Frank:
Matt hit most of the bases. The 42DCOE can be made to work well on
your car. A stock MG engine needs to have pretty small chokes as Matt
pointed out to keep flow speed high, otherwise the fuel won't get to all
four cylinders effectively.
For the same reason (siamese ports) you want a pretty big pump jet.
To quote one Weber authority, "squirt enough in, so that it can sort itself
out".
Hopefully you have a long manifold. There is a short manifold that
does not work very well at low revs.
On a stock engine, to be drivable a DCOE with small chokes will
probably not flow as much as a stock 1 1/2 SU setup at high revs. As a
simple bullet proof carb, the DCOE is great for street use. But matching
high rev flow with low speed drivability is not going to happen.
The distributor on your 71 MGB is designed to function with "ported"
vacuum. This is taken off right at the carb butterfly. The DCOE does not
have this port. Your best bet would be to have the distributor recurved to
run as centrifugal only. At highway speeds you will be losing a bit of
mileage, but response will be improved through the rev range.
The cold running assembly is handed. In usual form the cable
linkage points in the wrong direction for the MGB (carb on left)
application. Weber does sell the opposite handed assembly, but it ain't
cheap. One way to deal with it is to run a long cable under the carb and in
from the front. The cold running assembly has a built in spring that should
be strong enough to pull off on it's own. If not the gears may be sticky,
or the slides gooed up internally. Both easy to fix.
I like the DCOE carb. They are very simple to work on and tune.
When set up correctly they are very drivable. But when choked to work well
at low speed they may not give as much power on the top end as a pair of
SUs.
HS4 SUs are more tricky to set up correctly and are prone to wear.
But will give a better overall performance than a single DCOE.
Kelvin.
-----Original Message-----
From: Frank Krajewski [mailto:frankk@intap.net]
Sent: Friday, March 10, 2000 7:53 AM
To: mglist
Subject: Weber Woes
I picked up a 1971 MGB recently on which the PO had installed a side
draft Weber 42DCOE8, Number 4E. He couldn't get it to run smoothly and
neither can I! Seems he, nor I, can find a place to connect the vacuum
advance line on the manifold or carb. The vacuum line from the
distributor is there but disconnected. Does anyone have any insights?
Also cannot determine how to connect the choke cable. The PO has it
connected but it is not connected properly and the choke engages but
will not disengage unless I pop the hood/bonnet and restore it to its
original position by hand! I suspect this is not the proper Weber for
this car and may not even have a vacuum advance connection.
Frank "Swamp Yankee" Krajewski
http://www.bmcne.com
|