Can I use Grade 8 bolts on exhaust manifold?
Common practice is to replace the exhaust manifold bolts on ’94 – ’96 cars with Grade 8 hardware. They are hardened and will carry the highest tensile load, which seems to help them withstand the heat cycles the bolts are exposed to.
Can I use Grade 8 bolts for headers?
Agreed. Using grade 8 in a linear clamping application is fine. They are harder and a little more brittle, so shear applications aren’t wise. I’ve hoisted engines with grade 2 bolts, but I’ve had one fall because of a broken grade 8.
What are the different grades of bolts?
There are several grades of bolts but the three common grades for SAE are 2, 5 and 8. The common class (grades) for metric are 5.8, 8.8, 10.9 and 12.9. Each grade has a specific bolt strength. No matter the system used to grade the bolts, the higher the number means the stronger the bolt.
Should I put anti seize on exhaust manifold bolts?
If you are reusing exhaust manifold bolts (which we don’t recommend), apply a metal fortified anti-seize to your manifold bolts. If you’ve just removed the broken bolts and ready to complete the repair, chase the threads clean and use fresh OEM bolts for best results.
Can you use stainless steel bolts exhaust manifold?
There’s nothing wrong with them on exhaust systems but you really can’t put any serious torque on them because they are much lower tensile strength than alloy steel. They will stretch more so have to be tightened more than once after break in (in this application.
Can I use any bolt for exhaust?
the grade of a bolt has nothing to to with what temperature it will hold up to. Grades are a standard of tensile strength. Your exhaust does not require a bolt of even grade 5 strength.
Are exhaust nuts special?
Are exhaust bolts special? Exhausts are not high stress areas so the bolts can be 8.8 or even softer. We used to use brass nuts on exhaust manifolds so the nut could be easily cut off in the unlikely event it seized. Grade 4.6, 4.8 or 5.8 should be all be fine.
What is a Grade 8 bolt?
A grade 8 bolt is stronger than the more commonly used grade 5. It is made of alloy steel and has six radial lines on the top of the bolt head. Grade 8 bolts have a tensile strength of 150,000 pounds per square inch.
What is the difference between 8.8 and 12.9 grade bolts?
The mechanical difference between the 12.9 and 8.8 is yield strength (roughly 90% of 1200 MPa vs 80% of 800 MPa). That means the 12.9 can be stretched further (i.e. torqued to some higher value) before it yields, which of course increases the clamp force.
What is the hardest bolt you can buy?
Commercial-grade 8 bolts are the strongest option available. They’re made from medium carbon alloy steel and have markings that include six raised dashes. The psi of the bolt is 150,000, meaning that it can withstand great deals of pressure because of the way it was quenched and tempered.
What is the yield strength of Grade 8 bolts?
Grade 8 (SAE J429) is a medium carbon alloy steel with one of the highest tensile strengths available. With a minimum tensile strength of 150 ksi and a minimum yield of 130 ksi, Grade 8 has a higher tensile and yield strength than other steel grades such as Grade 5 and B7.
Is Grade 8 or 10.9 stronger?
Class 10.9 is stronger than class 8.8. It is commonly found in high strength automotive applications. Class 10.9 is similar to grade 8. A low carbon steel for general use.
What is the metric equivalent to Grade 8?
Metric Bolt Conversion
| Metric Nut Class | SAE J429 Normally Used | ASTM Grades |
|---|---|---|
| 5.8 | 5 | . |
| 8.8 | 8 | A325,A449 |
| 9.8 | 9 | A193,B7 and B16 |
| 10.9 | 10 or 12 | A490,A354, Grade 8D |
What is the strongest bolt grade?
The strongest commercial-quality bolt is grade 8, marked by six raised dashes; its medium-carbon alloy steel has been quenched and tempered to achieve a tensile strength of 150,000 psi.
What is the difference between a 10.9 and 12.9 Bolt?
12.9 grade steel has 120% of the tensile strength of 10.9 grade steel. The “12” prefix indicates a tensile strength of X100 N/mm^2 and the “9” suffix indicates a multiplier. Both 12.9 and 10.9 have the same multiplier, so the comparison is straightforward: 12 to 10.
Is a 12.9 Bolt stronger than Grade 8?
Many fasteners (screws, etc.), especially smaller sizes, are typically not graded—their strength isn’t specified….Table 1.
| Grade/Class | Strength |
|---|---|
| Metric Class 8.8 | Similar to Grade 5. |
| Metric Class 10.9 | Similar to Grade 8. |
| Metric Class 12.9 | The highest metric class for strength, it exceeds Grade 8. |
Are stainless bolts stronger than Grade 8?
Stainless commonly comes in grades 18.8 (304) or T316. Stainless steel bolts are rated for corrosion resistance. A stainless steel bolt has the same PSI rating as a grade 5 bolt (125,000 PSI). A grade 8 bolt has a stronger rating with a PSI of 150,000.