See Figures 1 and 2
Holley four-barrel carburetors first appeared on the Corvette in 1964. The 4160 used is an end-inlet carburetor, while the 4150 carburetors used have been both end and center-inlet designs. The secondary metering body on the 4150 carburetor is similar to the primary metering body. The 4160 secondary metering body is a cast body and a plate attached to the main body by six screws. The center-inlet 4150 has been utilized on the higher performance versions of the Corvette. In 1971, the Holley carburetor has revised calibration and a C.E.C. valve. Holley part numbers are located on the carburetor air horn.
The early model 4150 uses a bi-metallic choke mounted on the carburetor. It is correctly set when the cover scribe mark aligns with the specified notch mark. The later model 4150 and 4160 employ a remotely located choke. To adjust, disconnect the choke rod at the choke lever and secure the choke lever closed. Bend the rod so that when the rod is depressed to the contact stop, the top is even with the bottom of the hole in the choke lever.
Position the car on a flat, level surface and start the engine. Remove the sight plugs and check to see that the fuel level reaches the bottom threads of the sight plug port. A plus or minus tolerance of 1 / 32 in. is acceptable. To change the level, loosen the fuel-inlet needle locking screw and adjust the nut. Clockwise lowers the fuel level and counterclockwise raises it. Turn the nut 1 / 16 of a turn for each 1 / 16 in. desired change. Open the primary throttle slightly to assure a stabilized adjusting condition on the secondaries. There is no required float drop adjustment.
Fast IdleEARLY 4150 CARBURETORS
Bring the engine to normal operating temperature with the air cleaner off. Open the throttle. Place the fast-idle cam on its high step and close the throttle. Adjust the fast-idle screw to reach the specified idle speed.LATE MODEL 4150 AND 4160 CARBURETORS
Open the throttle and place the choke plate fast-idle lever against the top step of the fast-idle cam. Bend the fast-idle lever to achieve the specified throttle plate opening.
Adjustment should be made with the engine not running. Fully open and secure the throttle plate. Force the choke valve toward a closed position, so that contact is made with the unloader tang. Bend the choke rod to gain the specified clearance between the main body and the lower edge of the choke valve.
Turn off the engine. Block open the throttle and push down the pump lever. Clearance between the pump lever arm and the spring adjusting nut should be 0.015 in. minimum. Turn the screw or nut to adjust this clearance.
Secondary Throttle ValveLATE MODEL 4150 AND 4160 CARBURETORS
Close the throttle plates then turn the adjustment screw until it contacts the throttle lever. Advance the screw 1 / 2 turn more.
Air Vent ValveLATE MODEL 4150 AND 4160 CARBURETORS
Close the throttle valve and open the choke valve so that the throttle arm is free of the idle screw. Bend the air vent valve rod to obtain the specified clearance between the choke valve and seat. Advance the idle-speed screw until it touches the throttle lever then advance it 1 1 / 2 turns.
Vacuum BreakLATE MODEL 4150 AND 4160 HOLLEY CARBURETORS
Secure the choke valve closed and the vacuum break against the stop. Bend the vacuum break link to gain the specified clearance between the main body and the lower edge of the choke valve.
DISASSEMBLY & ASSEMBLY
Disassembly and assembly are similar for the 4150 and 4160 series carburetors although there are minor differences from model to model. The following is a generalized disassembly and assembly procedure for all Corvette, four-barrel Holley carburetors.
- Remove the primary and secondary fuel bowls, metering bodies, plates, splash shields, and fuel tubes.
- Disconnect the secondary throttle-operating rod from the throttle lever. Remove the secondary throttle-operating assembly and gasket from the main body of the carburetor.
- Remove the float hinge pin retainer and remove the float and spring from the bowl. If so equipped, remove the inlet baffle.
- Loosen the inlet needle and seat lock screw and remove the assembly. Remove the sight plug and gasket.
- Remove the inlet fitting(s), gaskets, fuel filter, and spring.
- On the primary bowl: remove the air vent assembly (except early 4150); remove the pump diaphragm screws and lift the pump housing, diaphragm, and spring from the fuel bowl; check that the pump inlet ball can move freely. Replace the bowl assembly if ball movement is restricted or if either the ball or passage are damaged.
