That means floor it!
Turning the adjustment nut...
Turning the adjustment nut clockwise will lower the float level, while counterclockwise will raise the float level.
How To Set Float Level
One of the reasons Holley carbs are so easy to work on is because of convenience items like an externally adjustable float level. But apparently, this is also the cause of much confusion for entry-level (and perhaps not-so-rookie) car crafters. The process is very straightforward. The first step is to remove the sight plug from the side of the float bowl. With the vehicle at ride height, the float level should be just below the bottom of the sight hole so that slightly bumping the front fender will cause a small amount of fuel to dribble out of the sight hole. A too-high or too-low level can cause driveability problems and will certainly affect the engine's operational air/fuel ratio.
The tools you will need include a wide, flat-blade screwdriver and a 5/8-inch box-end wrench. If the float level is too high, fuel will spill out when the sight plug is removed. If this is the case, you will need to lower the float level by loosening the top locking screw with a screwdriver and turning the 5/8-inch adjusting nut clockwise (as if tightening). Give the nut a roughly 1/4 turn at a time and then tighten the lock screw. You should perform this procedure with the engine off. Replace the sight plug, start the engine, allow it to run for 30 seconds or so, and then remove the sight plug. If the fuel still runs out, repeat this process until the fuel level is just below the bottom of the sight plug. Do this for both the primary and secondary sides of the carburetor. Note that some Holleys do not use secondary bowl fuel for idle. This will require driving the car and actuating the secondary side of the carb to establish the true float level*. Make sure to work slowly until the float level is properly set.
Place the AN washer directly...
Place the AN washer directly underneath the spring clip. This will keep the shifter rattle-free and precise.
Hurst Shifter Tune-Up
If you've owned that Hurst Competition Plus shifter on your car for several years now and it seems a little less precise than it used to be, try this little tune-up. Purchase a new set of plastic inserts and spring clips from Hurst (PN 3320001, $9.95 from Summit Racing). Replace all the plastic inserts and place a thin, 3/8-inch-id AN washer on both ends of each shifter rod where it attaches to the shifter and to the pad on the transmission. Use new spring clips since the old clips tend to lose their tension after years of heat cycles. These AN washers are 0.060 inch thick and will fit just underneath the spring clip to keep everything tight and precise. You'll notice an immediate improvement in the quality of your shifts, especially if you take the time to precisely adjust the lengths of all the shift rods.
Manual Shifter Stops
If banging gears in your manual trans is your idea of too much fun, be kind to your transmission and make sure the stops are set properly on the shifter. The shifter stops are those bolt and nut arrangements sitting on the top of the shifter. With the shifter rods adjusted properly, place the shifter in Neutral and loosen the rear stop locknut. Place the shifter in Third gear and back the stop bolt off until it clears the shifter. Now tighten the stop until it contacts the shifter, then back the bolt off one full turn and secure the locknut to locate the stop bolt. Do this same procedure for the forward stop with the shifter in Fourth gear. Recheck the shifter operation. These stops prevent the shifter from overtraveling the shift rods inside the transmission, which could damage the trans. Double-check that the locknuts are tight, and you're ready to rock.