Dear reader : The following is an extract from the Magazine :

Street Rodder

Edition April 1999

Extract from the feature

"Getting Drafted"

based on a visit to :

INGLESE INDUCTION

SYSTEMS, LTD.

406 S. Orchard St., Dept. SRM

Wllingford, CT 06492

(203) 265-3617

E-Mail: llSystems@aol.com

By Jim Rizzo

No pictures have been included in this extract, and it is strongly recommended that you do aquire the original magazine to take full advantage also of the pictures and the specifications therein included, to the credit of the research work done by the author.

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You've got to admit there's no other carburetion system on the planet that looks as exotic, or is as visually stimulating, as a quartet of dual-throat Weber carbs. Be they sitting atop a big-

block or a cement block, their forests of highly polished velocity stacks elicit sensations of both brutal power and exceeding mystery. But now, thanks to Mickey Lauria of Inglese Induction Systems in Wallingford Connecticut, the mystery part is about to be all but erased.

Since 1981, Inglese Induction Systems has become the most influential and established Weber carburetion experts for V-8 engines in America. The company's early involvement (during the '70s) revolved around working with Shelby-American on Weber carburetion for Shelby Cobras.

This relationship led to national involvement with more and more Cobra owners which, in turn, caught the attention of those looking for parts, tuning, and technical support for more exotic Fords like GT-40s, and Daytona coupes.

By 1980, Inglese began to research and develop its own designs for Weber systems for Chevrolet V-8s (and a short time later Buick V-6s). Then, in 1981-82, the company began designing and casting its own intake manifolds and system components for use with Weber carburetors. This gave them much greater control in terms of design features and quality control. Since then, Inglese Induction Systems has designed and built well over a thousand complete systems which have seen action on everything from race cars to street rods-and just about everything in between!

TIE WEBER MYSTIQUE

Since its invention in 1925 by Edoardo Weber in Bologna, Italy, Weber dual-throat carburetors have graced some of the most exotic production and race car engines in the world. And since that time, no other carburetor has been as dosdy associated with high-performance as the dual-throat Weber. Along with this association came much fame and recognition by legions of performance enthusiasts, but alas, myth and misinformation have unfortunately become part of the Weber mystique, as well.

The most prominent bits of misinformation that seem to be spread among the ranks of the uninformed are that Webers are extremely hard to tune, virtu ally impossible to synchronize,

and their workings totally incomprehensible.

Nothing is farther from the truth, and with a bit of information and education provided by Mickey Lauria and Inglese Induction Systems, we'll do our best to dispel the mysteries of Weber carburetion.

WEBER MODELS AND IDENTIFICATION

Perhaps the best place to begin is to leam a bit about the different types and model designations of the most popular carburetors. Weber produces two carb designs: the side-draft and the downdraft.

The sidedraft (as the name implies) was designed to be mounted horizontally with its venturi parallel with the ground, which makes it the perfect design for use on in-line engines or on V-8s where hood clearance is minimal. The downdraft (again, as the name implies) was designed to be mounted upright with its venturi perpendicular to the ground, and seems to be the more popular choice among street rodders.

Now, the model numbers and designations used on Weber carburetors can be most perplexing to the uninitiated. This is due mainly to the fact that Mr. Weber initially began building carburetors for specific uses. Thus, he never gave thought to a practical series of identification designations. He also used his native Italian in naming the designs, which, if you're not familiar with words like doppio (double), corpo (throat), or orizzontale (horizontal), definitely adds to the confussion. So, let's see if we can help you get a handle on all of this!

Webers are designated with a series of numbers and letters. To illustrate this we'll use the Model 45 DCOE-21 as an example:

The first set of numbers (called the prefix) always denote throttle plate diameter,

Letters following the prefix refer (usually in Italian, mind you) to the general type of carburetor,

and the last number or numbers (called the suffix) refer to variations of basic carburetor type.

(We'd like to note that for the most part, suffix or variation numbers will rarely come into play when outfitting your street rod, as we're assuming you'll procure your Webers from an authorized dealer, not an Italian bone yard.)

As we previously stated, the "D" stands for double, the "C" stands for throat, and the "0" stands for horizontal. We can't honestly say what exact word the "E" stands for, but we can assure you that from what we understand, it denotes a die-cast carburetor body. This makes our example a 45mm doppio corpo orizzontale, which, when translated into gear-head, means it's a die-cast 45mm dual-throat sidedraft.

Somewhere along the line, you may recall seeing a set of 48 IDA's on big-block Chevy You've also more than likely seen that same 48 IDA setup on a small-block Ford, for instance. And, you may have questioned how that same carburetor setup could work on two vastly different engines. It would seem that one of'em would have to be either seriously over- or under-carbureted. Well, actually, this isn't true, because they really arcdt the same carburetors at all! The only things these two sets of carbs have in common are their outward appearance. This leads us to the most interesting characteristic of the Weber design-the interchangeable "choke" or venturi. This feature allows a Weber to be instantly converted from a large-cfm carb to one of a smaller cfm, or vice-versa.

