Interesting thread in certain respects, but possibly better to know the
actual motivation for the actual build of these 86 cars with apparently 9:1
cr engines? Were they “stock” built looking for an eventual purchaser,
special order for a knowledgeable buyer who had genuine intentions to race
or by a boy-racer on public roads (either is OK), or just a well healed
customer ticking all the options boxes not really knowing what they were
actually buying. I suspect an element of all of these.
I cannot say from first hand-experience of a 9:1 cr XK140 engine, but do
have lots of real world experience with E-Types with 9:1 cr, and my
consistent advice to anyone rebuilding an E-Type engine is to fit 8:1 cr
pistons due to lack of readily available 99 octane fuel. WE have discussed
different conventions re Octane Rating, so my comments relate to general
UK/Australian Octane ratings - and E-Type with 9:1 cr was designed to use
100 octane fuel, or 5-Star in UK, although 99 octane was quite OK in
every-day use. Once you get below 99 octane some cars start having
problems, and below 98 octane all 9:1 cr engines have problems, and
certainly today in Australia 92 and 96 Octane are the most readily available
fuel, with 98 octane reasonably available but at a huge premium. 99 or 100
octane is not available without using fuel-additives (expensive and
inconvenient) or access to aviation fuel (expensive and very inconvenient).
Thus my advice to rebuild E-Type Engines with 8:1 pistons that will then
happily run on 96 octane on an everyday basis, at the expense of 5 bhp if
indeed the car is ever driven at 5500+ rpm. Loss of mid range torque is
indiscernible on the road.
So in the 1950s - who would deliberately want a 9:1 cr XK140. In Australia,
most new Jaguars were supplied with 7:1 cr engines, with the occasional 8:1
cr due to our then crap fuel quality - don’t know about USA clearly with
better fuel than us given 8:1 cr was the norm, but could you readily get
99/100 octane fuel in the US in 1950s?
S800040 - sold new in Australia specifically to race, was run on specially
sourced “racing fuel” (aviation fuel), and not from the driveway pump. Now
rebuilt and restored to Concours winning condition, but with 8:1 cr pistons.
Why on earth would as Terry advises, there be three XK140s built/sold with
9:1 cr pistons but using A-Type heads, and not the more efficient C-Type
heads readily available. Makes absolutely no “technical” sense at all,
which makes me think this must surely be an error in the records Terry got
this information from. Or a salesman, who got the order WRONG - rather
than for extra commission - as if commission was the motivation then surely
the XK would also have a C-type head.
Not to the same extent - but you also have to wonder why 21 cars with 9:1 cr
had OVERDRIVE. This very much sounds like wealthy customers ticking all
the option boxes regardless of the technical implications. If you went
racing - and happy to put up with the fuel demands of 9:1 cr - you most
certainly did not want OVERDRIVE. Maybe for some specific long-distance
“touring” events, but even S804231 - the works prepared FHC that ran at 1955
Le Mans had neither OVERDRIVE, nor a 9:1 cr engine, but did have H8
carburetters and twin coils.
Also the issue of “close ratio” gearboxes is an interesting one - not
necessarily a good choice, even if racing. Depends a lot on intended
specific use, thus it was a rare technically-deliberate option. Even the
above specifically ordered for racing S800040 - with no overdrive, 9:1 cr
engine, and with H8 carburetters, did not have a “close-ratio” gearbox.
There are many who think that standard gearbox ratios, and no-overdrive
actually gives you the best all-round gearing package - such is the beauty
of the various packages and options offered by Jaguar. Overdrive is great
for steady-speed highway cruising where fuel-economy is a priority.
Other than finding out how many of the 86 cars built new with 9:1 cr do
indeed survive, more interesting would be how many of these survivors still
in fact have 9:1 cr pistons fitted, and have not been rebuilt with 8:1 cr
pistons.
Personally, I accept the relative pros and cons of H8 carburetters mean
different conclusions to different people (I would like a set on the wall,
but not on my XK140), but off hand, cannot think from a technical/driving
perspective any merit in having 9:1 cr pistons still fitted - unless you
actively and regularly race - and then would probably have a full race
prepared non-original engine anyway. But happy to have a current
owner/driver advise otherwise.
In my data base, I list only 18 XK140 Engines with -9 cr engine numbers.
How many of these still have 9:1 pistons is anyones guess. All current
survivors, but still only a small percentage of 86 built - if indeed that
count is correct. No names/owners mentioned, but anyone on list can reveal
their hand if they want to.
SEVEN OTS as follows:-
G3704-9S
G7789-9S
G8399-9S
G8918-9S
G9173-9S
G9208-9S
G9590-9S
EIGHT FHC as follows:-
G2249-9S
G3136-9 (no “S” suffix, but Chassis is “S” prefix so an error ???)
G4920-9S
G7830-9 (no “S” suffix, no “S” prefix to Chassis Number - as above, surely
NOT)
G9166-9S
G9399-9S
G9424-9S
G9525-9S
THREE DHC as follows:-
G2258-9S (not original engine to Chassis recorded, don’t record original
chassis number so may not have been a DHC originally)
G7801-9S
G8725-9 (no “S” suffix, and no “S” prefix to Chassis Number)
I had no record of 819014DN/ G8646-9 but apart from anomaly of a -9 cr
engine with an A-Type head, engine number is also out of sequence for
October 1956 build-date?
Similarly, I have no record of S813150/ G9828-9S that Terry notes as being
in USA - but nothing unusual about numbers for January 1957 build-date.
So that gets us up to 20 known survivors - where are all the others?
Roger Payne - XK140MC OTS; E-Type 4.2 S.1 OTS; DSV8.
Canberra.-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Terry McGrath
Sent: Friday, 13 May 2011 3:36 AM
To: xk@jag-lovers.org
Subject: [xk] XK140 9-1 register
XK 140’s with 9:1 compression:
86 cars were built of which 3 where non MC cars 21 cars had Overdrive.
There is no pattern as to batches of engines or chassis numbers of cars that
had 9-1 motors so it would appear to be only as a result of customer/dealer
order. Although 34 cars where in the 9000 series of engines.
It would be nice to get a list to gether of surviving cars.
Where I mentioned 2 inch Sand cast carbs this is where it is known the car
was fitted from new with 2 inch H8’s
Chassis: S800040 G3704-9S 2 inch H8 Australia
Chassis: S804366 G4920-9S Australia
Chassis: S 812628 G8399-9S 2 inch H8 USA
Chassis: 819014DN G8646-9 USA not an MC car so
there are 9-1 standard cars!
Chassis: S815894 G9424-9S 2 inch H8 motor terry mcgrath
Australia, car also in Australia
Chassis: S813024DN G9590-9S Dave Shaw
Chassis : S813150 G9828-9S USA
There is something to these cars as one I have details of is noted in
factory records as competition clutch, CR gearbox, 3.77 axle and .006 and
.010 valve clearances which is definetly not standard XK140 stuff and is a
car that was intended to be raced
terry mcgrath
Jaguar XK120 book
Sample Pages at http://www.jtpublications.com.au/book/
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