There are two basic styles of Weber's. There are Progressive Webers and Synchronous Webers. They
are all two barrel mechanical carbs. The progressive will open up the first barrel half way then
the second one kicks in. The 32/36 and 34/34 are both progressive. The video below shows the
The synchronous carbs have barrels that open equally at all times. The 38/38 and 36/36 are this
action. The video below shows that.
This is generally the deciding factor when purchasing the kit. For normal everyday drive the
Progressive carbs tend to work well. They get better gas mileage and do not have load up (flooding)
issues. The Synchronous carbs are better for performance. Headers, hotter ignition, even a cam
help soak up this larger carburetor. Determine the motor condition you are going to put it on.
Most Webers are going to be a performance upgrade compared to the 20-40 year old carb they are
replacing. Determine how the motor runs. Inline 6's don't turn the RPM's that a four cylinder
will. Heavy flywheels, cast iron heads, low revving motors can be just fine with a progressive carb
whereas a synchronous may overload because you have the ability to go from idle to FULL throttle
Fuel pressure is another consideration. Generally, if it is a mechanical fuel pump it is in the 2
to 5 psi to keep the Weber happy. Electric fuel pumps will over power the needle and seat, the
pressure is higher than the spring rate holding it back. Blowing past the needle and seat leads to
flooding. A bouncing float does the same. People occasionally complain about the Webers flooding
on extreme hills while off-roading. This can be due to the brass float bouncing. You can replace
it with the much lighter plastic float and alleviate many of the problems.
The choke is another area of interest. Most of the Webers come in to the US with a water choke.
Then they are converted to electric. You can even get a kit to convert them to manual choke. This
explains the lettering series you often see. For example you may see a 38 DGAS, the third digit
stands for the choke, in this case Aqua, a 38 DGES would be an electric choke. They are the same
carb, just different chokes. Most Webers sold in America are electric choke with ones going on
Suzuki Samurais being the exception, they are generally water choke. The choke is a thermal
electric which needs to go to an IGNITION HOT 12 volt source. Do not hook it to a constant 12 volt.
This voltage along with the engine temperature causes the coil to expand or contract and open or
close the choke flaps. Sometimes the chokes may need to be set. This is easy, the electric has a 3
screw bezel. Loosen the bezel and the round body will twist like a watch dial. Generally, going
through 2 heat cycles of your engine and you can get it set accurately.
Weber Carb Kit
Kits come with 4 parts, the manifold adapter, linkage adapter, carburetor, and washable air filter.
This allows the kit to be bolted to your factory intake manifold. The linkage for the most part
is cable, on some kits, we will specify rod linkage. None of the kits allow for a kickdown on an
automatic transmission. All carbs are the same size and shape, the difference is the adapters.
This means that other than jetting there is no difference in the Weber that goes on your Toyota or
Jeep or Suzuki or VW. Weber carbs kit are not smog legal or pollution controlled.
Vacuum and Smog
Webers are a stand alone carburetor. This mean that you are not going to need anything from your
engine for feedback. This mean that all of the emission, EGR, and many of the vacuum lines can be
done away with. Most only need 3 things for vacuum. The distributor advance, PCV valve, and the
brake booster. So the rest can be blocked. Webers have not received a CARB number and are not
considered to be smog legal. Check your local laws concerning the use of a non stock
For reference, look at the labeled picture, this is how we refer to the parts of the carb:
A - Choke butterflies
B - Secondary barrel
C - Primary barrel
D - Idle speed screw
E - Air mixture screw
F - Vacuum
G - Accelerator pump