Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSGMC1977FORWARD CONTROL 7.4L ENG VIN Y, AUTOMATIC TRANS, TRANS MFR CD 475/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE MECHANICALFUEL SYSTEMROCHESTER 4MC & 4MV 4-BARREL CARBURETORSCARBURETOR APPLICATION

1977 GMC Forward Control 7.4L Eng VIN Y, Automatic Trans, Trans Mfr CD 475/M40

Carburetor Application

1977 GMC Forward Control 7.4L Eng VIN Y, Automatic Trans, Trans Mfr CD 475/M40SECTION Carburetor Application

NOTE: SERIES IDENTIFICATION: The vehicle series numbers used in this article have been abbreviated for common reference to both Chevrolet and GMC models. Chevrolet models use numerical designations as listed; GMC models are identified as follows: 10 = 1500; 20 = 2500; 30 = 3500.

1975 GENERAL MOTORS CORP.

Application

Rochester Carb. No. Man. Trans.

Rochester Carb. No. Auto. Trans.

C10-30, K20-30

350" V8

Federal

7045213

California

7045583

G20-30

350" V8

Federal

7045214

California

7045584

P20-30

350" V8

Federal

7045216

7045516

California

7045586

P30 Motor Home

350" V8

Federal

.....

7045215

California

.....

7045585

G20-30

400" V8

Federal

.....

7045225

California

.....

7045588

K10-20

400" V8

Federal

7045229

California

7045589

C10-30 &

P30 Motor Home

454" V8

Federal

7045212

P30

454" V8

Federal

.....

7045217

GMC Motor Home

455" V8 ⁽¹⁾

Federal

.....

7045254

California

.....

7045554

⁽¹⁾	Model 4MC Rochester 4-Barrel. All others are model 4MV.

1976 GENERAL MOTORS CORP.

Application

Rochester Carb. No. Man. Trans.

Rochester Carb. No. Auto. Trans.

C10-30, K20-30

350" V8

Federal

7045213

California

7045583

G20-30

350" V8

Federal

7045214

California

7045584

P20-30

350" V8

Federal

7045216

7045516

California

7045586

P30-Motor Home

350" V8

Federal

.....

7045215

California

.....

7045585

G20-30

400" V8

Federal

.....

7045225

California

.....

7045589

K10-20

400" V8

Federal

.....

7045229

California

.....

7045588

C10-30 & P30 Motor Home

454" V8

Federal

7045212

P30

454" V8

Federal

.....

7045217

GMC Motor Home

455" V8 ⁽¹⁾

Federal

.....

7045254

California

.....

7045554

⁽¹⁾	Model 4MC Rochester 4-Barrel. All others are model 4MV.

1977 GENERAL MOTORS CORP.

Application

Rochester Carb. No. Man. Trans.

Rochester Carb. No. Auto. Trans.

C10-30, K20-30

350" V8

Federal

17057213

California

7045583

G20-30

350" V8

Federal

17057213

California

17057514

P20-30

350" V8

Federal

17057216

17057516

California

7045586

P30-Motor Home

350" V8

Federal

.....

17057215

California

.....

7045585

G20-30, K10-30

400" V8

Federal

.....

17057229

California

.....

17057525, 529

C10-30

454" V8

Federal

17056212

P30

454" V8

Federal

.....

17056217

GMC Motor Home

455" V8 ⁽¹⁾

Federal

.....

7045254

California

.....

7045554

⁽¹⁾	Model 4MC Rochester 4-Barrel. All others are model 4MV.

1978 GENERAL MOTORS CORP.

Application		Rochester Carb. No. Man. Trans.	Rochester Carb. No. Auto. Trans.
350" V8
	Federal	17058213	17058213
		.....	17058215
	California	17058513	17058513
		17058514	17058514
		.....	17058515
400" V8
	Federal	.....	17058229
	California	.....	17058525
		.....	17058529
454" V8
	Federal	17058212	17058212
	California	17058212	17058212

NOTE: Some 1978 models may use Rochester M4MC carburetors. See appropriate FUEL SYSTEMS article for service procedures.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.