Carburetor - Holley 1945 1-bbl Dodge Caravan I

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

APPLICATION

HOLLEY CARBURETOR NO. (3.7L V6)

IDENTIFICATION

The carburetor part number is stamped on the side of the carburetor, next to the solenoid bracket. The carburetor may also be identified by the tag attached to the carburetor.

DESCRIPTION

The Holley 1945 carburetor is a single venturi, concentric downdraft design with venturi completely surrounded by a single fuel bowl. The carburetor consists of the air horn, main body, and throttle body. Four basic fuel metering systems are used: idle and transfer, main metering system, accelerating system and power enrichment system. Fuel inlet and choke systems are also used.

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article, see appropriate TUNE-UP article.

FLOAT LEVEL

With air horn removed, turn main body upside-down with gasket installed. Hold a straightedge across main body, over floats, at point farthest from fuel inlet. Floats should just contact straightedge. (Scheme 328) To adjust, bend float tang on float arm that contacts fuel inlet needle.

Scheme 328

CHOKE VACUUM KICK

1. Open throttle and close choke. Close throttle to trap fast idle cam in closed choke position. (Scheme 329) Disconnect vacuum hose from choke vacuum diaphragm. Connect hand-held vacuum pump to diaphragm and apply at least 15 in. Hg.
2. Apply light finger pressure on choke shaft lever to compress spring in diaphragm stem without distorting linkage. Diaphragm stem reaches a stop as spring is compressed.
3. Measure choke vacuum kick specified clearance between upper edge of choke valve and air horn wall. Clearance can be measured using specified drill or pin gauge.
4. To adjust, bend diaphragm link at "U" bend. (Scheme 329) Check all linkage for freedom of movement. Remove vacuum pump and install vacuum hose on diaphragm.

Scheme 329

FAST IDLE CAM POSITION

1. Position fast idle speed screw on second step of fast idle cam. Apply light finger pressure on choke shaft lever to close choke valve. (Scheme 330)
2. Using specified drill or pin gauge, measure clearance between top of choke valve and air horn wall at throttle lever side.
3. If clearance is incorrect, adjust by bending fast idle cam link rod until correct valve opening is obtained.

Scheme 330

CHOKE UNLOADER

1. Hold throttle valves in wide open position. Apply light finger pressure on choke shaft lever to close choke valve. (Scheme 331)
2. Measure choke unloader clearance between top edge of choke valve and air horn wall at throttle lever side. Check clearance with specified drill or pin gauge.
3. To adjust, bend choke unloader tang on throttle lever until correct clearance is obtained.

Scheme 331

ACCELERATOR PUMP STROKE

1. Place throttle lever in curb idle position. Make sure accelerator pump rod link is installed in correct hole in throttle lever. (Scheme 332)
2. Measure length of pump operating link from center of rod in throttle lever to center of rod in accelerator pump arm. To adjust, bend accelerator pump rod at "U" bend.

