Eric, Henry, correct.... Charles just slightly reversed...could be
terminology only.
More air in means more fuel required to keep the proper F/A ratio.
You usually need stiffer dashpot springs with free flow filters
to keep the mixture richer while accelerating.
By dropping the in/Hg pressure in the air box (more restrictive filters)
the vacuum the engine pulls on the throats of the carbs will pull
more gas out of the jet. It's the air velocity through the carb throat
that creates the vacuum in the dashpot chamber making it rise.
Reducing the restriction... (free flows... ) the vacuum created by
the engine does not act on the gas the same way...hence the
need for stiffer dashpot springs to keep the pot from rising
before the gas is actually drawn up past the needle.
Less restrictive breathing means the increase in air speed will
create a greater vacuum in the dashpot quicker, as it rushes past
the holes in the bottom of the dashpot, thus making it want to sooner.
The speed in which it will lift...it strictly the dash pot oil.
Simple test to analyze this for yourself.....
Just unscrew the dashpot piston and watch how quickly the pots
will rise when you pull on the throttle cable.
You'll possibly even be able to have the engine die as the A/F
ratio will drop abruptly enough to starve the engine of fuel.
Now do the same thing but with a paper towel carboard tube stuffed
in the carb like a super long ram pipe. The air speed will take
slightly longer to accelerate down the long ram pipe. This increase
in vacuum will pull more gas before the piston starts to rise
and will not 'choke' the engine as abruptly.
Paul Tegler ptegler@gouldfo.com www.teglerizer.com
----- Original Message -----
From: "Henry D. Reynolds" <hdr@jump.net>
To: <mgs@autox.team.net>
Sent: Thursday, February 28, 2002 10:51 AM
Subject: Re: MGB Improvements
The first mod i would make would be a Maniflow header.
this statement contradicts everything i (think) know about
carburetion: "(a) free flow filter doesn't 'restrict' enough to create
the proper vacuum needed for the carbs. to work just right."
how can this be true? would anyone care to explain (on or off list).
Changing air filters will require you lean out the mixture or,
possibly, replace the dashpot spring to prevent the venture from
completely opening before the throttle.
--
Henry D. Reynolds - System Admin
mail: hdr@jump.net - phone: 512.448.3617 - cell: 512.699.8658
Key fingerprint = 3F 5A FD F6 E5 40 55 9C 7F 0F 81 F5 0A E6 3B 7F
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