>I'm sure that the 3 carb setup gives more power than the 2 carb because of
>a bit of Jag history.
[bit of Jag history deleted]
>Anyway, the point is that they went from 2 to 3 carb's in one of their
>quests for more power from the engine. If more power could be extracted
>from 2, I'm sure they would have found a way to do it when they were using
>2 on the XK's.
Then there's the other side of the coin. The Big Healey
went from a 2.6L 4 to a 2.6L six (that actually had a drop
in performance, but an increase in smoothness). Then the
3000 (duh, three liters, right?) replaced the 100-6 and
things started looking up.
The 3-liter Big Healey six was originally offered with two
SU carbs. In 1962, it was upgraded for a short period of
time to a triple. This model, the BT7, was a four-place
roadster body (side curtains, removable hood, er, top) with
three SU carbs (of a size that escapes me... I seem to think
they were 1 3/4"). (There were a very few BN7s, two-seat
roadsters, made with the tri-carb setup. At least one was
used by Hollywood Sports Cars in the sixties to take the
SCCA production racing championship three years running,
with an engine set up by Doane Spencer, who also set up
Hollywood's E Production winning MGB and their B Production
winning Sunbeam Tiger.)
The power was up from the twin of the previous year, but
there were lots of complaints from people who were having
trouble keeping them synchronized. So the BT-7 was replaced
with a twin-carb version which, and again my memory is
not precise here, used two 2" SUs. In any event, the
post-BT7 twin-carb, put out as much power as the tri-carb
but was easier to maintain. Ultimately, the last of the
Big Healeys, the BJ8, was putting out 152 bhp on two 2"
SU carbs. I think the tri-carb was generating something just
on the shy side of 140, stock. Spencer's race motor, for
what it's worth, put out over 200 bhp. A modern vintage-race
Big Healey with the 6 can pump out really huge amounts of
power, using the factory Weber setup (which only works on RHD
cars because of clearance problems with the linkage) or with
a new one (made to clear the steering column on LHD cars).
Of course, Webers don't count in the multiple-carb concern.
A good DCOE Weber setup uses a separate choke for each port,
and ignores the problems (BMC A and B series engines excepted)
of conflicting pulses coming back out the intake manifold.
The only vehicle I've ever driven with triple Webers was my
Lotus Cortina, and that was a hell of a setup -- two Webers
under the hood, and one in the trunk! Of course, the one in
the trunk burned charcoal... :-)
--Scott
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