JET Performance Products, Import & Domestic Performance, Performance Kits, Fuel Systems, Transmissions

Carburetor Information & History

JET Fuel Systems History:

Jones Carburetion and Fuel Injection, founded in 1968 and was the first to modify the Rochester line of Carburetors. This included many classes of racing, such as stock and super stock, drag racing, show room stock road racing and sportsman circle track racing. Soon they were recognized as the source for modified Rochester, Holley® and Carter carburetors for street performance, Drag racing, circle track, road race, off road and marine applications. Jones's engineering background and long racing career quickly established him as one of the most recognized and respected sources of fuel systems design and engineering. During the 1970's several auto manufacturers turned to Jones for assistance in designing new, cleaner burning fuel systems for their new vehicles. Today JET Fuel Systems has grown with the changes in technology and still offers a full line of performance engineered carburetors for all applications. With dramatic changes of the last 25 years in cam shaft, cylinder head and manifold technology, the demands on fuel systems has changed significantly and JET has adapted to this new technology as it was developed.

Why Buy A Modified Carburetor?
When the factory designs a new vehicle, they design the carburetion EXACTLY FOR THAT SPECIFIC APPLICATION. Even small changes in the vehicle will call for a unique carburetor, such as a manual transmission versus an automatic, different gear ratio in the axle, or a difference in the type of emission equipment. When you modify your engine with aftermarket parts you have now created a need to correct the calibration in the carburetor, or in some instances, change the type of carburetor all together. In some cases, you can purchase a "universal" performance carburetor that may run satisfactory on some applications. The problem is that they are not calibrated and set up for any specific application and will rarely give you the maximum horsepower, torque, response, drivability and idle quality, hence the need for specified application modified carburetors.

Air Flow Facts:
The truth about CFM ratings and airflow may shock a few people and hopefully serve as a reality check for many. We are not the first people to make these facts known, but obviously by the advertising and claims made by many of our competitors, there are still many people who need to be clarified on some basic principals of airflow and carburetion. Airflow through a carburetor is controlled by two main factors. The first being the venturi size, second the throttle bore size. A 4779 Holley® 750 CFM factor rating has a venturi size of 13/8" (1.275) and a throttle bore of 1 11/16" (1.690). A 4781 Holley® 850 CFM factory rating has a venturi size of 19/16" (1.5625) and a throttle bore of 1 ¾" (1.750). The largest you can modify the 4779 venturi is the range of 1.450 of an inch while still maintaining a 1.625 throttle bore. These two factors make it simply impossible for the 4779 to ever exceed the 4781 in total airflow. Yet some carburetor modifiers claim airflow levels from a 4779 matching that of a 8896 Holley® 1050 CFM factory rating that has a venturi size of 1.690 and a throttle bore of 2.00 inch! The difference of the throttle bore is .310 inch! Simple mathematics dictates basic airflow capabilities!

The other not so obvious factor when comparing factory airflow ratings to the claimed airflow ratings of various carburetor modifiers is that the factory rates airflow while the carburetor is also flowing fuel! Fuel displaces air, thereby lowering the amount of total airflow. Carburetion Modifiers typically rate the carburetor airflow completely dry, flowing no fuel! That way a huge increase can be claimed while in reality only minor gains are truly capable. The true horsepower increases really come from correcting the fuel curve so that the engine receives the correct amount of fuel at every point through the RPM range and through various load conditions (AKA vacuum levels.)