METERING
NOZZLE & CARBURETOR TYPES
(also
known as customer response #32..."What do you mean 90
degree, 180 degree?")
The
1600 38mm (1 1/2") and the 2000 46mm (1 3/4") carburetors
each come in two styles. One is designed for "90 degree
nozzles" the other is designed for "180 degree nozzles".
Whether or not the two types still have the nozzle type that
they left the factory with is anybody's guess. Mechanics,
car owners and parts counter people don't always know the
differences, and the murky "official" parts book doesn't
help much. Originally the 65-67 1600 and the 67 and some 68
2000's came with the 90 degree nozzles. A lot of cars have
been altered.
The
term "90 degree" or "180 degree" refers to the relationship
between the fuel pipe fitting on the nozzle, and the
threaded hole for the linkage screw. If you turn your nozzle
upside down you can see that they are either directly across
from each other (180) or at a right angle to each other
(90). You can also just look at these pictures. The correct
float bowl for the 90 degree nozzle has a fuel outlet that
points horizontally at the throttle body portion of the
carburetor. The 180 degree type float bowl has a fuel outlet
that points downward at a 45 degree angle, towards the air
cleaner. (Your float bowl may or may not have the drain
plugs shown on the bowls above.)
The
biggest problem with the SU carbs on the roadster isn't the
carbs themselves, it's what has been done to them since they
left the factory. Parts from both types are mixed together
and the result is something that either doesn't work right,
is prone to fire, or both.
The
metering nozzle, the black plastic part you see go up and
down when you pull your choke, has to be able to go up and
down smoothly, and return completely with no drag. When you
lift the piston inside the carb up just a tiny bit and let
go, it should drop down with a noticeable click or thump. It
should sound the same with the choke cable pulled or not
pulled. If you pull the choke cable, then push it in, you
shouldn't be able to touch the nozzle with your finger and
have it pop up the rest of the way, it should already be up.
If
the wrong nozzle is used for the particular carburetor, the
linkage piece that moves it will not match and can lead to
binding. If the fuel pipe has been replaced with the wrong
one, or by one out of some other material, this can also
lead to binding or worse, fire. This small tube, is
manufactured from extremely high quality heat resistant
neoprene, which is not normal fuel line. It is also moulded
so that it has NO STRESS on it when it is installed.
Granted, the original moulded ones are relatively expensive,
if you don't figure in the costs of a possible fire. If you
are attempting to use a substitute type of line it has to be
out of a material that has a HIGH resistance to hardening
from the heat, and a HIGH resistance to cracking from
motion. If I had a nickel for everytime someone brought a
car to me after it had been "professionally" tuned up only
to find it was running horribly because the choke stuck the
next time it was used due to stiff fuel pipes...
A
sticking nozzle can also be caused by a bent needle or a
metering nozzle that is not centered. (That's a whole other
subject!)
If
it was safe and workable to use 30 cents worth of vacuum
line, Nissan would have done it. It isn't, and they didn't.
When you get a fuel leak it goes right on the exhaust
manifold. I hate repairing burned roadsters, and I hate
having to buy one that can't be repaired.
Fire
can also be a possibility due to improper length (or
missing) fuel overflow tubes. Basically you want your fuel
overflows that connect to the top of the float bowls to run
down below the exhaust manifold. You can use the original
long metal tubes or use the shorties with a piece of fuel
line attached and routed down away from the
exhaust.
What
we wanted to do with this page is at least show you what
float bowl goes with what fuel pipe and nozzle type. From
this you can determine if your car is a hodgepodge of
mismatched parts.
2000
90 Degree Nozzle Parts Situation...
The
90 degree nozzles for the 2000 come in a "front carb" and a
"rear carb" version. The 1600 90 degree nozzles are the same
front and back. One of the 2000 90 degree nozzles is getting
extremely difficult to find. Usually you have to buy two of
the one that is available and have someone very careful and
patient unpin the brass shaft and reuse your old lower
plastic part. If this is the case the kit description will
say "To Modify Nozzles". If we have the F and R nozzles the
kit description will say so.
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