts to the head I decided to pull the exhaust manifold.

Original bolts to the head are class 9.8 rating, I'm upgrading to class 12.9 rating studs

First I ordered the parts (from ebay)

VICTOR REINZ Exhaust Manifold Gasket MS19755 $10.99
VICTOR REINZ Exhaust Ring Gasket Victor F32146 $9.45
DORMAN 03142 Exhaust Manifold Stud and Nut $6.00
9 M8 x 1.25mm High Tensile Alloy Steel Exhaust Manifold Stud Kit $20.00

$46.44 TOTAL COST

The Seller Accepted $20.00 Shipped, For The Stud & Nut Kit:

9 Piece M8 x 1 25mm High Tensile Alloy Steel Extended Exhaust Manifold Stud Kit | eBay







Designed for extreme and high temperature applications where failure is not an option!

Obsidian 9 Piece Kit Includes
• Nine Obsidian manifold studs (Class 12.9 alloy steel; M8 x 1.25mm x 45mm)
• Nine Obsidian nuts (Class 10.9 alloy steel; M8 x 1.25mm)
• One 2 gram pouch Loctite C5-A Copper Anti Seize
• Easy to follow instructions


Features:
With a class 12.9 rating and a minimum tensile strength of 1220N/mm2 (176,000+ PSI), these extended studs will blow your mind and surprisingly not your wallet!

Just like our popular InoX stainless studs, these feature a 4mm hex drive in the tip which allows installation with nothing more than a mere Allen wrench, how cool is that?

Each Obsidian stud measures 45mm long to allow fitment of aftermarket exhaust manifolds (especially turbo manifolds) and headers that may have a thicker than OEM flange.
On your intake side, these studs will allow for proper installation of heat shielding gaskets like Hondata, Golden Eagle, Bisimoto, and others as these gaskets are much thicker than OEM and can cause fitment issues.

The nuts are crafted with a built in washer that has serrations on the bottom to resist loosening due to vibrations. This built in washer provides the nuts with a larger surface area for greater clamping pressure to insure a tight fit between your manifold or header and your cylinder head. Better clamping pressure insures a tight and leak free fit for years to come and extended gasket life.

Why only a class 10.9 nut, why not a 12.9 or higher?
This is a question that we've been asked on several occasions. By using a lower class nut on the higher class stud, this insusures that in the event the nut needs to be removed or is over torqued by accident, the threads on the nut will be damaged, not the stud. A damaged nut is easier, faster, and cheaper to replace than a stud. We've put a lot of time and thought into the design and development of our kits and we believe it shows!

 

Exhaust Manifold Stud Upgrade

 

I looked at your prior post of that info and looked up the eBay listing for the studs but they were long gone and the ai robots said not to trust eBay hardware. Any suggestions? I have time to order a different stud kit. The one I have is Dorman zink cromate coated steel. Should be fine, better than OEM and stainless which I saw a lot of people on here use.

I saw the OEM manifold flange bolts are about 33mm and have about 13mm of thread engagement with a 20mm++ total threaded hole they go into. I saw a thread where the guy drilled out his bolts straight into the cylinder head lol. The 50mm Dorman product I measured out to something like 16-17mm thread engagement. Still more then necessary and less than the total possible engagement in case i mess things up and have to drill. There’s still be threads left in there and space in the rear to show done if i ever had to drill them out before hitting the cylinder head. There’s still 51mm length will leave the 17mm thread engagement, about 5mm non threaded space where the flange and gasket will be, the rest will be left protruding to hang ect emanifold while fastening and for nut engagement. I think I saw people using about 44mm, probably fine, but low flange hanging for when assembling.