Exhaust manifold bolts questions
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Senior Member
Joined: Oct 2011
Posts: 1,655
From: Wisconsin
Exhaust manifold bolts questions
Is the pitch 8M 1.25? Proper pitch?
Will the Dormand 03411 (10.9) work?
https://www.dormanproducts.com/p-274-03411.aspx
Is there a gasket you'd recommend? Why?
Gonna need to remove 3 broken bolt minimum.
Will the Dormand 03411 (10.9) work?
https://www.dormanproducts.com/p-274-03411.aspx
Is there a gasket you'd recommend? Why?
Gonna need to remove 3 broken bolt minimum.
Last edited by Happy Hummer; Apr 10, 2024 at 01:07 AM.
Thread Starter
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Senior Member
Joined: Oct 2011
Posts: 1,655
From: Wisconsin
Well, Lol! Went and did a bit more research and these are the part #'s I'm coming up with.
Exhaust Manifold Part# GM 12655844
Proper pitch and length of Exhaust Manifold Bolts 8M 1.25 by 56-ish
Please do let me know if these are possibly incorrect.
Exhaust Manifold Part# GM 12655844
Proper pitch and length of Exhaust Manifold Bolts 8M 1.25 by 56-ish
Please do let me know if these are possibly incorrect.
Senior Member
Joined: Jul 2012
Posts: 8,999
From: C-Town
10yrs ago still sealed tight!
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!
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!
Thread Starter
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Senior Member
Joined: Oct 2011
Posts: 1,655
From: Wisconsin
Exhaust Manifold Part# GM 12655844
Exhaust manifold Flange Gasket donut/ring Part#15105884
Exhaust manifold Flange Gasket donut/ring Part#F32146 (HummerZ recommended)
Dormand 03411 (10.9 tensile strength)(M8 1.25 55.5) steel
The one HummerZ offered are of equivalent quality for gasket and ring. The Dorman bolts are one step down but are 10.9
Last edited by Happy Hummer; Apr 10, 2024 at 01:06 AM.
Super Moderator
Joined: Jul 2007
Posts: 13,090
From: Boat Town USA MI
Nerd warning.... Metric 10.9 does not measure "hardness". It is a measure of tensile strength and yield strength combined. 10= Tensile 1000 MPa/ 9= yield 90% of 1000 MPa, hence 10.9
SAE Grade 8s are actually similar in hardness, but offer greater tensile and yield strength.
Use anti-seize on the treads going in the head.
SAE Grade 8s are actually similar in hardness, but offer greater tensile and yield strength.
Use anti-seize on the treads going in the head.
Super Moderator
Joined: Jul 2007
Posts: 13,090
From: Boat Town USA MI
Grade 8 would work if you cannot find the 10.9 replacements. My rule of thumb is grade 8s on the exhaust system itself (flange and collectors), but OEM for what bolts to the engine. Never had any issues following that yet.
Senior Member
Joined: Jul 2012
Posts: 8,999
From: C-Town
