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Topic: hesitation of throttle

in Forum: C3 Engines

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hesitation of throttle (1/7)
1/26/10 11:22am

68shrk
Former Member
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winchester, VA - USA

Vette(s):
1968 convertible 327/350 4spd

Joined: 12/26/2009
Posts: 2

when i step on the throttle the engine has a large hesitation, like it is choking, then it will kick-in. not very noticeable if the RPMs are kept high, but if there is a large jump in amount of throttle used it will hesitate....

it's a 350sb, bored 0.060, torquerII intake, mech fuel pump, 650 holley dbl-pmp carb, k&n air filter

any suggestions? thanks!!

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hesitation of throttle (2/7)
1/26/10 1:10pm

Gunslinger
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Frederick, MD - USA

Vette(s):
1969 convertible L71 427/435 4-speed black interior

Joined: 9/8/2003
Posts: 3398

How long has this been going on...recent or since the modifications were done on the car?

I would look first at the carburetor...double pumper could be putting too much fuel in the carb bowl on acceleration, it could need adjustment or even re-jetted to match the cam and intake combination. The floats could be out of adjustment as well. I'm not all that familiar with Holleys, but they're known for needing regular adjustments compared to Q-Jets or Edelbrocks.

The Torker intake is a single plane design, that will create some idle and low end acceleration issues compared to a dual-plane intake since it's designed as a high rpm intake, but a properly set up carburetor can less that effect.

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hesitation of throttle (3/7)
1/26/10 11:26pm

Adams' Apple

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20129

I'd definitely agree with a carb problem. Either the front accelerator pump is waaay too loose(starving for fuel), or it may have "squirters(discharge nozzles) that are too large(flooding).
It could also be a timing problem.
Does it backfire or anything like that, or does it just fall on it's face when ya goose it?

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hesitation of throttle (4/7)
1/26/10 11:37pm

dskopp
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Oak Creek, WI - USA

Vette(s):
1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

Joined: 5/21/2008
Posts: 1958

Yup, thats my vote also. Been there, dun that, got the t shirt for cab problems with my 81. The float in the carb was in really bad shape as well as various seals. My 81 hesitated real bad upon quick acceraration. Fell on its face and choked herself out. Much better after carb rebuild.dskopp2010-01-26 20:38:50

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hesitation of throttle (5/7)
1/27/10 6:17pm

lukesvette

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HOWELL, NJ - USA

Vette(s):
1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.

Joined: 5/18/2004
Posts: 6812

Do you have a friend with a vac secondary or Edelbrock carb? See a black cloud of smoke when you get on it from a stand still? I had a 69 Malibu with a very similar set up but had highway gears. Switched to a 650 Vac Secondary carb out of the box and cured the problem - I also think for initial acceleration, you're better off with a dual plane if you don't have the gears.

How big is the cam?

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hesitation of throttle (6/7)
1/27/10 8:41pm

KDADDY79
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Dutchess County, NY - USA

Vette(s):
White '79 Corvette. It's a driver.

Joined: 8/27/2007
Posts: 2484

I had an aftermarket air cleaner that interfered with the accelerator pump. Mine had the same hesitation you're describing. It wasn't on a Holley though, it was on my Q-Jet.

A GM aircleaner straightened it out. The clearance on the underside of it did the trick. (Thx. again DaveM!)

Kevin

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hesitation of throttle (7/7)
3/30/10 2:39pm

81zoomzoom
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Lusby, MD - USA

Vette(s):
1981 WHITE ALT WITH ALL THE BELLS

Joined: 10/18/2003
Posts: 56

Do your air/fuel screws work ok. Have you checked to see if the throttle plates are down on the transfer slots. If you have another carb. look at it and you will see what I'm talking about.

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