[xk-engine] boring out a 3.4 to 3.8

In reply to a message from Mark Eaton sent Wed 9 Dec 2015:

This statement is only partly correct . An engine producing
good torque at low rpm will not only be an advantage if the
shift point is at low rpm : it will be an advantage at all
times that the engine is passing through the relevant ‘‘fat
torque’’ rpm band . It is correct, however, that there will
be some loss of performance at high rpm, but this is usually
of less consequence in a road car . Incidentally, the B type
heads were devised to maximise torque in the low to mid rpm
range i.e. between about 1500 and 3500 rpm and the peak of
the torque curve was at 3000 rpm. The B heads were designed
to give good performance with the BW DG box introduced about
the same time . The straight port heads with 3 carbs and
the cams used gave a torque peak at 4000 rpm, and from
memory with 2 HD8 ( on the XJ6) gave a peak slightly lower
than that, say 3750 rpm–
The original message included these comments:

An engine that produces more torque at lower revs will win the day only if
the driver shifts at those low revs … which may well often happen driving
around town, but will likely be less effective during ‘‘spirited driving’’ on
a back country road or race track.


christopher storey
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//please trim quoted text to context only

In reply to a message from christopher storey sent Sat 12 Dec 2015:

I take your point (although the XJ used HS8s). But the
3/8’’ XK cams were essentially the same from about 1953/4
to 1992 and the biggest car of all (almost universally
using a slushbox) was the straight port three-HD8 MkX.–
The original message included these comments:

the torque curve was at 3000 rpm. The B heads were designed
to give good performance with the BW DG box introduced about
the same time . The straight port heads with 3 carbs and
the cams used gave a torque peak at 4000 rpm, and from
memory with 2 HD8 ( on the XJ6) gave a peak slightly lower
than that, say 3750 rpm


1E75339 66 D, 1R27190 70 FHC, 79 S2 XJ12L
Gaithersburg, Maryland, United States
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//please trim quoted text to context only

Mike, I bought the “new” rod cap bolt and self locking nuts from Welsh for my 3.8 E Type. Now I’m wondering if the new self locking nuts have a different torque setting. Have you used the new style bolts and nuts and is there anything I should know?

thanks,