> BTW, when I reassembled the 1500 for my 65 Spit, I used AN grade BOLTS
> purchased from Pegesus Racing, instead of studs. Now I know the stud theory,
> "Put the torque on the top stud threads, not on the threads on the bock".
> But where are nearly all engines other than BMC and Triumph assembled with
> BOLTS?
> Did the Brit engine mfgrs not bother to tap a few extra threads into the
> head? Was it a matter of being able to use a lower quality material by going
> with studs? Anyway, the real question is what will happen to my motor? (I
> uses good lube on the bolts). I noticed the Brit Ford Kent motor in the
> Capri uses BOLTS.
>
> Your thoughts appreciated.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Thanks for the vote of confidence, "Your thoughts appreciated." Actually, a
lot of people slam all things British, but in my experience the materials
used in the construction of our beloved British cars for the most part is of
very high quality. That's one of the reasons it's so expensive to
re-manufacture many of the critical parts. Most of our engines, and
drivetrains are very small, and highly stressed requiring very high quality
materials to withstand the use they were designed for. (Or probably more
realistically they were pressed into service for) A good example is the
rear end in my 72 Spitfire, I doubt there are many rear ends, with the
exception of the 9 inch Ford, or the big Mopar, and Gm units that will
withstand roughly three times the HP they were designed for without self
destructing. Yet I have used this same, very tiny differential for quite a
few years now, and not always gently. It hasn't let me down yet.
But to your question about bolts vs. nuts. Nothing wrong with head bolts,
many engines use them. My V6 does, as well as my Courier. Sure makes head
removal a LOT easier. Probably cheaper in the long run also (assembly,
stock reduced number of parts). But studs are better. The reason is that a
bolt, by it's nature has a high concentration of the stress, when tensioned,
at the junction of the head/shaft. So in a highly stressed condition (head
bolts, rod bolts) you have to use a very high grade to withstand this
stress. A stud/nut combination on the other hand has the stresses
distributed along a series of threads (ideally along the full length of the
threaded area, but in actuality a few threads take most of the load) In any
case the stresses are distributed over a 'larger' area instead of being
concentrated in one localized spot (I hope this is making some sense) This
tends to distribute the loads better leading to reduced failure. Most rod
or head bolts are of grade 8 or better, while your stud/nut combination can
probably get by with grade 5. It's still interesting to note that for a
given grade, the stud/nut combo is always a stronger choice than the bolt-
(by the way, a little touch up paint and you won't be able to tell, it was
either that or pull the engine - I have my limits! :-))
Barry Schwartz
Bschwartz@encad.com (work)
Bschwart@pacbell.net (home)
(San Diego)
70' Spitfire (under-going major surgery) , 72'-V6 Spitfire (daily driver)
70'GT6+
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