|Holley 4150 Carburetor Manual
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Fuel Bowl Pump Diaphragm (proper installation)
Before replacing the pump diaphragm cover, check for warpage by laying the cover on a sheet of emery paper which should be on a smooth surface. Remove the sealing bead, if any is present.
Place the diaphragm assembly on the cover, holding the pump lever arm against the diaphragm so that the diaphragm is flat. Don’t forget to install the spring into the bowl first. Install the cover and diaphragm on the fuel bowl and insert the screws finger tight. Release the lever, making certain the diaphragm is loose enough to flex without wrinkling at the edges, also the diaphragm must be able to be raised so that the flange of the steel diaphragm washer touches the inner surface of the cover. These two checks will assure maximum diaphragm travel. Tighten the four screws in two stages, 1/2 torque the first time and full torque on the final stage (5-8 lb. torque).
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Floats perform an important function in maintaining the correct level of fuel in the float bowl by opening and closing an internal inlet valve. If the float develops a leak, it will sink below its ideal level and excess fuel will enter the bowl. This causes the engine to run rich and probably causes leakage of gasoline out of the carburetor, increasing the risk of engine fires. In a carburetor rebuild be certain to examine the old float for damage or corrosion. You can also test your float for leakage to determine if it needs to be replaced. Repairing old floats is difficult, especially in light of the need to avoid increasing the weight of the float with the addition of solder. Adding weight changes the floatation characteristics of the float.
We have one of the Internet’s widest selections of floats including all floats that remain available and many that are extremely hard to find. We have floats for all of the major name brands of carburetors. These floats are made in the U.S.A. and designed and built to the highest quality standards, including both brass and nitrophyl floats. In some applications, both are available to choose between. We do recommend changing all old nitrophyl floats at the time of a carburetor rebuild, and many mechanics change all floats during rebuilds.
From Holley, Carter, and Motorcraft to Stromberg and Zenith floats, we have them all, including a wide selection of Rochester and Marvel Schebler floats. If it is time for a float replacement in your classic car, scroll our selection and find your carburetor float at a price that will make you smile.
Float Problems and Their Diagnosis:
With brass floats, the floating “pontoon” is typically constructed of at least two brass sections soldered together along a seam. Then a tiny hole used to equalize internal and external temperatures is soldered shut to complete the assembly process. Since all of these points are submerged in gasoline during engine operation, leakage problems can later occur at any place that was soldered. Repairing these floats is quite challenging and replacement is usually preferred unless the float is no longer available.
If your engine is the least bit hard starting after it has warmed up, or if your exhaust has a rich gasoline odor, you probably have carburetor problems, and a bad float is one of the possibilities. Other symptoms include poor gas mileage and, of course, if the engine is flooding.