Exhaust Manifold Stud and why LR did this?

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Barbados

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Hi Guys, been working on my 110 Rebuild on and off and back at it again, this time until its complete, a few more months I hope.

While working on my turbo adapter etc, I wondered why Land Rover only has 13mm of threads on the exhaust manifold stud, fitted into the head which has 26mm depth of female threads. Then on top of that, a huge length of the stud extends on the manifold side, when just 10mm is required for the nut. I do not think their idea of this extra length, is to facilitate 2 nuts for installing or removal of the studs.

It just seems like LR have this back to front. Logically one would expect that since the head is aluminum, you will want to maximize the thread depth and surface area to avoid stripping the aluminum threads and then have enough threads for the nut. I know with the correct tightening torque, the threads will not strip nor should the aluminum have a raised gasket surface, but why LR did it this way.

I will be boosting the engine a bit more and would want a good exhaust and intake seal, I bought some grade 10.9 studs (yea I know its an over kill) to replace the original studs. I am thinking of fitting them the other way than how LR did it, whats your thoughts..see pic please.
 

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how thick is the manifold+gasket+nut?
About 1.8CM. The studs have more than enough length and threads to accommodate the manifold, gasket and self locking flange nut. I will use the grade 10.9 new studs and nuts I bought, they have to be cut, but the shoulder and length will be perfect for the manifold, I will use those instead.
 
I just used the Wurth Studs holding up well.

Fair point
Those are ideal, not sure if I can get them here, might have to import. They will probably be better than what I bought since they will have the tensile strength but yet allow for expansion. Sometimes stronger is not better when some flexibility is needed, between two different metals which has to endure heat.
 
Very much so.

They are rolled so rather strong and come with copper flashed nuts for easy removal.

They are about £15 over here, if you have trouble getting someone to ship them, have them send to me and ill forward on if need be.
 
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