October 1, 2006

It's Not uncommon for old-school auto enthusiasts to switch from fuel injection to carburetors. To many, carburetors are simple and practical in terms of installation and use. Carburetors mix the air and gas and don't need an electronic brain to tell them how to do it.

Using a carbureted induction is often the first choice for the budget-conscious builder, as there is no expensive EFI unit to purchase and tune. All you need are some basic parts to get going, and a few tuning passes often yield quick and impressive results. But we wondered if switching from EFI to carburetion, or building a carbureted combo from scratch, was really that simple. In the next few pages we'll answer those questions.

Before you venture forth with your project, consider that lopping off your EFI system is not an emissions-legal modification-unless your car was originally equipped with a carburetor, and in that case, you usually have to use 50-state-legal replacement parts. If you're looking at a strip-only project, then you don't have to worry about it.

That said, your project and your goals will ultimately determine the level of induction the engine will need in order to reach peak performance. You can almost always reach your goal with either EFI or a carburetor (or two), but there are some serious differences between the two systems, so the first thing to do is compare the components.

Many EFI engines that make over 500 hp require some type of enhanced EFI or a stand-alone engine-management system. This can cost well over $1,000 for a basic system and upwards of $2,000 for a fully optioned setup. You will also need a manifold, a throttle body, a mass air meter (save for Speed Density systems), fuel rails, injectors, a suitable pump and regulator, a good pressure gauge, and a feed and return system.

In contrast, a carbureted system requires only a pump, a feed line, a carburetor, and the manifold. Basic street/strip carbureted equipment costs far less than EFI parts, but once you get into hard-core racing parts, the price difference between EFI and carbureted components tends to get much closer.

One of the more important components to either system is the fuel pump. Electronically fuel-injected cars run at high fuel pressures, generally between 35 and 60 psi, whereas carburetors require anywhere from 5 to 9 psi. The high-pressure systems either employ a return line or an electronically regulated pump to control flow. There are in-tank and external pumps, and if you plan to make serious horsepower, you better plan to have a serious pump.

That said, it is best to get a fuel pump that is designed for a carbureted application when switching to carburetion. Aftermarket electric and mechanical fuel pumps are readily available from companies like Barry Grant, Holley, Aeromotive, and Mallory, and at times you can get away with the stock mechanical fuel pumps.

Keep in mind that if you choose to use a mechanical fuel pump, you may need a cam eccentric to make the pump work. The eccentric bolts on to the camshaft and manipulates the fuel pump's arm in order to produce the pumping action. An older block must also be used, as the EFI blocks have no provision for this pump. In high-performance applications, an electric pump is the better choice.