Acceleration hesitation

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Dec 24, 2009 | 03:10 PM

leetownreb

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From: Leetown WV

Acceleration hesitation

Even when warm, there is a slight hesitation when I press the accelerator pedal (about .25") and then she flies!! Everything seems to check out. Any suggestions? I know there is a myriad of possibilities but maybe one of you has the secret. Thanx.

Dec 24, 2009 | 04:10 PM

WhiteC3

Racer

Joined: Nov 2009

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From: Franksville Wisconsin

Accelerator pump working??? Not running take air filter cover off and have someone pump the gas pedal a time or two while you look down the primary carb barrels.If you see gas squirting your ok if not you need a accelerator pump.

Dec 24, 2009 | 04:53 PM

leetownreb

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From: Leetown WV

there's an initial gas squirt as soon as the pedal is pushed

Dec 24, 2009 | 05:41 PM

WhiteC3

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From: Franksville Wisconsin

Sounds good. It could be power piston adjustment. But to find out the top of the carb will have to be pulled or power piston spring could be weak. I'm sure one of the carb gurus will chime in soon. You are running stock Q-jet right?

Dec 24, 2009 | 06:26 PM

corvettedave383

Burning Brakes

Joined: Apr 2008

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From: Glasgow, Scotland

Ive had a slight hesitation before, for me its either been not enough initial squirt or too much, try a different coloured cam or different sized squirter

dave

Dec 24, 2009 | 09:23 PM

leetownreb

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From: Leetown WV

Quote:

Originally Posted by WhiteC3

Holley 600 cfm as far as I can tell. It's tuff when you buy a 30-year old car and the mods that were made are not passed on from one owner to another. Doesn't look too worn.

Dec 24, 2009 | 10:57 PM

mydejavooo

Burning Brakes

Joined: Oct 2009

Posts: 782

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From: Magic Valley ID

Could it also be a fuel pressure problem? I know from past experience that a tired fuel pump can also present problems like what you have described. Just a thought.

Trevor

Dec 25, 2009 | 12:42 AM

MN80Vette

Drifting

Joined: Sep 2006

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From: Columbus MN

Quote:

Originally Posted by leetownreb

Holley 600 cfm as far as I can tell. It's tuff when you buy a 30-year old car and the mods that were made are not passed on from one owner to another. Doesn't look too worn.

I have a 600 cfm Holley and had the same problem. I increased the size of the squirters and switched to a bigger accelerator pump cam. I bought a set of them and picked the one with the earliest and longest lobe. That worked for me. I think I switched to the red cam. My '80 is on a lift with our son's '63 Nova under it, so I can't get to the engine to check for sure.

Make sure your acc pump is adjusted correctly also. I switched from the original acc pump arm to the arm from a 50cc kit. MUCH better.

Last edited by MN80Vette; Dec 25, 2009 at 12:49 AM.

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Dec 25, 2009 | 01:53 AM

nitronick

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Quote:

Originally Posted by leetownreb

there's an initial gas squirt as soon as the pedal is pushed

Work the throttle through an entire stroke. There should be two solid streams into the primary barrels for the entire stroke.

Dec 25, 2009 | 01:11 PM

#10

leetownreb

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From: Leetown WV

Quote:

Originally Posted by nitronick

Work the throttle through an entire stroke. There should be two solid streams into the primary barrels for the entire stroke.

Streams last momentarily. Where does one get the squirters, etc?

Dec 26, 2009 | 01:08 AM

#11

MN80Vette

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From: Columbus MN

Quote:

Originally Posted by leetownreb

Streams last momentarily. Where does one get the squirters, etc?

Holley accelerator pump nozzles (a.k.a. squirters) are available at most auto parts stores that carry Holley carbs. Find out what size you have now and get a pair 2 sizes up. Summit has a bunch of them:

http://www.summitracing.com/search/?...0nozzles&dds=1

If your accelerator pump arm is plastic, you should replace it with a metal arm. The plastic arms are known to wear and deform.

http://www.summitracing.com/parts/PRO-67237/

You might want to pick up some cams too:
http://www.summitracing.com/parts/HLY-20-12/

Dec 26, 2009 | 03:27 AM

#12

73StreetRace

Burning Brakes

Joined: Aug 2005

Posts: 1,164

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From: Europe, France

Did you check your timing ?
Are you using vacuum advance ?
When you press the gas pedal, the vacuum can should quickly remove vacuum advance.
If you have working squirters, I would check timing first.

Dec 26, 2009 | 10:26 AM

#13

leetownreb

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From: Leetown WV

Appreciate the feedback. Will check out recommendations.

Dec 26, 2009 | 10:59 AM

#14

mds3013

Melting Slicks

Joined: Mar 2009

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If streams stop, that is most likely the prob. They should last like Nick said. That is where you should start. mds...

Dec 26, 2009 | 12:44 PM

#15

SteveG75

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Joined: Jun 2000

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From: FL

90% of percieved carb problems are really timing problems.

Dec 26, 2009 | 01:15 PM

#16

MN80Vette

Drifting

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From: Columbus MN

Quote:

Originally Posted by SteveG75

90% of percieved carb problems are really timing problems.

Check your timing first. That could save you the hassle of removing your carb. Changing to lighter springs in the distributor is easy. Make sure your dist weights move easily too.