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Old 12-20-2021, 10:10 AM   #1
CJStefan
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Default Holley 94 accelerator pump tuning

All of my carb rebuilding experience has been on the Rochester B and BC. That's probably the most straightforward carb on the planet, as it has like 15 parts. I'm rebuilding the 94 for for my '49 8ba and I see the accelerator pump bracket has 3 holes on it. Can anybody tell me exactly what moving the C link to a different hole does?
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Old 12-20-2021, 10:22 AM   #2
1952henry
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Default Re: Holley 94 accelerator pump tuning

Moving link to outer holes shortens or lengthens the throw. Middle hole is the standard setting.
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Old 12-20-2021, 10:28 AM   #3
CJStefan
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Default Re: Holley 94 accelerator pump tuning

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Moving link to outer holes shortens or lengthens the throw. Middle hole is the standard setting.
Mine was set in the middle but why would I want to shorten or lengthen the throw? What would that affect as far as carb operation?

Last edited by CJStefan; 12-20-2021 at 10:45 AM.
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Old 12-20-2021, 10:46 AM   #4
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Default Accelerator pump tuning

Climatic conditions
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Old 12-20-2021, 10:55 AM   #5
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Default Re: Holley 94 accelerator pump tuning

Usually they are marked 1-2-3. I would imagine C stands for co;d and would provide a larger shot. Cold air is denser and so would require more fuel for a correct mixture.
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Old 12-20-2021, 11:12 AM   #6
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Default Re: Holley 94 accelerator pump tuning

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Ahhh so for summer run it in the middle or the lowest setting and for winter run it at the highest? On the 94 would adjusting the mixture screws work the same as moving the c clip? That's how the Rochester was adjusted for temp change
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Old 12-20-2021, 11:39 AM   #7
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Default Re: Holley 94 accelerator pump tuning

Right. Fuel being heavier than air, it tends to drop out at that moment of acceleration when the butterfly first opens, there will otherwise be a "bog" or hesitation without an extra squirt of fuel to compensate by the accelerator pump circuit, until everything gets caught up. In cold weather this pump shot needs to be richened further.
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Old 12-20-2021, 11:45 AM   #8
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Default Re: Holley 94 accelerator pump tuning

Is there a general temp range for each setting? With this becoming my daily driver and being in Maryland seeing below zero to above 100, that would be a huge pain to change that setting every time I drive.
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Old 12-20-2021, 12:07 PM   #9
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Default Re: Holley 94 accelerator pump tuning

I would think tweaking down to this degree would be different for each car. Kinda like how much choke to use on start-up. Each engine/carb is a little different. Just have to get to know what your engine likes.
Maybe adjust it in the fall for richer operation, and then re-adjust again in the spring.
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Old 12-20-2021, 12:07 PM   #10
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Default Re: Holley 94 accelerator pump tuning

With the quality of gasoline today, the original seasonal fine tuning of the accelerator pump is usually not an issue unless other factors are involved. I'd set it on the longest (rich) stroke and leave it.
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Old 12-20-2021, 12:15 PM   #11
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Default Re: Holley 94 accelerator pump tuning

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With the quality of gasoline today, the original seasonal fine tuning of the accelerator pump is usually not an issue unless other factors are involved. I'd set it on the longest (rich) stroke and leave it.
Would that be furthest left or right? I haven't taken a good look at it yet?
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Old 12-20-2021, 12:26 PM   #12
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Default Re: Holley 94 accelerator pump tuning

Per the 39 reference manual the #1 hole (left) is for summer # 2 (center) is for winter and # 3 is for extreme cold temp.
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Old 12-20-2021, 12:30 PM   #13
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Default Re: Holley 94 accelerator pump tuning

Sweet thank you sir. Is that info in the green bible as well?
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Old 12-20-2021, 12:54 PM   #14
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Default Re: Holley 94 accelerator pump tuning

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Sweet thank you sir. Is that info in the green bible as well?
I have not seen it in that book. Most carbs that you see have arm in middle hole.
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Old 12-20-2021, 12:56 PM   #15
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Default Re: Holley 94 accelerator pump tuning

Alright thanks for the responses everyone. I truly appreciate it. As of today I'm waiting for a new check ball for the accelerator pump well before I can finish putting the carb together. Damn thing fell out and onto the garage floor never to be seen again
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Old 12-20-2021, 03:44 PM   #16
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Default Re: Holley 94 accelerator pump tuning

Middle hole all 12 months....if you need that link e mail and I'll get one off to you pronto.
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Old 01-09-2022, 09:03 PM   #17
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Default Re: Holley 94 accelerator pump tuning

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Middle hole all 12 months....if you need that link e mail and I'll get one off to you pronto.
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Thank you sir I appreciate that. I have all the parts now. I was in the process of reassembling the carb and i noticed the pump only moves down like a half inch or so. After that the pump rod (not sure of the actual name but the rod that actually moves the pump) continues to move down but the pumps bottomed out. Does that sound right? I know the pump just gets you off idle and I admit I've never paid attention to how much it moves, I just figured it was more than that. I'm holding off on finishing the rebuild until I get this figured out.
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Old 01-09-2022, 10:55 PM   #18
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Default Re: Holley 94 accelerator pump tuning

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Originally Posted by CJStefan View Post
Thank you sir I appreciate that. I have all the parts now. I was in the process of reassembling the carb and i noticed the pump only moves down like a half inch or so. After that the pump rod (not sure of the actual name but the rod that actually moves the pump) continues to move down but the pumps bottomed out. Does that sound right? I know the pump just gets you off idle and I admit I've never paid attention to how much it moves, I just figured it was more than that. I'm holding off on finishing the rebuild until I get this figured out.
CJStefan, rebuild kits generally have parts for other carbs included. Accelerator pump rods being one of those, the longer rod is for the 94, I never knew what carb that short rod is for.
In one of your previous posts, you asked if adjusting the mixture screws would be the same as moving the C clip. The answer to that is no, those adjustment screws are for the idle circuit, not related to the accelerator circuit. Your best bet is to read the nomenclature of the 94 carb to understand the functions of the three different circuits and how they function in operation.
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Old 01-11-2022, 09:27 AM   #19
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Default Re: Holley 94 accelerator pump tuning

Mine is set in the middle the two outer settings are for hot or cold climate.
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Old 01-11-2022, 10:05 AM   #20
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Default Re: Holley 94 accelerator pump tuning

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Mine is set in the middle the two outer settings are for hot or cold climate.
How much does your accelerator pump move?
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