By installing a smaller venturi, the carb is constricted, and will thus flow less cfm, which helps with mid-range performance or makes it more suitable for use on a low-compression small-block engine. Conversely, pull out small venturis and drop in larger diameter ones, and you've got a set of Webers that'll flow enough cfm to make a big-block scream!

In order to get driveability, good throttle response, and lots of torque from a Weber carbureted engine, venturi size is the first consideration. Once the correct venturi size has been selected for the application, the jetting for the rest of the circuits is established around that venturi size.

THREE CIRCUITS

For the sake of simplicity; let's look at the Weber as having three basic circuits:

The idle circuit

The accelerator pump circuit

The main circuit

The idle circuit is comprised of two components: the idle jet and the idle jet carrier. These two components allow the tuner to select the exact fuel/air mixture provided to the engine at idle and low rpm operation.

The idle mixture is delivered as a proportioned mixture whose total volume can be further regulated with the idle-mixture screw, located on the lower part of each carb barrel. On a correctly jetted idle circuit, the mixture screw on a 48 IDA is never more than a 3/4 turn out! If you have to go any more than that, you'd better heavy-up the idle jet because going more than a 3/4 turn to get an idle indicates a lean jet that's going to contribute to other driveability problems.

The Weber idle circuit isn't just an idle circuit-it does more than that. It's actually the circuit that carries the engine all the way up to 2,800 to 3,000 rpm, when the main circuit finally takes over. So, if you have a tuning problem that goes away after about 3,000 rpm, the idle circuit would be the place to start troubleshooting.

One of the most frequently encountered "gremlins" with Webers is an annoying "flat spot" at about 2,200 to 2,800 rpm. This condition is caused by one of two things: either an incorrect emulsion tube (which will cause a rich stumble due to an under-emulsified mixture), or the idle circuit is falling off before the main circuit can take over. (Seeking some sound advice from the professionals at Inglese can be a big help in situations such as these.)

The accelerator-pump circuit is responsible for eliminating "bog" or making a passing maneuver without hesitation or stumble. The circuit has two basic elements: the pump exhaust valve, and the pump jet.

The pump exhaust is nothing more than a bypass valve (located in the bottom of the float bowl). Its job is to regulate how much fuel is made available through the pump jet when you mash on the pedal. The duration of the pump shot is controlled by the size of the jet; a larger pump jet gives a heavy blast over a short period, while a smaller one will give a finer, longer duration shot.

The main circuit is where the power is made. It has three primary elements: the main jet, the emulsion tube, and the air corrector. The main jet is stuck into the bottom of the emulsion tube (submerged in fuel). As the carb begins to work, the main jet meters the amount of fuel allowed to pass up into the "main-well" around the emulsion tube. Air enters the top of the emulsion tube through the air corrector (which meters the amount of air to be mixed with fuel), and out through a series of holes along the tubes length (aerating the fuel rising up around the tube). This "emulsified" mixture is then sucked out of the main delivery nozzle (around 3,000 rpm, or so) and you're down the road like a shot.

Tuning the main circuit for maximum power is something that can be achieved by a few test runs and a handful of jets.

The basic rules with Webers are: to change the entire rpm range, play with the main jet; if you want to change the high-end, play with the air corrector. You should note that the air corrector is a much finer adjustment than the main jet. For instance, one step up in jet size (richer) equals about three steps down on the air corrector (less air = richer mixture). An air corrector change would be appropriate, for instance, if the engine pulls strong up to 5,000 rpm and then goes flat. This would indicate a lean condition up top; drop the air corrector three sizes or so, and you should be able to run the engine up to around 7,000 rpm. If the engine feels sour all the way up, go one or two sizes up on the main jets only.

People don't realize that the Weber carburetor is an extremely simple design with very few moving parts. There are no metering rods, power valves, rubber seals, or plastic parts. The accelerator pump on the 48 IDA is a brass piston, the throttle shaft rides on precision roller bearings, and the floats are brass units which will not become fuel-logged with age-they're superior examples of precision machining and are very unlikely to fail, leaving you stranded someplace.

This is another reason the Weber is well suited to street rod use and long distance cruising. If you know someone who's suffering driveability problems with a Weber system, he's doing so unnecessarily. With knowledgeable folks like Mickey Lauria and his crew at Inglese Induction Systems, no nonsense information and proper tuning tips are but a phone call away. Don't let misinformation and myth keep you from sporting the most impressive induction system there is on any street rod!