Step 3: Inspect Air Vent Tube Gasket A small gasket seals the vacuum port that provides vacuum to the pull-off piston inside the choke housing base. Any soft parts, such as O-rings, gaskets, and diaphragms should be replaced. Power Valve Testing Step 1:Separate Fuel Bowl from Metering Plate Use a nut driver or wrench to remove the four screws that fasten the fuel bowl to the carburetor. Take care to avoid burring the flats or damaging the metering block surface. Logic dictates that three carburetors would be fitted with main jets smaller than those fitted in a single carburetor on the same engine, since only a finite amount of fuel can be used by the engine. If the engine begins to stumble and dies, it is an indication that the power-valve diaphragm is not blown. Then, spray the dye onto the surface so that it penetrates into any existing cracks or pinholes.
Step 1:Remove Overflow Whistle Pin To remove the pin that secures the plastic overflow whistle, insert a flat-blade screwdriver into the rear of the cavity and pry upward to push the screw up. If any obvious damage such as pinholes, cracks, or tears, is evident, the diaphragm must be replaced. Parts will have to soak for a while, but will come out clean. Several small dowel pins locate the gasket. On Holley models with sight windows, the fuel level should just appear in the bottom of the window. Manifold Vacuum Holley power valves have a cast metal housing, a rubber diaphragm, and a spring.
Step 4: Inspect Metering Block Critical Inspection When you have a metering block primary side on all carbs, and on the rear of 4150 and 4500 carbs , no additional screws are present. The depth tip of a dial caliper or a dedicated depth gauge shown may be used. They are supposed to be open slightly for idle quality. Step 10: Select Accelerator Pump Cam Accelerator pump cams are available in different profiles for accelerator pump tuning purposes. Never, never use wires or drill bits or dental picks to probe into orifices, as they are carefully engineered to a specific size and shape.
Step 7: Drill Out Metering Block Plugs Professional Mechanic Tip Main and idle wells are capped with press-fit plugs. One small, thin metal sealing washer is under the screw head and one is at the bottom of the nozzle unit. Carburetor Renewal Kits Holley offers an extensive range of renewal kits, available for every model of carb that they make. Place all the parts of the carburetor in a cleaning tray. Located underneath the part number is a four-digit number, which indicates the build date.
When the dye has dried, run a fine flat file across the surface gently to reveal any low spots. This side-by-side comparison of fuel-bowl styles makes them easy to identify. Any detectable vertical movement indicates that the throttle shaft bearings are worn. As you proceed, check your filing with a straightedge and feeler gauge. Reinstall the bowl, and run the engine. You need to verify that it operates as designed.
Step 4: Remove Throttle Plate Screws Each throttle plate is secured to the throttle shaft with a pair of screws. The same problem occurs if the incorrect power valve is installed for the application. This kit is good for the carburetor numbers listed only. Then turn the knurled body of the tool to raise and remove the needle and seat assembly. It is screwed to the base of the float chamber where there is a little hole for gas to fall in. Keep the float and mounting screws together in a Ziploc bag to avoid losing the screws.
We are proud to announce the newest member of our carburetor family- the Street Warrior. But First Reread our Carburetor Theory Article Don't start until you re-read our Before working on one you must be familiar with how it works, so take the time now to get a thorough understanding of the technology. Carefully file it flat until the surface is uniform. Do not attempt to modify the gap to fully seat the throttle plates. A center-hung Nitrophyl float should weigh approximately 12 grams; a side-hung Nitrophyl float should weigh about 15 to 16 grams. If it is distorted or shows signs of unwinding, replace it. In the 1990s Holley continued its new product introductions.
The list number is assigned to a component as it is put into circulation this includes fuel pumps, ignition parts and other Holley products. Step 1: Select Main Jet Wrench Although a flat-blade screwdriver can be used to remove or install main jets, a much better choice is a dedicated jet driver such as those offered by Holley and a few other tool makers. Step 2: Remove Accelerator Nozzle Gasket Professional Mechanic Tip The discharge nozzle has two small, thin metal gaskets, one at the top between the screw head and nozzle and one at the base between the nozzle and main body. Check for warpage from front to rear and side to side. You can then determine if you have a faulty power-valve diaphragm and easily verify the level of vacuum when opening occurs. Baseplate Inspection You need to verify the integrity or flatness of the baseplate.
Lower the basket into the solvent bucket slowly to avoid splashing. In 1992, Holley began to include power-valve blow-out protection that was designed to protect the power valve and prevent diaphragm rupture. Some list numbers include letter prefixes. A handy window is built into the aluminum tester tool that allows you to visually check if and at what point the valve opens. The Carburetor Jets Every carburetor precisely meters the flow of fuel. Spray the entire exterior and interior of the carburetor with compressed air and carb cleaner spray.