- To disassemble the metering body (all except 4160 secondary), remove the main metering jets.
Use a one-inch, twelve-point socket to remove the power valves. On the primary side, remove the idle mixture screws and seals.
- On the 4160 secondary, remove the plate and gasket from the metering body dowel pins.
- On the early model 4150, remove the choke housing, retainer, and gasket. Remove the choke housing shaft, fast-idle cam, and choke piston.
- On late model 4150 and 4160 carburetors, remove the choke vacuum break disconnecting link, fast-idle cam, and choke lever.
- Remove the discharge nozzle, invert the carburetor, and shake the discharge needle out.
- Replace gaskets, seals, and small parts with those provided in the rebuilding kit. Reverse the disassembly procedure to assemble the carburetor.
CEC VALVE ADJUSTMENT
1971 Holley 4150 Carburetor
This adjustment is made only when it has been necessary to remove the throttle plate, overhaul the carburetor, or replace the solenoid. To adjust, warm the engine and place the transmission in Neutral for manual transmissions or Drive for automatic transmissions. If so equipped, turn off the air conditioner. Disconnect the vapor-canister fuel tank hose and remove and plug the distributor vacuum hose. Extend the Combination Emission Control (CEC) valve plunger until it touches the throttle lever and then adjust its length until the specified idle speed is reached.
An efficient carburetor depends greatly on careful cleaning and inspection during overhaul, since dirt, gum, varnish, water in or on the carburetor parts are mainly responsible for poor performance.
Carburetor overhaul should be performed in a clean, dust-free area. Carefully disassemble the carburetor, keeping look-alike parts segregated. Note all jet sizes.
The carburetor Specifications Chart at the end of the chapter gives the various carburetor applications. Determine which carburetor you are dealing with and refer to the following sections. The sections are divided by carburetor type.
Once the carburetor is disassembled, wash all parts (except diaphragms, electric choke units, pump plunger and any other plastic, leather or fiber parts) in clean carburetor solvent. Do not leave the parts in solvent any longer than necessary to sufficiently loosen the deposits. Excessive cleaning may remove the special finish from the float bowl and choke valve bodies, leaving them unfit for service. Rinse all parts in clean solvent and blow dry with compressed air. Wipe all plastic, leather or fiber parts with a clean, lint-free cloth.
Blow out all passages and jets with compressed air and be sure there are no restrictions or blockages. Never use wire to clean jets, fuel passages or air bleeds.
Check all parts for wear or damage. If wear or damage is found, replace the complete assembly. Especially check the following:
- Check the float and needle seat for wear. If any is found, replace the assembly.
- Check the float hinge pin for wear and the floats for distortion or dents. Replace the float if fuel has leaked into it.
- Check the throttle and choke shaft bores for out-of-round. Damage or wear to the throttle arm, shaft or shaft bore will often require replacement of the throttle body. These parts require close tolerances and an air leak here can cause poor starting and idling.
- Inspect the idle mixture adjusting needles for burrs or grooves. Burrs or grooves will usually require replacement of the needles since a satisfactory idle cannot be obtained.
- Test the accelerator pump check valves. They should pass air one way only. Test for proper seating by blowing and sucking on the valve. If the valve is satisfactory, wash the valve again to remove breath moisture.
- Check the bowl cover for warping with a straightedge.
- Closely inspect the valves and seats for wear or damage, replacing as necessary.
- After the carburetor is assembled, check the choke valve for freedom of operation.
Carburetor overhaul kits are recommended for each overhaul. These kits contain all gaskets and new parts to replace those that deteriorate most rapidly. Failure to replace all parts supplied with the kit (especially gaskets) can result in poor performance later.
Overhaul kits contain specific procedures for the model carburetor the kit applies too. Some carburetor manufacturers supply overhaul kits of three types-minor repair, major repair and gasket kits.
Minor Repair Kits contain:
Major Repair Kits contain:
Gaskets Kits contain:
After cleaning and checking all components, reassemble the carburetor using new parts, using the exploded views in the car sections, if necessary. Make sure that all screws and jets are tight in their seats, but do not overtighten needle valves into their seats or uneven jetting will result. Always use new gaskets and adjust the float.