Daniel: Thanks for the beginings. I have a Weber book by Pat Braden and one by
Des Hammill. Both are interesting, but actually not that helpful because: 1. I
don't have a dyno and 2. It seems that jetting is mostly a trial and error
affair that involves 15-20 bucks a pop (8-12 British Pounds Sterling, I think).
I had all the venturi/jet info written down somewhere...now will have to take
carb apart again to regain that info. I'll send it to you when I do that.
Meejit's down while I wait for a water pump and alternator anyway. Thanks
again.
Geoff Branch '74 Meejit
----- Original Message -----
From <Daniel1312 at aol.com>
To: <branch@valinet.com>; <spridgets@autox.team.net>
Sent: Saturday, April 01, 2000 3:13 PM
Subject: Re: Weber DCOE 45
> Geoff,
>
> I assume you mean the jet inspection cover was missing when you refer to the
> Micky Mouse hat.
>
> You need a short lesson in how the DCOE works.
>
> The engine via the DCOE draws air into the inlet manifold and induction tract
> in two distinct places. The first is round hole about the size of a dime
> that is on side of the carb (left hand as you look at the carb) above the l/h
> barrel (a good book or photo might help). This hole is used to draw are into
> the carb body, more of which later.
>
> The engine gets the rest of its air through the carb barrels.
>
> If the carb is correctly calibrated (like on a chassis dyno) and the jet
> inspection cover comes loose or is missing (lost) the engine will run rough,
> particularly so in mid range rpm (long time since that happened to me but I
> think it is the 2,500 to 3,800 rpm range). At higher rpm there does not seem
> to be a problem.
>
> Back to the dime size hole. If you remove the carb top cover complete you
> will see that the hole leads up to the top cover resticted by the top cover
> gasket such that it gets to the area underneath the jet inspection cover.
> This air is drawn into the gallaries that feed the emulsion tubes with air.
> It is this air that is mixed with fuel drawn up in the jet (idle or main
> depending on rpm) that is subsequently drawn into the air flow from the
> barrels that is subsequently further emulsified.
>
> If the jet inspection cover is missing then air is either drawn into the
> emulsion tubes/holes in greater quantity than would be the case when air is
> drawn in only by the dime sized holes OR... air is drawn in a lesser quantity
> by virtue of a weaker vacuum. To be honest I don't know which it is.
>
> BUT
>
> Either the mixture leaving the jets (via the progression holes or aux venturi
> is richer or it is weaker.
>
> SO
>
> Obviously your car is not correctly calibrated at some point in the rpm range
> but I cannot say whether it is too rich, weak or just poorly emulsified.
>
> However, if you provided a spec of the engine along with FULL details of the
> calibration of the carb I ought to be able to guess and along the way add to
> my knowledge of how the carb works (eg missing jet inspection cover leans/ or
> richens mixture to detriment).
>
> Finally, the jet inspection cover is there for a purpose (eg unfiltered air
> enters directly into the jet system without it) so buy a new one
> (aptfast.com) and then get the jetting sorted.
>
>
> Daniel1312
>
> PS. Most books on the DCOE aren't that good but you might find it helpful to
> buy some anyway.
>
> In a message dated 01/04/00 18:01:26 GMT Daylight Time, branch@valinet.com
> writes:
>
>
> << And on another note: My 1275 had been suffering from a hesitation/misfire
> at
> low rpm and high load situations. Then it went away. Runs Great! So I went
> a-looking for a reason and found the mickey-mouse hat on the Weber was
> missing!!!!! For anyone with Weber side draft experience then:
> 1. Why would this improve the performance of this carb?? And what does it
> indicate is wrong with it with the hat on?
> 2. Should I just leave the damn thing off?
> >>
>
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