John, Dick, List,
This situation was actually described in Nelson's famous ZS articles on the
Buckeyetriumphs site. In some applications the ZS's will lean out under certain
conditions, due to the damper rising too fast.
The dampersprings will not be part of the problem as they just set the damper
height under a certain vacuum amount in the inlet manifold. It is the damper
function that decides how fast the dampers rise if a (sudden) vacuum is
created, by flooring for instance.
The damper function can be strengthed in 2 ways:
1. Thicker oil wil work up to a certain amount;
2. By limiting the opening in the damper where the oil flows through, inside
the the small damper tube of the carb, same effect can be obtained.
To create the 2nd situation, one can place a small washer next to the little
cylinder on the damper screw of the carb, or one can make a slightly longer
cylinder. The damper will be forced to rise slower, keeping the mixture richer
under sudden acceleration conditions.
I know of one car in my area where this solution has been implemented with good
succes. I think it is in the 4th article (tuning the zs carburettor) on the
This should work in a similar way on SU carbs as well I would think?
(lurker in the NL)
> On Tue, Jun 1, 2010 at 2:37 AM, Sally or Dick Taylor
> <firstname.lastname@example.org> wrote:
> > John---Does the A/F monitor show full rich only at idle speeds? If so, does
> the monitor then recover into the rich area after rpm picks up? I need this
> info to give more help! Meanwhile, I'll just guess as to the problem and
> possible solutions.
> > a) The air valves are flying open because the oil in the dashpots is too
> > b) The springs that help to keep the airvalve from coming up too fast are
> either missing or weak.
> > c) One carburetor is running too lean, but the monitor is sensing richness
> because the other one is too rich. (Measure the diameter of the needles right
> where they exit the air valves. They should be identical.
> > d) While the needles may be too rich at idle, they are not thin enough just
> off idle. (Your monitor is showing you the lean condition)
> > e) Be sure the ign. timing is advancing and following the engine speed.
> > There could be other problems, but making this list longer won't "get it
> > Dick