Exhasut Flange Fasteners

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On my 99 Toyota Avalon, the flanges connecting exhaust manifold and downstream pipe has two studs (same as manifold to head)screwed into the upstream flange. The downstream flange is clamped with non-reusable nuts which screw onto the studs. Apparently this is a super duper high strength fastening system required for exhaust service. However, I was wondering what would be wrong with using a couple stainless bolts with lock washers. Believe I could get grade 8.8 at my local hardware store. Not as strong as the factory studs, but maybe strong enough. What do you thin? Thanks.
 
Grade 8 bolts snap under heat, grade 5 bolts stretch. If u plan on keeping the car another 16 years go with stainless or grade 5 which is probably what the factory bolts are.
 
Why not replace the nuts, even if with regular ones? But to answer your question, it should be fine.
 
Originally Posted By: The_Eric
Why not replace the nuts, even if with regular ones? But to answer your question, it should be fine.


I removed the studs to facilitate reassembly. Factory studs and nuts are cheap and available. Just thought the bolts would be an easier install.
 
Originally Posted By: krismoriah72
Grade 8 bolts snap under heat, grade 5 bolts stretch. If u plan on keeping the car another 16 years go with stainless or grade 5 which is probably what the factory bolts are.



Don't know about factory but Dorman aftermarket are M10.9 roughly the same as SAE Gr8. The M8.8 at the hardware store are roughly the same as SAE Gr5.
 
Stainless on stainless will gall and seize with the exhaust manifold heat. I use SS threads and regular hardened nuts. That way the threads stay good and you can get the nut off though you will probably need to replace them.

On my Hyundai Genesis Coupe the exhaust manifold is SS and they used SS studs with ss nuts. Strips almost every time someone needs to remove the turbo.
 
If you run studs and the studs sieze, you can get the manifold off via the nuts, assuming you don't loctite them in place.

On my saturns I've had 50/50 odds of the stud coming out with the nut, or not. But am glad I have options. They slather everything in never-sieze.

Studs are theoretically better because you can drive them home into your solf aluminum head without a load stressing/ stretching them and having their threads carve through something expensive. Then, as a unit, the stud holds the load as the nut clamps down.
 
Originally Posted By: eljefino
If you run studs and the studs sieze, you can get the manifold off via the nuts, assuming you don't loctite them in place.

On my saturns I've had 50/50 odds of the stud coming out with the nut, or not. But am glad I have options. They slather everything in never-sieze.

Studs are theoretically better because you can drive them home into your solf aluminum head without a load stressing/ stretching them and having their threads carve through something expensive. Then, as a unit, the stud holds the load as the nut clamps down.


I am talking about the manifold to pipe connection, not the manifold to head connection.
 
Originally Posted By: SHOZ
Stainless on stainless will gall and seize with the exhaust manifold heat. I use SS threads and regular hardened nuts. That way the threads stay good and you can get the nut off though you will probably need to replace them.

On my Hyundai Genesis Coupe the exhaust manifold is SS and they used SS studs with ss nuts. Strips almost every time someone needs to remove the turbo.


Won't be stainless on stainless. The stainless bolt will screw into the threaded steel flange.
 
Originally Posted By: artbuc
Originally Posted By: eljefino
If you run studs and the studs sieze, you can get the manifold off via the nuts, assuming you don't loctite them in place.

On my saturns I've had 50/50 odds of the stud coming out with the nut, or not. But am glad I have options. They slather everything in never-sieze.

Studs are theoretically better because you can drive them home into your solf aluminum head without a load stressing/ stretching them and having their threads carve through something expensive. Then, as a unit, the stud holds the load as the nut clamps down.


I am talking about the manifold to pipe connection, not the manifold to head connection.


Same premise, if you're driving in to "something tapped" that's at all fragile/ sensitive/ hard to re-tap, and cost isn't the ultimate driving factor, go with studs & nuts.
 
Note that most "copper nuts" are actually copper coated steel.

They should be replaced each time since the copper plating is thin and usually badly damaged during removal.
 
Originally Posted By: eljefino
If you run studs and the studs sieze, you can get the manifold off via the nuts, assuming you don't loctite them in place.

On my saturns I've had 50/50 odds of the stud coming out with the nut, or not. But am glad I have options. They slather everything in never-sieze.

Studs are theoretically better because you can drive them home into your solf aluminum head without a load stressing/ stretching them and having their threads carve through something expensive. Then, as a unit, the stud holds the load as the nut clamps down.


Gotcha. I installed new factory studs and non-reusable nuts. Turns out I made a mistake by removing the original studs because the difficult fit was caused by the slip joint design of the flange, not the studs.
 
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