 This is one of four main metering...  This is one of four main metering jets in an Edelbrock/Carter carburetor. A vacuum-operated tapered rod (not pictured) fits into the jet to control fuel flow to the boosters. These carburetors have two jets for the primaries and two jets for the secondaries. |  When we speak of primaries...  When we speak of primaries and secondaries, we're talking throttle bores, barrels in shop slang. The two bores on the left are primary throttle bores, which are used in normal driving. On the right are two secondary bores which are opened mechanically or with vacuum when we mash the gas for more power. |  This is the view from above...  This is the view from above of a four-barrel carburetor with four throttle bores and four boosters. Again, we cruise on two barrels in normal driving and four barrels when the throttle is wide open. |
 Holley and Demon carburetors...  Holley and Demon carburetors have the power valve screwed into the metering block as shown. |  Here's a typical Holley, Demon,...  Here's a typical Holley, Demon, Autolite, Motorcraft automatic choke. Note the bimetallic coil inside the black, plastic cap. The fast-idle cam is a nylon part just below the choke mounting screw. Lean means bringing the choke off sooner. Loosen the three screws that retain the cap and slightly open the throttle to adjust the choke. You want the choke slightly closed. Be sure to adjust it with the engine cold, then check performance. If it is belching a filthy, rich mixture at the tailpipes, lean it out a little by opening the choke some more. |  This is an Edelbrock carburetor...  This is an Edelbrock carburetor choke in the cold-start position, partially closed to enrich the mixture. |