I ran into a similar problem when installing my triple
stromberg setup a few weeks ago. When I revved the
engine, the revs would drop very, very slowly. I
traced this problem to the air bypass valves on the
carbs. These valves are used to create this condition
(although probably not so exaggerated) on purpose for
emissions reasons. If the revs are allowed to drop
very quickly, it apparently creates a condition that
the emissions legislators don't like. You can read up
on these bypass valves in the fantastic Haynes manual
on Stromberg carbs. Basically, these bypass valves
allow air to bypass the throttle (butterfly) when a
very high amount of manifold pressure exists (as when
the engine is decelarating under no throttle, called
engine braking). This allows air to get to the engine
and keeps the revs from dropping too quickly. What I
did was remove the bypass valves and place a thin
piece of cardboard (about the thickness of a gasket)
between the bypass valve body and the carb body,
blocking off the air passages. These effectively
bypassed the bypass valves, and now the engine drops
back to idle very quickly.
You shouldn't have to do this on a regular spec 6, but
perhaps in fiddling with the vacuum pipes, you have
now created a condition which opens the air bypass
valves. Try bypassing these as I have described, and
maybe that'll fix your problem.
Tim Holbrook
1971 TR6 (with throttle linkage problems being fixed
on the recently installed triple stromberg setup)
> Date: Mon, 15 May 2000 14:16:42 EDT
> From: RedTriumphTr6@aol.com
> Subject: 74 EGR valve removal/replacement
>
> Fellow 6packers: My 74 1/2 seems to have a vacuum
> problem that plagues me
> periodically. I found my idle refusing to drop
> between shifts ...seems to
> stay at about 2200, but then creep back down to 800
> if I wait about five
> seconds at stop, as at an intersection. I pulled
> off the tube to the
> vacuum
> retard at the distributor and to my dismay found
> only a 150 to 200 rpm
> increase. Before the problem the rpms jumped up
> about 500 (to 1300) until
> the tube was reconnected. My troubles seemed to
> start after I cleaned and
> hosed down the engine this weekend. I had a similar
> problem last month,
> but
> it disappeared and the vacuum was maintained after I
> removed and cleaned
> all
> of the emissions tubing. Could I have plugged up
> something with water or
> gunk when I cleaned the engine? I am again going to
> take all the tubes off
> and clean them, but I do have vacuum to and from the
> carbs...the problem
> area
> seems to be no vacuum from the distributor to the
> several tubes on the
> thermostatic switch on the radiator hose and to and
> from fuel traps. Could
> the thermostatic switch be bad or the vacuum retard
> unit need replacement?
> If the latter needs to be replaced, how is it
> removed from the distributor?
> I don't see a nut or screw to loosen; the long end
> of it just seems to be
> inserted into the distributor somehow. Bentley's
> manual does not seem to
> explain how to remove it.
> Also, another concern may be relevant here. I
> thought that I would
> remove the EGR valve and inspect it, but I may have
> screwed up..I thought
> that the screw on top of the valve was to be turned
> for removal of the
> valve.
> I found it very difficult to turn, applied some
> rust penetrant, and
> finally
> it would turn somewhat. I then saw that the valve
> unscrews from the
> manifold
> (I think), and this small screw may not have
> anything to do with removal.
> What does it do...some internal adjustment or does
> it help dismantle the
> valve itself for cleaning? Did my tinkering with
> this somehow break
> something
> inside the valve, causing my current vacuum problem?
> I hope I do not need
> a
> new valve, as no supplier seems to sell one ....help
> guys? (I noted the
> problem after cleaning the engine and then messing
> with the valve...started
> car only after doing both. I then noticed the
> vacuum problem.) One final
> thought..... I have slightly adjusted the by-pass
> valves on both carbs by
> turning the screw a half turn or so w/o any affect
> on my idle, as the
> vacuum
> problem does not allow for any idle change....can't
> follow the Moss
> catalog's
> instructions as a result to reseat the valves.
> Thoughts guys on any of
> the
> above? Bob Pierson
>
> CF29461UO
>
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>
>
>
>
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