Maverick and Comet Repair

Fuel System

Motorcraft Variable
Venturi 2700W
For 1977, Ford's new 2700W (Variable Venturi) carburetor is available on California cars equipped with the 302 V8. Since the design of this carburetor differs considerably from the other carburetors in the Ford lineup, a little theory might be helpful here.

In exterior appearance, the variable venturi carburetor is similar to conventional carburetors, and like a conventional carburetor, it uses a normal float and fuel bowl system. However, the similarity ends there. In place of a normal choke plate and fixed area venturis, the 2700W carburetor has a pair of small oblong castings in the top of the upper carburetor body where you would normally expect to see the choke plate. These castings slide back and forth across the top of the carburetor in response to fuel/air demands. Their movement is controlled by a spring loaded diaphragm valve regulated by a vacuum signal taken below the Venturis in the throttle bores. As the throttle is opened, the strength of the vacuum signal increases, opening the Venturis and allowing more air to enter the carburetor. Fuel is admitted into the venturi area by means of tapered metering rods that fit into the main jets. These rods are attached to the Venturis, and, as the venturis open or close in response to air demand, the fuel needed to maintain the proper mixture increases or decreases as the metering rods slide in the jets. In comparison to a conventional carburetor with fixed Venturis and a variable air supply, this system provides much more precise control of the fuel/air supply during all modes of operation. Because of the variable venturi principle, there are fewer fuel metering systems and fuel passages. The only auxiliary fuel metering systems required are an idle trim, accelerator pump (similar to a conventional carburetor), starting enrichment, and cold running enrichment.

NOTE: Adjustment, assembly and disassembly of this carburetor require a number of special tools which are available only from your Ford dealer. Do not attempt to adjust or rebuild the carburetor without first purchasing the special tools.

ADJUSTMENTS
Before making any adjustments with the engine running, set the parking brake and block the wheels. Make sure the engine is at normal operating temperature and that any power accessories are turned off. Adjust the curb idle speed as you would on a conventional carburetor. Check the emission control decal under the hood for the proper speed.

Carburetor Adjustments

Year

Fuel Float
Level Adjustment
(in.. ± 1/32 in.)

Fast Idle Cam
Index Setting
(in. ± 1/64 in.)

Anti-stall
Dashpot
Adjustment
(in.± 1/64 in.)

Choke Plate
Pull-down
Clearance
Adjustment
(in. ± 0.0100 in.)

Dechoke
Clearance
Adjustment
(minimum in.)

Automatic Choke
Thermostatic
Spring Housing
Adjustment

Carter YF-1V

1970	170 eng-7/32 200 eng-3/8		7/64	170 engs-0.225 200 engs-0.265	170 eng-0.28 200 eng-0.25	170 man trans-1-Rich 170 auto trans-Index all 200 eng-Index
1971	3/8	170 man trans--0.105 200 man trans--0.170 200 auto trans--0.140	without A/C 0.100	170 man trans--0.200 200 man trans--0.230 200 auto trans--0.200	170 eng-0.28 200 eng-0.25	Index
1972	3/8	170 man trans--0.105 200 man trans--0.170 200 auto trans--0.140	without A/C 0.100	170 man trans--0.170 200 man trans--0.230 200 auto trans--0.200	170 eng-0.28 200 eng-0.25	170 man trans--Index 200 man trans--Index 200 auto trans--1-Rich
1973	3/8	200 man trans--0.170 200 auto trans--0.140	without A/C 0.100	200 man trans--0.230 200 auto trans--0.200	0.25	200 man trans--Index 200 auto trans--1-Rich
1974	3/8	200 man trans--0.170 200 auto trans--0.140	without A/C 0.100	200 man trans--0.230 200 auto trans--0.200	0.25	Index

Carter RBS-1V

1970	9/16	0.115	without A/C 7/32	0.19	0.25	1-Rich
1971-72	9/16	0.115	None	0.19	0.25	1-Rich
1973	9/16	0.115	None	0.19	0.25	Index
1974	9/16	0.115	None	man trans--0.30 auto trans--0.19	0.25	Index ♠

Carter YFA-1V

1975	3/8 ♣	0.140	None	0.290	0.25	200 eng--Index 250 eng--2 Rich
1976-77	25/32	0.140	None	200 eng-0.260 250 eng-0.290 ♥		200 49 states--1 Rich 250 49 states--Index 250 California--2 Rich

Autolite (Motorcraft) 2100D-V2

Year

Fuel Level
(inches)

Float
Adj.
(inches)

Fast Idle Cam
Index Setting
(inches)

Anti-stall
Dashpot
Adjustment
(inches)

Accelerator Pump
Operating Rod
Position
(in overtraval
lever)

Automatic Choke
Thermostatic
Spring Housing
Adjustment

Choke Plate
Pull-down
Clearance
Adjustment
(in. ± 0.0100 in.)

