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Weber 32/36 Setup, Ch.1

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Time to revisit some old-school tuning tricks!  The Weber 32/36 DGV (DGEV, DGAV, etc) downdraft carb was at one time a very common basic performance mod used by lots of people on lots of different carbureted compact cars and trucks.

Electronic fuel injection (EFI) is now the rule and carburetors the exception.  That leaves many people out in the cold when it comes to sorting out a downdraft Weber carb, but there are still a lot of people using DGVs on the old 2T-C, 3T-C, and 4A-C Corolla, Toyota 20R and 22R pickup and Celica, Datsun 510, and a handful of British sports cars like the MGB, Triumph Spitfire, etc.  With that in mind I thought it would be nice to revisit the topic and break down the setup and jetting procedure step-by-step.  By doing this, you can set up your carburetor to deliver the correct air-fuel ratio for your engine under the conditions in which you normally drive.

WARNING: Carburetor tuning involves disassembling a carburetor filled with gasoline.  This presents a serious risk of fire.  Have an appropriate fire extinguisher handy at all times!

For best results, you’ll want to follow this guide in the order in which it was written.  Often the success of any given step depends on the steps before it.

Before you begin to tune the carburetor, you must make sure that the engine itself is in good tune.  There is no point trying to tune a carburetor on a sick engine!  Make sure that the valves are adjusted properly and that the engine has good compression.  Set the base ignition timing correctly.  Be sure that the distributor’s mechanical advance mechanism works properly, that the vacuum advance canister works as it should and is connected to ported vacuum.  Verify that there are no vacuum leaks.  If the engine has problems, fix them before you play with the carburetor.  Don’t try to tune around other problems!

Be sure that the carburetor is clean inside and not excessively worn.  You need to be able to concentrate on setting the fuel mixture, not trying to work around other problems.  Set the float level correctly, and have a carburetor rebuild kit or gasket set ready.  Make sure you have no fuel leaks or other fire hazards.

All tuning should must be performed with the engine thoroughly warmed up to operating temperature.  This requires that the car’s thermostat and cooling system be in good condition.  You’ll also need to verify that the carburetor’s choke system is working and adjusted as designed.  That is not difficult, but is outside the scope of this article, as I am assuming you have done that before you begin tuning.

In tuning the DGV, you will be changing the idle jet, the main jets, and the air correctors (sometimes called air jets).  A carburetor jet is a small part with a precisely sized hole made to allow a specific amount of fuel or air through it.  Each jet is available is many different sizes to allow more or less fuel or air, thus allowing you to tune one basic carburetor to deliver the correct air-fuel mixture on a variety of different engines.  Jets are typically made of brass and have a number stamped into them representing their size.  Larger jets for the Weber DGV series have larger numbers; smaller jets have smaller numbers.  Main jets and air correctors have a slot for a flat-bladed screwdriver machined into the top.

The idle jet is accessible from outside the carburetor, located high on the right side of the carburetor body, under a screw near the top of the float bowl.  Some DGV-series carburetors use an electric solenoid to cut off the flow of fuel to the idle jet when the ignition is turned off, and this small solenoid is located directly over the idle jet.  Unscrew the solenoid or screw to access the idle jet.

The main jets are located at the bottom of the float bowl, close to the venturis, toward the rear.  The air correctors sit at the top of carburetor body, behind the float bowl.  Both of these are located under the the float bowl lid, which covers the top of the entire carburetor body.  Removing and replacing the float bowl lid is a bit of a hassle, but you will have to take the float bowl lid off to access the main jets and air correctors.  In the course of tuning the carburetor the float bowl lid may have to be removed and reinstalled many times.  Try not to lose the clip holding the choke arm to its linkage, but in case you lose it, you can get a pack of c-clips at a hobby shop that sells radio control models.

One final note: patience and attention to detail can produce a pretty good street setup, but to get it really right, a wideband oxygen sensor and gauge are really invaluable.  If you use one, bring an assistant along to read the gauge and take notes as you drive.  Make sure you calibrate the gauge correctly before use, or it may give inaccurate readings, which are worse than no readings at all.

Time to move on to Chapter Two and start tuning!

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