For U Solution

The four-barrel carburetor and corresponding four-barrel intake manifold allow increased fuel and air flow through the engine. You will commonly find four-barrel manifolds on large V8 engines that are intended for performance and power where the extra airflow can be turned into improved performance.

Four-barrel carburetors work by running the two primary barrels all of the time and only going into the secondary barrels when the driver signals the engine to provide additional power by pressing down hard on the accelerator. When the two secondary barrels open, more fuel and air flow through the intake manifolds and into the engine. Two-barrel carburetors do not have this option; theore they typically get better fuel economy than four-barrels due to the restricted fuel and air flow.

The increased air and fuel flow from a four-barrel carburetor, in addition to the two extra secondary barrels, create increased horsepower and acceleration when you drive the vehicle. The vehicle receives more fuel, which it can burn to provide additional power when driven. Vehicles with a four-barrel carburetor and intake manifold will accelerate more rapidly and efficiently than a vehicle with a two-barrel carburetor and intake.

An intake manifold is a primary part of the fuel-induction system and serves as the conduit between the carburetor and the ports in the cylinder head. Manifolds come in several types and designs. For instance, Edelbrock manufacturers and sells eight series of aluminum intake manifolds for various engine types. Ensuring that the airflow specs of the intake manifold match the requirements of the camshaft, cylinder and engine helps to guarantee peak performance, and making certain that the bolts on the intake manifold are tightened to the right torque specs helps create the necessary air pressure.

Torque is basically the amount of force applied to an object in order to twist or turn it. It is usually given in foot-pounds or inch-pounds, with one foot-pound equivalent to one pound of force applied to the end of a lever (such as a wrench) that is 1 foot long. Bolt torque specs for vehicle maintenance are often based on the bolts being clean or perhaps even lightly lubricated with clean motor oil. It is common to tighten the bolts on engine components in separate cycles. Tightening all the bolts to a given torque, and then returning to the first bolt and tightening each of them to a second, and then perhaps even a third, specification.

Here are some examples of bolt-torque specs for 1997 intake manifolds. These specs should not be applied to any intake manifolds other than the ones cited. For the intake manifold of the 1997 Ford Mustang 3.8-liter engine, first tighten each bolt to 96 inch-lbs of torque, then tighten each bolt to 15 ft-lbs and, finally, tighten each bolt to 24 ft-lbs. For the intake manifold on the 1997 Chevrolet Corvette 5.7-liter engine, tighten each bolt to 44 inch-lbs and then go back and tighten each bolt to 89 inch-lbs. For the 1997 Pontiac Firebird 5.7-liter engine, tighten each bolt to 44 inch-lbs and then go back and tighten each bolt to 7.5 ft-lbs.

There are two sets of numbers to be aware of: model number and the date of manufacture. Chevrolet manufactured aluminum and cast-iron manifolds, and number location differs on each. Both number sets on cast-iron manifolds are normally located near the carburetor mount. On aluminum models, only the model number appears in that location. Date codes on aluminum manifolds are stamped on the underside, making identification impossible without removal.

The model number code will be seven digits long. Youll have to check it against a list of Chevrolet manifold numbers, as there is no method to the numbering. GM, for General Motors, is usually stamped underneath. The date code will appear as a date, for example, 9.24.66.

Many Chevrolet manifolds are interchangeable depending on horsepower and other engine specifics. Identification by using casting numbers becomes important, as manifolds may have been replaced with ones from different engines over the years. People searching for manifolds at swap meets and junkyards should have casting number erence lists for positive identification.

Derived from the Latin root words for "many" and "fold," a manifold is essentially a chamber designed to distribute air to the cylinders. A manifold has two basic parts, the plenum (central chamber) and the runners (the passages that lead from the plenum to the individual cylinders). Air enters the plenum through a carburetor or throttle body, then the individual pistons suck that air into the cylinders as need be.

These terms refer to the manifolds intended application. A wet-flow manifold is one that carries both air and fuel, and a dry-flow manifold carries only air. Youll find wet-flow manifolds underpinning carbureted and throttle-body injected applications, which squirt fuel into the plenum. Multi-point fuel-injection systems typically use dry-flow manifolds, because they use fuel injectors to introduce fuel directly into the cylinder head instead of into the manifold. Dry-flow manifolds are generally more efficient, since engineers dont have to worry about the air and fuel separating around bends in the runners.

Generally speaking, a smaller plenum and longer, narrower runners will enhance low-rpm torque; large plenums and short, fat runners bias more toward top-end horsepower. This works in part because the small plenum and longer runners force air to speed up as it travels to the cylinders, which fills the cylinders more quickly. However, those longer runners will ultimately limit airflow, which hinders absolute, high-rpm horsepower potential.