Scheme 332

DISASSEMBLY

1. Perform disassembly procedure with carburetor on stand to avoid damage to throttle valves. Remove wire retainer and bowl vent solenoid. Remove solenoid idle stop.
2. Remove fast idle cam retaining clip, fast idle cam, and link rod. Remove rod from fast idle cam. Remove choke vacuum diaphragm, link, and bracket assembly. Disconnect diaphragm rod from slot in choke lever.
3. Remove nut and washer from throttle shaft. Note position of rod in throttle lever and record hole used for reassembly reference.
4. Remove air horn screws. Separate air horn from main body, tapping gently with plastic hammer or screwdriver handle if needed. DO NOT pry on air horn. Lift off air horn until power valve piston, accelerator pump and main well tube clear main body. Remove air horn gasket. NOTE: DO NOT use a metal gasket scraper on any carburetor surfaces. Use a nylon or hard plastic scraper as needed.
5. Remove accelerator pump rod retainer screw and retainer. Remove accelerator pump retainer screw and accelerator pump. Rotate pump rod as needed to remove from air horn. Remove pump rod grommet from air horn.
6. Remove 3 screws and power valve diaphragm assembly. DO NOT attempt to remove main well tube from air horn. Main well tube must be carefully blown out with compressed air from both sides of air horn.
7. Remove fuel inlet fitting from main body and separate gaskets. Remove float pin retainer, float pin and float assembly. Turn main body upside-down and catch accelerator pump discharge check ball and weight.
8. Remove main jet using a screwdriver with a blade at least 3/8" wide. Ensure screwdriver has a good square blade.
9. Carefully depress power valve needle with 3/8" wide screwdriver until screwdriver blade seats in slot in top of valve. Remove valve assembly. NOTE: Power valve assembly consists of needle, seat and spring. If replacement of any part is required, replace complete assembly. Service valve includes all components.
10. Remove 3 throttle body screws and separate throttle body from main body. Remove throttle body gasket. Remove idle speed screw from throttle body.
11. Center punch idle mixture screw housing 1/4" from end of housing. Drill through outer section of housing at punch mark with 3/16" drill. Pry plug out of housing and save for reassembly.
12. Turn mixture screw in until lightly seated, counting turns. Record for reassembly reference. Remove mixture screw and spring.

Scheme 333

CLEANING & INSPECTION

1. Use a regular carburetor cleaning solution. Soak components long enough to thoroughly clean all surfaces and passages of foreign matter.
2. DO NOT soak any rubber or plastic parts in cleaner, particularly choke diaphragm and heater. These parts are best cleaned with a clean cloth and/or soft brush.
3. DO NOT use drills or wire to clean jets or other passages.
4. If cleaner manufacturer recommends rinsing with water, hot water will give best results.
5. Blow out all passages with dry, compressed air.

REASSEMBLY

1. To assemble, reverse disassembly procedure. Use all new gaskets and seals. Ensure that gaskets fit correctly and that all holes and slots are punched through and properly aligned.
2. If excessive wear exists between throttle shaft and throttle body, throttle body assembly should be replaced. Manufacturer does not recommend installing a new shaft in old throttle body.
3. Inspect idle mixture screw. Tapered portion should be straight and smooth. Replace if excessively worn. Install mixture screw and spring in throttle body. Bottom screw lightly and back out number of turns recorded during disassembly.
4. Install new throttle body gasket on main body. Place throttle body in position and tighten 3 retaining screws to 30 INCH lbs. (3 N.m). Install accelerator pump discharge check ball and weight. Fill fuel bowl with clean fuel to check ball and seat operation.
5. Hold ball and weight down with brass rod. Place accelerator pump assembly in well and operate by hand. If no resistance is felt, check ball is leaking. Remove weight and leave check ball in place.
6. Using a small drift punch, lightly tap ball against seat to form a new seal. Remove old check ball and discard. Install new check ball and weight. Perform fuel leak test again.
7. If there is still no resistance felt, main body must be replaced. If resistance is felt, check ball is seating correctly. Remove check ball and weight. Install accelerator pump, pump rod and rod retainer in air horn.
8. Install power valve assembly in bottom of fuel bowl. Tighten securely. Ensure needle valve operates freely. Install main jet in main body. Install float pin in main body.
9. Place float assembly in float shaft cradle. Install float pin retainer. Check float alignment to make sure it does not bind against main body casting. Install new gasket on fuel inlet fitting. Install fitting in main body. Tighten securely. Check float level and adjust as needed.
10. Insert check ball and weight into accelerator pump discharge well. Position air horn gasket on air horn. Carefully install air horn on main body. Make sure accelerator pump cup is not damaged.
11. Install 7 air horn screws and tighten alternately in steps to 30 INCH lbs. (3 N.m). Install fast idle cam and link. Install choke vacuum diaphragm, solenoid idle stop, and bowl vent solenoid.

SPECIFICATIONS

CARBURETOR ADJUSTMENT SPECIFICATIONS