Exhaust Manifold Studs 3/8" UNC x 1.9/16 | Volvo | Qty: 20
- Stud Type: UNC (Coarse)
- Overall Length: 40mm
- Thread Pitch: 3/8" UNC
- Suitable for: Volvo
- Long Lasting & Durable
- Pack of 20
Stud Size & Fit:
These Imperial exhaust manifold studs are for the direct replacement of rusted or damaged studs. Exact fits can be ensured by reviewing the data sheet attached which includes precise stud measurements. Over their lifecycle manifold bolts expand and contract due to exhaust heating and cooling. Over the years they can become worn and damaged and need replacing.
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UNC / UNF Thread Type:
UNC and UNF are the two main categories of unified thread standard. For a given nut size of nominal diameter, Unified Fine Pitch (UNF) and Unified Coarse Pitch (UNC) represent two different thread densities. UNC is the most commonly used. The choice of UNC versus UNF is influenced by the specific application of the job at hand and each type delivers different advantages.
UNC - coarse threads are more durable and have greater resistance to stripping and cross-threading. They are also less susceptible to being nicked or damaged and therefore they do not have to be "handled delicatley" compared to fine thread (UNF) nuts. Coarse nuts install much more quickly and are not not affected by plating buildup to the same extent as fine UNF threads.
UNF - fine threaded bolts are stronger than UNC coarse threaded bolts of the same hardness. This is due to the fine threaded bolts having a slightly larger tensile stress area. Fine threads also have less tendency to loosen under vibration due to the fact that they have a smaller helix angle than coarse threads.
UNF also has the advantage of allowing for finer adjustments in applications that require this characteristic. They can also be more easily tapped into difficult to tap materials and thin walled sections and they require less tightening torque to achieve equivalent preloads to the corresponding UNC nuts/ bolts.
Manifold Stud Degradation:
Manifold studs are exposed to extreme engine temperatures for prolonged periods of time. Removing them can be a near impossible task. Corrosion and rust can fuse the exhaust manifold studs on older vehicles.
Whether it’s to replace the manifold itself or to get at other parts inside your engine the bolts will have to be removed. When your exhaust manifold studs are stuck, try these tricks to get them off.
How To Remove Exhaust Manifold Studs:
Step 1 - Hammer Time
Gentle coaxing with a hammer. A couple of careful firm taps is it all it takes. A gentle hammering should break the seal that rust has created between the bolts and the engine block. Don't hit the stud too hard incase you bend it.
Step 2 - Leverage
When it comes to a stuck nut - it's a good idea to add a length of iron pipe to your wrench for some additional leverage to deliver extra torque. The longer the handle the greater the torque. More torque makes it easier to loosen the stud.
Step 3 - Silicone Lubricant
At this stage it is best to apply some industrial strength Silicone Lubricant Spray. This does a great job on freeing up bolts that have been seized by rust and corrosion. Direct the spray in between the exhaust manifold stud and the engine block. Don't spray the bolt head. For best results you should let the lube get to work over night.
Step 4 - Block Heating
If you experience problems loosening the bolt inside the engine block, then you can try loosening the engine block around the bolt. You can use a hand held torch to heat the engine block around the exhaust manifold. This will expand the stud casing and generate wiggle room. Note, you will need to let the engine block cool before repeating the process for the next bolt.
Step 5 - Fire and Ice
A quicker process involves heating the exhaust manifold bolt itself and then cooling it quickly. You can effect this method by applying a torch directly to the bolt head to heat the stud as rapidly as possible without altering shape. Next apply an ice cube, (using tongs), directly onto the bolt head. Then repeat this with a second ice cube. The rapid loss of heat will result in a contraction/ change of size and break the rust seal that had formed.
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