Manifold drain tube question

[tommyintpa@aol.com]

<font FACE="arial,helvetica"><font SIZE="3" FAMILY="SERIF" FACE="Calisto MT" LANG="0">Can anyone explain how the intake manifold drain-tube (or as I see it also
referred to as the boil over tube), doesn't destroy the manifold vacuum? Can
anyone shed some light on this?

Gary Schulz



Hi, I purchased one from Hugh, when I received it boy was I surprised. This
thing is two feet long bent like the trap under the sink. I installed mine
with the 180 degree bend at the bottom but I think that the vacuum would be
so great that it would suck the fuel in the pipe back into the manifold even
if it were full to the top. Maybe one of the "motor guys" can explain this.
Do other cars with this type motor have boil over tubes? Tommy in Tampa</font>

 

[Gary Schulz]

Can anyone explain how the intake manifold drain-tube (or as I see it also
referred to as the boil over tube), doesn't destroy the manifold vacuum?
How does the vacuum advance work when the manifold drain tube appears to be
open to the atmosphere? What am I missing? Is there supposed to be an "S"
bend in it so that once it collects enough fuel it seals like a trap in a
drain? Can anyone shed some light on this?

Gary Schulz

 

[Schulz Gary-FGS111]

<table>
<span class="410332214-01052001"><font face="Arial" color="#0000ff" size="2">Does anyone else have a 180 degree bend in their boil over tube? The books all seem to show pictures of straight tubes. I'm still at a loss to explain how this doesn't destroy the manifold vacuum. I'd like to have a poll on straight vs. bent.</font></span>
<span class="410332214-01052001"><font face="Arial" color="#0000ff" size="2"></font></span>
<span class="410332214-01052001"><font face="Arial" color="#0000ff" size="2">Gary Schulz</font></span>
<blockquote>
<div class="OutlookMessageHeader" dir="ltr" align="left"><font face="Tahoma" size="2">-----Original Message-----
From: tommyintpa@aol.com [mailto:tommyintpa@aol.com]
Sent: Sunday, April 29, 2001 11:18 AM
To: amphicar-lovers@yahoogroups.com
Subject: Re: [amphicar-lovers] Manifold drain tube question

</font><font face="arial,helvetica"><font lang="0" face="Calisto MT" size="3" FAMILY="SERIF">Can anyone explain how the intake manifold drain-tube (or as I see it also
referred to as the boil over tube), doesn't destroy the manifold vacuum? Can
anyone shed some light on this?
Gary Schulz

Hi, I purchased one from Hugh, when I received it boy was I surprised. This
thing is two feet long bent like the trap under the sink. I installed mine
with the 180 degree bend at the bottom but I think that the vacuum would be
so great that it would suck the fuel in the pipe back into the manifold even
if it were full to the top. Maybe one of the "motor guys" can explain this.
Do other cars with this type motor have boil over tubes? Tommy in Tampa</font>

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</blockquote></font>

 

[David Chapman]

The inlet manifold design of the Triumph engine fitted with the Zenith/Solex
carb is such that if there was a leak in the float chamber or somewhere else
in the carb then, without the tube and with the engine stopped, fuel would
drain into the
engine and cause onehelluvabang when it was started.

All Triumph engines with this carb/manifold layout had the tube, it allows
fuel to drain
safely (!) into the Amphicar bilges.

Mostly the tube is dry but parked on a hot day with a hot engine some fuel
can get past
the needle valve in the carb, mostly not enough to fill the U bend.

Re the vacuum leak, yes there will be a bit but negligable, very little air
could leak in through
that tube.


David Chapman



>Can anyone explain how the intake manifold drain-tube (or as I see it also
>referred to as the boil over tube), doesn't destroy the manifold vacuum?

 

[tommyintpa@aol.com]

<font FACE="arial,helvetica"><font SIZE="2">In a message dated 5/2/01 12:45:48 AM Eastern Daylight Time,
fgs111@motorola.com writes:





</font><font COLOR="#0000ff" SIZE="2" FAMILY="SANSSERIF" FACE="Arial" LANG="0"><blockquote TYPE="CITE" style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Does anyone else have a 180 degree bend in their boil over tube? The books
all seem to show pictures of straight tubes. I'm still at a loss to
explain how this doesn't destroy the manifold vacuum. I'd like to have a
poll on straight vs. bent.</font><font COLOR="#000000" SIZE="2" FAMILY="SANSSERIF" FACE="Arial" LANG="0">


</font><font COLOR="#0000ff" SIZE="2" FAMILY="SANSSERIF" FACE="Arial" LANG="0">Gary Schulz</font><font COLOR="#000000" SIZE="2" FAMILY="SANSSERIF" FACE="Arial" LANG="0">

</blockquote>



Hi again, The two boil over tubes from Hugh are about 2' long with that 180
degree bend about 6" wide. Undoubtedly the illustrations that I see in the
catalog are from nonamphi motors. This pipe is very long in relation to its
diameter, that probably translates to the resistance to air flow that is
necessary to maintain manifold vacuum.
The thing is, there are a lot of cars running today with that pipe broken off
at the manifold. Both my cars arrived that way. Look at the manifold below
the carburetor on the drivers side, you will see a nut it is really a brass
ferrule nut. If a small brass pipe is not extending from that nut you have a
hole in the side of your intake manifold that is sucking in UNFILTERED AIR at
the same time lowering manifold vacuum for sure. Tommy in Tampa</font>