1971	7/16	13/16	man trans--0.150 auto trans--0.130	without A/C auto trans-1/8	man trans--#3 hole auto trans--#2 hole	man - 1 Rich auto - Index	man trans - 0.170 auto trans - 0.150
1972	7/16	13/16	.0130	without A/C auto trans-1/8	#2A hole	1 - Rich	man trans - 0.140 auto trans - 0.150
1973	7/16	13/16	See Procedure	None	#2A hole	3 - Rich
1974	7/16	13/16	See Procedure	None	#2A hole	3 - Rich	0.160 ♦

Motorcraft 2150-V2

1975	7/16	13/16	See Procedure	None	#2 hole	3 - Rich	0.140
1976-77	7/16	13/16	See Procedure	None	#2 hole	3 - Rich	0.140

♠ Choke cap setting on carburetor D4DE--AAA is 1 lean
♣ Float level in 3/4 in on D5DE--NB carburetor
♥ Pull-down clearance is 0.230 in. on D6DE--BB carburetor
♦ Overrich choke setting -increase clearance in steps of 0.020 in
Lean choke settings-decrease clearance in steps of 0.020 in.

COLD ENRICHMENT METERING ROD
NOTE: This procedure requires special tools.

Remove the choke cap.
Install the stator cap (Tool T77L-9848-A) as a weight to seat the cold enrichment rod.
Install a dial indicator or equivalent with the tip on the top surface of the enrichment rod and adjust the dial to zero. Raise the weight slightly and release to make sure the zero repeats.
Remove the stator cap and reinstall it at the index position, the dial indicator should read to specification. If the rod height is not to specification turn the adjusting nut clockwise to increase or counterclockwise to decrease height.
Reinstall the choke cap at the specified setting

CONTROL VACUUM

Install a tachometer.
Start the engine and set the idle to specification.
Using an alien wrench turn the venturi valve diaphragm adjusting screw clockwise until the valve is firmly closed.
Connect a vacuum gauge to the vacuum tap on the venturi valve cover.
With the engine at curb idle, use an allen wrench to turn the venturi bypass adjusting screw to reach the specified vacuum setting.
NOTE: It may be necessary to reset the idle speed while making the adjustment.
Turn the venturi valve diaphragm adjusting screw counterclockwise until the vacuum drops to the specified setting.
NOTE: It is necessary to cycle the throttle during this adjustment to get the vacuum to drop.
Check and/or reset the curb idle.

FAST IDLE SPEED
With the engine idling, EGR disconnected and the vacuum line plugged, make sure the fast idle lever is on the specified step of the fast idle cam. Turn the fast idle adjusting screw clockwise to increase speed and counterclockwise to decrease speed.

FUEL LEVEL ADJUSTMENT
Remove the carburetor upper body. Remove the old gasket and install a new one. Fabricate a gauge to the specified dimension. Check the chart for this.

Turn the upper body upside down and place the fuel level gauge on the cast surface, not on the gasket. Measure the vertical distance from the cast surface of the upper body to the bottom of the float. If it needs adjustment, bend the float operating lever away from the fuel inlet needle to decrease the setting and toward the needle to increase the setting.

CONTROL VACUUM REGULATOR (CVR) ADJUSTMENT
NOTE: The cold enrichment metering rod adjustment must be checked and/or set before making this adjustment.

Rotate the choke cap 180 degrees clockwise (rich) from index and cycle the throttle to set the fast idle speed cam.
Press lightly on the CVR rod. If there is any down travel, the rod is not seated and must be adjusted. If there is no down travel, turn the adjusting screw counterclockwise until there is some down travel and proceed with the adjustment.
Turn the CVR rod clockwise until the adjusting nut just begins to rise.
Again, press lightly on the CVR rod...if any spring-back can be seen the rod is not fully seated. Turn the adjusting screw clockwise in 1/4 turn increments until no spring- back can be seen.
Reset the choke cap to the specified setting.