Hi Darrell.
Recently my brand new copper clad exhaust TR6 manifold studs stripped as I
was installing them. This led me to ask a lot of people questions about
studs and fasteners.
I am told that the main reason for using studs is that you don't want to run
the risk of stripping the holes in your block or head. All of the heavy
tightening is done on the stud.
Another controversy was about installing the studs themselves. Do you
tighten them with a jam nut or not? The answer is no. You want all of the
load on the top of the stud threads and the bottom of the hole threads.
Tightening the studs up against the unthreaded part or bottoming it out
would prevent this.
Another interesting fact is that most of the load is borne by the first two
threads. The rule of thumb is 1.5 x the fastener diameter.
Why aren't the studs threaded all of the way? One answer is cost. Another is
that the unthreaded part serves as a pilot to locate the manifold properly.
By the way. As a replacement for the stripped manifold studs, I used studs
threaded end-to-end. These worked fine. They were the studs which hold the
clamps rather than going through the manifold flange, so weren't needed as a
pilot.
One local parts guy told me that he used socket head screws on his TR6
manifold. He said they are easier to reach. Provided you measure carefully
so that they don't bottom out, this will work fine.
- Hugh
>
> Is there any technical reason to prefer a stud over a bolt
> (or vice versa)?
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