Ford, Autolite, Motorcraft Metering Jet 120-4-46

1964 & newer models with 5/16" threaded end jets. This assumes you have a number matching carburetor. Some of the older 2100 & 4100 Autolites are much smaller. Typically 1963 and older (assuming you are 100% sure you know the year of your carb.). This type of 4100 will probably have a plastic lever going to the secondary diaphragm. This type of 2100 & 4100 jet can be found here.

Motorcraft main jets, 1100, 1101, 2100, 2150, 4100, 4300, 4350. Priced per each. 

Features

• Made in USA
• Number Stamped on Top
• Solid brass

Your old jet may have the size stamped on the top or side. 50f=.050, 50=.050

To determine if you have the correct jets in your carburetor, operate your vehicle for 20 minutes at sustained speeds. Stop and pull a plug. Gray - Good, Black - move down one jet size, White - move up one jet size. Do it all over again until you get a gray plug.

This assumes your engine and electrical system is in good running order.