Hi, Larry Pitts!
Caught your post while attending recurrent ground school, studying for
my
6 check and transferring from BOS to JFK
which will be my domicle for the next year or so though I may find
myself in LAX and
living in San Diego by the end of 2002; we'll see! Very "busy" period
but your post
caught my interest.
Regarding your choice of 45 DCOE or HS2's----. I have experience in
(BTDT)
these matters, so, for what it is worth:
45 DCOE kits come tuned for the stock
1275 and they work very well. The performance boost in the stock motor
consists mainly of better (faster) response
off the line. Once at speed, you will notice
very little difference between the carbs, if any at all. The SU's will
probably deliver
better fuel economy, in any event, along with care-free all around
driveability without "dynoing" or "dialing in".
Where the DCOE really comes into play
over stock SU's is in "tuned" applications
wherein the head has been modified for
better breathing, cam notwithstanding, and this includes bigger valve
sizes for
both inlet and exhaust, along with a header with tubes sized for the
expected
power produced (erring on the "small" side is wise for the street) along
with a free flow exhaust system of course!
Now add the Kent 266 timing to the foregoing and you've brought the
engine
to the ability of the DCOE to pack in more
air. The DCOE can't do much with the stock state of tune, but it can
sure produce, now! As a matter of fact, you'll
probably have to retune the stock 1275
DCOE settings. Now we get into "dialing in" or "dynoing" for the
application.
Look at any Weber tuning booklet for
45 DCOE settings and compare those
listed for the stock 1275 against those
for the stock 1275 Cooper S and you will understand the effects of
larger valve
sizes and better breathing. To begin with, chokes for the stock 1275 are
34mm;
they are 38mm for the stock 1275 Cooper
S! And this is just the beginning>
Now, the stock 1275 Cooper S went like
a raped ape (relatively speaking) and it
did so on SU's, not a Weber, right?
So the Weber doesn't really have that much over the SU, except maybe in
intitial response off the line.
So, if I were planning a lot of driving wherein intial off the line
response was
a priority, I'd probably go with a 45DCOE.
Were this not the case, I'd go with the SU's for better economy and all
around
driveability. Don't forget, you haven't got
a stock 1275 anymore with the Kent 266
cam, even with stock valve sizes. Most
likely, you'll have to "tweak" the 45DCOE
settings to "match" your application to get
the best from the Weber on your specific
motor. The 266 will give you more mid-range (excellent choice for
highway
use, BTW) and "lower" top end "potential"
in the torque dept. Improper mixture will
negate this to some extent so tweaking of
the Weber settings is almost a must if you
want to get the best out of the cam, stock
valve sizes notwithstanding.
With your engine tune, simply going to an
H6 (or "M") needle (instead of the "leaner" AN) should pretty much
suffice for your application, if you stick with the SU's.
This takes the stock distributor curve into account as well, so no
changes required
in the "timing" department, either.
The DCOE will require a vacuum takeoff or you'll have to block off the
vacuum port
which will have a negative affect on cruise
(highway in consideration of the rpm's you'll be turning with the 5
speed) fuel
economy.
You can also get a little faster response from the SU's by going to a
SLIGHTLY
heavier oil in the chamber (a slightly heavier spring would serve the
same
purpose), assuming "lean" progression
was the culprit considering the "longer"
timing of the Kent 266.
As I said, going with the "rich" SU needle
application for your current SU carb. would probably be all you'd really
need to do with the stock motor incorporating the
Kent 266 timing; nice and easy, eh?!
Of course, you could try both and see which one you prefer, but my bet
is you'll
ultimately choose the the SU's for care-free day to day driveability and
better than reasonably good performance combined with economy of
operation, to boot.
I'd also say that you should keep an eye on the plugs considering you're
doing a lot
of highway cruise but, considering the rpm's you'll be using with the 5
speed, I
do not believe this will be a consideration
as it might with the normal box ratios, using a 3.9 diff.
With my 3.7 diff using the 210 5 speed,
I am doing almost 65 at 3,000rpm with
175/70's, so the motor isn't being at all
"pushed" at normal highway cruise.
Hope I helped rather than confused the issue for you!
Incidentally, as you may know,"fixed choke" carbs can be a real PIA to
dial in, in terms of "progression".
I am replacing the "fixed choke" Holley
on my Judson with a 1&3/4 SU set-up,
accordingly. Same carb. (though slightly
larger) that came with the Shorrocks blower (British "Judson"). Others
using
Judsons have done this also, the most
recent being a buddy in the Netherlands
who got fed up with the Holley's "progression" problems.
Cap'n. Bob
'61 :{)
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