1973 Pontiac Grandville Rochester Carb

Tiny
NCATALUMNI03
  • MEMBER
  • 1973 PONTIAC GRANDVILLE
  • 7.5L
  • V8
  • RWD
  • AUTOMATIC
  • 51,000 MILES
Car is all of a sudden hesitating. It was driving fine now it hesitates when I press the gas. Carb was rebuilt last year and was running fine.
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Tuesday, July 7th, 2015 AT 1:06 PM

5 Replies

Tiny
CJ MEDEVAC
  • EXPERT
HAS IT SET UP FOR ANY PERIOD OF TIME?

THE MEDIC
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Tuesday, July 7th, 2015 AT 3:04 PM
Tiny
NCATALUMNI03
  • MEMBER
Only like a month at the time
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Tuesday, July 7th, 2015 AT 4:21 PM
Tiny
CJ MEDEVAC
  • EXPERT
FUEL THAT HAS ETHANOL IN IT IS HARD ON RUBBER PARTS IN THE CARB, IF YOU HAVE A STEEL FUEL TANK, SITTING FOR LONG PERIODS WILL RUST IT UP INSIDE BIGTIME

CONCERN HERE MIGHT BE THE "ACCELERATOR PUMP" IN THE CARB

IT'S SORTA A SUCTION CUP THINGEE THAT SQUIRTS A TINY STREAM(S) OF FUEL INTO THE CARB BARRELS WHENEVER YOU PUSH THE PEDAL TO ACCELERATE. THESE STREAMS "BOOST" THE BARRELS, UNTIL THE "ASPIRATION" PROCESS GETS CAUGHT UP.

ENGINE OFF! WITH A FLASHLIGHT (NO LIGHTERS!) REMOVE THE BREATHER AND EYEBALL DOWN INTO THE CARB. ACTUATE THE THROTTLE ARM ON THE SIDE OF THE CARB, DO YOU SEE SOME NICE PERTTY SQUIRT GUN SORTA STREAMS GOING INTO THE BARRELS?

OTHER THAN THE CARB BEING MESSED UP (OR NOT)

A VACUUM LEAK MAY MAKE IT HAVE SIMILAR SYMPTOMS

KEEP US POSTED

THE MEDIC
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Tuesday, July 7th, 2015 AT 4:41 PM
Tiny
NCATALUMNI03
  • MEMBER
Thanks for the info! I was thinking vacuum leak also bc when I have the hood up and take the air filter and intake off I hear a hissing noise I don't know if that's just air sucking in or an actual leak. Also to fix the accelerator pump do you have to tear the whole carb apart. Should I replace with a Holley or edlebrock or stay Rochester
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Tuesday, July 7th, 2015 AT 4:45 PM
Tiny
CJ MEDEVAC
  • EXPERT
WITH THE BREATHER OFF, YOU CAN REALLY HEAR THE CARB SUCKING AIR BY THE THROTTLE PLATE.

AS FAR AS FINDING AN ACTUAL LEAK TRY THIS, LOOK UP/ DO A YOU TUBE SEARCH FOR "ERIC THE CAR GUY" ADD THE WORD "VACUUM LEAK" TO IT. HE'S THOROUGH AND SAFETY CONSCIOUS TOO

YOU MAY CAN REBUILD YOUR CARB

I INSTALLED A HOLLEY 390 CFM 4 BARREL CARB ONTO MY 1977 JEEP CJ-5s INLINE SIX CYLINDER. OF COURSE I HAD TO CHANGE MY INTAKE MANIFOLD.

EVERYBODY LAUGHED AT THE MONEY I SPENT, BUT I SWORE I WOULD SURPASS THE MPGs OF THE ORIGINAL CARB

TO ME, THE HOLLEY IS EZier TO CHANGE JETS AND ADJUST/ REPLACE THE FLOATS

ADVANCE AUTO PARTS KEEPS A GOOD MANY PARTS FOR IT

I PUT IT ON MY JEEP IN THE QUEST FOR BETTER MPGs, THE ORIGINAL CARB GAVE ME 15 MOST OF THE TIME, 16 HERE AND THERE. MY HOLLEY GIVES ME 18 IF I DRIVE SENSIBLY, IF I GET ON IT, I HAVE SOME POWER

I ADDED AN OXYGEN SENSOR AND AN AIR/ FUEL RATIO GAUGE, TO SPEED UP THE PROCESS OF THE TUNING. THIS SITE BELOW HELPED ME A LOT WITH JETTING AND SELECTION OF A POWER VALVE

http://www.bob2000.com/carb.htm

MAYBE THIS WILL HELP SOMEHOW

THE MEDIC

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Wednesday, July 8th, 2015 AT 6:20 PM

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