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Hesitation at initial acceleration

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Old Feb 9, 2026 | 11:23 AM
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Default Hesitation at initial acceleration

I have a 78 L82 auto, low miles very original thus it has Q-jet. I have done a carb rebuild. So overall it runs fine but I have a hesitation when: from stop push on pedal and for about a 1/2 sec it accelerates just fine, then for about a 1/2 second there is a hesitation, then it is fine again. I have already replaced the accel pump so expect that is not the issue. Thoughts?
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Old Feb 9, 2026 | 12:00 PM
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Where did you buy the rebuild kit from?
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Old Feb 9, 2026 | 01:07 PM
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Originally Posted by greaser2
So I checked it without vacuum last weekend, 17 degrees at idle (800rpm) and 37 degrees at 3000 rpm.
Ignition timing sounds good from your thread from last year. How much is your vacuum advance adding though? And at what vacuum level is it all in at versus how much the engine produces at idle?

Too much vacuum advance can cause a bog off idle. And if it needs more vacuum to be all in than what your engine produces it will cause a “wandering” idle, as well as other issues.
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Old Feb 9, 2026 | 01:50 PM
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Originally Posted by 69L88
Where did you buy the rebuild kit from?
got it from cliff
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Old Feb 9, 2026 | 03:35 PM
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When you rebuilt the carburetor did you use Cliffs book as a guide?
Did you check the accelerator pump check ball at the bottom of the pump casting?
Did you polish the pump chamber?
Do you have the pump arm on the inner hole?
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Old Feb 9, 2026 | 06:31 PM
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Originally Posted by MelWff
When you rebuilt the carburetor did you use Cliffs book as a guide?
Did you check the accelerator pump check ball at the bottom of the pump casting?
Did you polish the pump chamber?
Do you have the pump arm on the inner hole?
I did not, I don’t recall such from speaking with Cliff
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Old Feb 9, 2026 | 07:19 PM
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Originally Posted by greaser2
I did not, I don’t recall such from speaking with Cliff
You may want to read this
https://www.themotorbookstore.com/how-to-rebuild-and-modify-rochester-quadrajet-carburetors.html?gad_source=1&gad_campai gnid=1806641261&gclid=CjwKCAiAqKbMBhBmEi wAZ3UboLxWjL8uRj_Eo7FlUgceLbNTJuRkL4t_SG iWV0TH2b6XNzHzHAi8jBoCytYQAvD_BwE

Last edited by MelWff; Feb 9, 2026 at 10:42 PM.
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Old Feb 9, 2026 | 09:35 PM
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Originally Posted by MelWff
You may want to read this
Book
thanks, I have a 79, is there something special about the 74?
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Old Feb 9, 2026 | 10:41 PM
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Originally Posted by greaser2
thanks, I have a 79, is there something special about the 74?
Sorry, somehow the wrong link was attached. I meant to attach a link to Cliff's book.


https://www.themotorbookstore.com/how-to-rebuild-and-modify-rochester-quadrajet-carburetors.html?gad_source=1&gad_campai gnid=1806641261&gclid=CjwKCAiAqKbMBhBmEi wAZ3UboLxWjL8uRj_Eo7FlUgceLbNTJuRkL4t_SG iWV0TH2b6XNzHzHAi8jBoCytYQAvD_BwE

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Old Feb 10, 2026 | 11:33 AM
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I had a blown diaphragm in my vacuum advance that made it do that also,
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Old Feb 13, 2026 | 09:02 AM
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I double checked the APT and it was at 2.75 turns out, moved to 4 out where the tip in is balanced and much better acceleration.
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Old Feb 13, 2026 | 12:56 PM
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Originally Posted by greaser2
I double checked the APT and it was at 2.75 turns out, moved to 4 out where the tip in is balanced and much better acceleration.
From Cliff Ruggles book

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