Exhaust Manifold Questions

(EDIT: Car is a 1992 LX convertible, 2.3L N/A)

Hello again friends!
I have been struggling to remove my pesky O2 sensor for a couple of weekends now, and at some point I decided that it would be significantly easier to get the O2 sensor out if I just remove the Exhaust manifold completely to do it. The manifold probably needs a cleaning, a new gasket, and a new coat of paint anyways so why not. However, in doing research on the hardware and tools required, I have run into a wall. I can’t find a solid answer anywhere about what types of bolts and studs are holding this thing in. I read somewhere that the regular mounting bolts are M10-1.50, but the poster did not mention a bolt length. I haven’t found anything solid on the type of studs that are used, will M11-1.75 x M12-1.75 x 65mm studs work for those? What kind of bolts are used on the flange connecting the manifold to the exhaust pipe? In order to get the correct thread chasers/tappers, I need to know the bolt and stud types for everything. also, will an M18 x 1.50 thread chaser work for the O2 sensor bung threads? Thank you for any information, I don’t really want to go pulling these bolts and studs out before I know where I can get new ones, so I turn to you all for some more help.

KingSaturn said:

Hello again friends!
I have been struggling to remove my pesky O2 sensor for a couple of weekends now, and at some point I decided that it would be significantly easier to get the O2 sensor out if I just remove the Exhaust manifold completely to do it. The manifold probably needs a cleaning, a new gasket, and a new coat of paint anyways so why not. However, in doing research on the hardware and tools required, I have run into a wall. I can’t find a solid answer anywhere about what types of bolts and studs are holding this thing in. I read somewhere that the regular mounting bolts are M10-1.50, but the poster did not mention a bolt length. I haven’t found anything solid on the type of studs that are used, will M11-1.75 x M12-1.75 x 65mm studs work for those? What kind of bolts are used on the flange connecting the manifold to the exhaust pipe? In order to get the correct thread chasers/tappers, I need to know the bolt and stud types for everything. also, will an M18 x 1.50 thread chaser work for the O2 sensor bung threads? Thank you for any information, I don’t really want to go pulling these bolts and studs out before I know where I can get new ones, so I turn to you all for some more help.

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So, I just checked the bolt heads with some sockets and the mounting bolts are 13mm, I checked one of the stud bolts and I think it’s a 15 mm, but I’m not sure if the others are the same as I need to get a metric set of deep sockets to truly check them. I’ve been soaking all of the bolts with WD-40 nightly this week, so I’m debating on just pulling a stud and a bolt and trying to figure out their sizes that way, but I’m hesitant in case they are hard to come by. Does anybody have any information on the stock 2.3L exhaust manifold hardware? If I do figure out their sizes, I will be sure to post everything I find out here for anybody else who is looking for the same info.

KingSaturn said:

So, I just checked the bolt heads with some sockets and the mounting bolts are 13mm, I checked one of the stud bolts and I think it’s a 15 mm, but I’m not sure if the others are the same as I need to get a metric set of deep sockets to truly check them. I’ve been soaking all of the bolts with WD-40 nightly this week, so I’m debating on just pulling a stud and a bolt and trying to figure out their sizes that way, but I’m hesitant in case they are hard to come by. Does anybody have any information on the stock 2.3L exhaust manifold hardware? If I do figure out their sizes, I will be sure to post everything I find out here for anybody else who is looking for the same info.

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I decided to pull one of the mounting bolts out. Here’s what I found after measuring with calipers:

Major Diameter: 10.38mm / 3/8”
Shank Diameter: 10.39mm / 3/8”
Thread Pitch : 1.5mm / 18 TPI
Bolt Length: 54.13mm / 2 2/16”
Bolt head: 13mm / 1/2” socket
Bolt type: flanged

Bolt size: 10m x 1.5 x 54 or 3/8” - 18 x 2 2/16”

I don’t have measurements for the studs yet, they will have to wait until I pull the manifold off, I think they are pinned between the block and the manifold, but I still want to try to replace them as well. When I get to that step, I will post my findings here. I hope this information helps somebody. As far as I know, these mounting bolts are stock. I’m not sure I will be able to find an exact copy, I will try to find one with the correct diameter and TPI, since a washer will make up for a small difference in length.

85GTStangGuy said:

According to a post in another thread, he has a '92.

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Sorry! Yes, it’s a 1992 2.3L LX convertible. Not a turbo.

AeroCoupe said:

If they all come out and look good then just chase the threads with a die and reuse them. Not sure what you would gain getting new ones. As far as I know they are not torque to yield.

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Okay, I’ve read that manifold bolts often mar when you take them out due to the many heat cycles they’ve gone through, and that if you reuse the old ones they may crack from the stress. Does the 2.3L just not get hot enough for that to be a problem? Should I chase the female threads as well?

Noobz347 said:

I personally, would replace them and chase the threads.

I like the ARP 12-point bolts for the exhaust. They're easier to get a wrench and torque on.

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this is what the Haynes manual says to torque the different bolts to, should I follow this then? Should I put anti-seize on the mounting bolts? What kind of bolts are on the flange from the manifold to the pipes?

Noobz347 said:

Yes, you should follow it. If you do end up ordering something like ARP bolts, note that their provided instructions supersede anything you will find in a manual.

Additionally, you should review the bolt instructions when you order to ensure you also get their recommended thread lube [if] required.

Otherwise, I would use the recommended thread sealant, etc...

On the anti-seize specifically? In the areas you have shown images of that are [not] exhaust bolts, I would opt for Blue Lock-Tite. A lot folks don't realize that it also helps keep corrosion in check.



I really have no idea but when I search ARP, I come up with these for the collector:

The Official ARP Web Site | Exhaust Collector Bolts

arp-bolts.com

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Do you know the size of those ARP bolts? Will they work as is for the 2.3? They are listed for the 5.0L, if they are the same then I may go for them. As far as the studs go, I think I’m just going to chase the exposed threads and replace their nuts, I don’t need to remove them to get the manifold off so I don’t really see a point in taking them out. Thanks for your help!