Headers Install - frozen "nuts"

[1schoir]

Is there a downside to replacing the stock bolts that hold the exhaust manifold flange to the cylinder head with studs?

Installing a set of headers on my '97 Boxster and I found a number (4) of frozen bolts which snapped off, three of which ended up almost flush with the cylinder head. After MUCH effort and the use of a number of methods, I succeeded in either extracting the remnants of the bolts and/or tapping in new threads.

After reading a few articles on "The Art of Bolt Extraction" :eek: I learned that studs, by their design, are inherently stronger. It seems that when torque is applied to tighten down a nut on a stud, the threads inside the head are not under as much "pressure" as they are when a bolt is tightened.

Coupling the idea of studs with brass metric nuts would make for a much more pleasant experience in the future for another header/exhaust manifold install.

The only downside I can think of is that the studs would interfere with milling of the surface on the head if it is found to not mate up correctly with the flange on the exhaust manifold or header.

Wondering if there are any other issues anyone can point out with installing studs in place of the M8 X 1.25, 28mm long bolts that come stock.

Regards, Maurice.

[1schoir]

Is there a downside to replacing the stock bolts that hold the exhaust manifold flange to the cylinder head with studs?

Installing a set of headers on my '97 Boxster and I found a number (4) of frozen bolts which snapped off, three of which ended up almost flush with the cylinder head. After MUCH effort and the use of a number of methods, I succeeded in either extracting the remnants of the bolts and/or tapping in new threads.

After reading a few articles on "The Art of Bolt Extraction" :eek: I learned that studs, by their design, are inherently stronger. It seems that when torque is applied to tighten down a nut on a stud, the threads inside the head are not under as much "pressure" as they are when a bolt is tightened.

Coupling the idea of studs with brass metric nuts would make for a much more pleasant experience in the future for another header/exhaust manifold install.

The only downside I can think of is that the studs would interfere with milling of the surface on the head if it is found to not mate up correctly with the flange on the exhaust manifold or header.

Wondering if there are any other issues anyone can point out with installing studs in place of the M8 X 1.25, 28mm long bolts that come stock.

Regards, Maurice.

Found a source for the all the needed metric hardware...Still on the fence as to whether to go with the studs conversion.

Regards, Maurice.

[wvicary]

I would do it. Many makers use studs for the exhaust system with copper nuts or jet nuts. I see no problems in converting to this set up. I also use a high temp anti seize compound. The only caveat is to make sure the stud is correctly seated in the cylinder head and I can recommend purchasing a pawl type of stud installer/remover that won't damage the threads during installation. They are also referred to as a wedge type.

[Paul in WI]

Perhaps there will be an issue when installing the headers with the studs already in place.

[1schoir]

I would do it. Many makers use studs for the exhaust system with copper nuts or jet nuts. I see no problems in converting to this set up. I also use a high temp anti seize compound. The only caveat is to make sure the stud is correctly seated in the cylinder head and I can recommend purchasing a pawl type of stud installer/remover that won't damage the threads during installation. They are also referred to as a wedge type.

Vicary:

Thanks for the information of the stud remover/installer. I was going to use two nuts backed up against each other, but now will get the tool to insure against damaging the threads. I had no idea there was such a tool!

Thanks again.

Regards, Maurice.

[1schoir]

Perhaps there will be an issue when installing the headers with the studs already in place.

Paul:

There is plenty of room if the studs are already in place. No interference anywhere that I can see.

When doing the job by myself under the car, I learned that the exhaust manifold gaskets are a pain to keep in position as you try to get the first two bolts started into their threads. Studs might make it easier as they would hold the gasket in place and one person can then easily slip the headers (or exhaust manifold) onto the studs.

Regards, Maurice.

[Jinster]

 What did you end up doing Maurice?

Did you convert to the stud and nut setup (if I understood it correctly)?

And did the header make much of a difference? I have had a set of eBay headers with me for almost 3 years now. Haven't got around to installing them.

[catmanluge]

There should be no problem using studs as there is plenty of room under the motor. If you apply heat to the bolt before attempting to remove it you may have better luck with less breakage.

What did you end up doing Maurice?

Did you convert to the stud and nut setup (if I understood it correctly)?

And did the header make much of a difference? I have had a set of eBay headers with me for almost 3 years now. Haven't got around to installing them.

[1schoir]

What did you end up doing Maurice?

Did you convert to the stud and nut setup (if I understood it correctly)?

And did the header make much of a difference? I have had a set of eBay headers with me for almost 3 years now. Haven't got around to installing them.

Jinster:

It's one of the things that I have not gotten around to completing yet. I did buy the stud installer tool (thanks, wvicary), and I was able to source coated metric studs of the correct size, along with phospor-bronze lock washers and brass nuts.

I may try to do it before the temps get too cold around here. I was under the car a couple of weeks ago and I noticed that the heads of the brand new OEM bolts that I had used to "temporarily" install the new headers looked VERY rusty.

Here is what they look like now, about six months after install, with only about 3,000 miles driven mostly in the spring and summer:

My exhaust definitely sounds much nicer, but it's hard to tell how much is attributable to the headers because I installed a PSE at the same time.

Here is a pic of what they looked like at the time of the install:

Here is a pic of the PSE:

I'll post some pics after I do the stud install, but it may not be until springtime.

Note that if the bolts are original and have never been removed on an older Boxster, it is not a procedure for the faint of heart. If you want to see what I went through, let me know and I'll dig up a link to the saga.

Regards, Maurice.

[Nitro]

Is there a downside to replacing the stock bolts that hold the exhaust manifold flange to the cylinder head with studs?

Installing a set of headers on my '97 Boxster and I found a number (4) of frozen bolts which snapped off, three of which ended up almost flush with the cylinder head. After MUCH effort and the use of a number of methods, I succeeded in either extracting the remnants of the bolts and/or tapping in new threads.

After reading a few articles on "The Art of Bolt Extraction" :eek: I learned that studs, by their design, are inherently stronger. It seems that when torque is applied to tighten down a nut on a stud, the threads inside the head are not under as much "pressure" as they are when a bolt is tightened.

Coupling the idea of studs with brass metric nuts would make for a much more pleasant experience in the future for another header/exhaust manifold install.

The only downside I can think of is that the studs would interfere with milling of the surface on the head if it is found to not mate up correctly with the flange on the exhaust manifold or header.

Wondering if there are any other issues anyone can point out with installing studs in place of the M8 X 1.25, 28mm long bolts that come stock.

Regards, Maurice.

Found a source for the all the needed metric hardware...Still on the fence as to whether to go with the studs conversion.

Regards, Maurice.

Maruice,

Did you ever install the stud conversion? Are you willing to share your source for all the hardware needed? I'm about to tear into a header replacement project and I'm trying to get all the information and parts I need ahead of time.

Thanks,

Nitro