Wow, I knew that you all would be great help! I will definitely try a
larger accelerator pump jet per most of your recommendations. A big thanks
to all of your help.
"an off-idle flat spot ("bog") when the foot goes well down quickly." Is
exactly what is occurring.
I forgot to mention that it is a DCOE40 that I am using on my 1275. It was
a NOS (Made in Italy) one with Cannon manifold that I picked up through a
trade of a race Bugeye body many many moons ago. The fellow that I got it
from said that he had got it from a racer friend that had purchased it for a
race 948 engine. I guess that I figured that it might be in the ball park
of where it needs to be. I think that the Weber seems to be fine on the
upper end of the rev range once I let it "build" to the rev much more
gradually if that makes sense. The Weber also seemed to take well to
adjusting the idle jets. I think that is what they are called. You know .
. . when you set the screws at baseline and get the engine up to temp. and
then slowly back them out to get the rise in RPM.
I think that it will work well once I get the accel pump jet problem worked
out.
Thanks again to all you guys!
Mike C
----- Original Message -----
From "Robert E. Shlafer" <pilotrob at webtv.net>
To: "MICHAEL CARPENTER" <MAIL4CARPENTERS@peoplepc.com>;
<spridgets@autox.team.net>
Sent: Sunday, November 06, 2005 6:11 AM
Subject: Re: Weber DCOE tuning
Basically, what Rick Fisk said, Mike.
Is your Weber (kit) specifically set up (calibrated) for your motor?
Or, to put it another way....
is your motor in the same config. (state of
tune) as the carb. kit which is meant to serve it?
As otherwise, carb. calibration will normally require "tailering" and almost
always in
terms of the accelerator pump "shot" by
either quantity, quality or rate to avoid
an off-idle flat spot ("bog") when the foot goes well down quickly.
Another thing, in terms of sudden WOT,
variable choke SU's are very user friendly
when it comes to engines down a bit on
compression (vacuum). Fixed-choke carbs. like Webers are not, and most
especially so if the timing is a bit advanced.
Yet, another thing is most Spridget 948 or 1098 set-ups run 4.5 aux
venturis. 1275's can run the same but some kits feature a 3.5 size which
brings the main system in sooner, the difference being most apparent
upon sudden, WOT (or nearly so) acceleration below 2.5k rpm or so. The
difference can help "cover" for an accelerator pump "shot" that's not quite
"right" for the specific motor, in terms of
an off-idle "bog" or flat spot when the foot
goes down quickly.
Anyway....let's start with the kit. Is it "proper" for the motor to begin
with. For
back when there used to be two kits out
there. One for a tuned Mini-Cooper S and
another for the stock 1275 Spridget. The
former comes with (among other things)
38mm chokes, the latter with "34"'s.
Put the latter on a stock Series A 1275 and
it will "mimic" exactly the symptom you are
experiencing.
Cap'n Bob
Basic Frog
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