Carb question
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 35
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Carb question
i now absolutely NOTHING about carbs. my '67 327/300 hp has a replacement holley carb 4 bbl. it starts and run fine, elect. choke works great, but it has a dead spot in the pedal until it gets really warmed up, hesitates badly until you get past that point. i have only had this problem in one other car a long time ago. what do i need to do to fix it?
....and don't say i need to ditch the holley carb! LOL!
....and don't say i need to ditch the holley carb! LOL!
Melting Slicks
Joined: Jun 2012
Posts: 3,115
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From: Wilton Ca.
You mention that the choke works great but, then go on to describe what seems to be an issue with the choke. "Dead spot in pedal until it gets really warmed up, hesitates badly until you get past that point" tells me the choke isn't operating properly. JMO
Gary
Gary
Race Director
Joined: Apr 2015
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From: Fresno California
I'd check the accelerator pump shot. A weak pump can go unnoticed warm, but is problematic on a cold or lukewarm engine. Very easy to change an accelerator pump diaphragm on a Holley, and a very common problem, as well.
Melting Slicks
Joined: Jun 2012
Posts: 3,115
Likes: 196
From: Wilton Ca.
So, to the OP:
To check the accelerator pump, remove the air filter. Then, looking down the carburetor throat (engine cold and NOT running) slightly move the throttle shaft forward thus, pushing the accelerator pump arm. You should see a little squirt of fuel at the jets. The further you push on the throttle the more fuel you should see coming from the jets.
If you experience the aforementioned then, I still say it's a choke issue. Good luck.
Gary
Team Owner
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From: Middle TN by way of KY, OH, VA, IL, CA, FL, NY, SC, HI
However, that it not the same as adjusted correctly, which matches the symptoms I see described.
Unfortunately, the english language is not written in computer code. One man's "works great" is another's "needs adjusting."
Le Mans Master
Joined: Nov 2015
Posts: 7,444
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From: Really Central IL Illinois
Both are possible, but the jury cannot decide until more information is provided on the replacement Holley, e.g., does it have a choke pull off (round canister on the pass side with a vacuum hose attached)?
How far does the choke plate close when cold? Sounds like a simple adjustment of the choke or pull off, but could be a lean fuel mixture (accelerator pump cam or adjustment).
Post a picture of the pass side of the carb.
Go to the Holley web site for help also.
How far does the choke plate close when cold? Sounds like a simple adjustment of the choke or pull off, but could be a lean fuel mixture (accelerator pump cam or adjustment).
Post a picture of the pass side of the carb.
Go to the Holley web site for help also.
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Drifting
Joined: Apr 2008
Posts: 1,540
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From: Lexington Park Maryland
OP....., your car is not a modern day fuel injected car where you hit the key and go. If it runs good when warmed up then you don't really have a problem. I've never had the choke hooked up on my car and it runs great (when warmed up). Having said that, I would check the accelerator pump because they are known to go bad. Follow the procedure Gary's 66 outlines in post #6. You may also be running on the lean side which is magnified when cold. Is the carb new out of the box or rebuilt? I also agree with R66 in post #8, we need more information....
Race Director
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there is also an accelerator pump adjustment. watch the video at about 1:28
1. With engine off, open throttle fully.
2. Attempt to slide a .015 feeler gauge between the accelerator pump arm on the bottom of the fuel bowl and the accelerator pump adjustment screw on the throttle linkage.
3. Adjust the accelerator pump screw if necessary to permit the feeler gauge to slide in.
1. With engine off, open throttle fully.
2. Attempt to slide a .015 feeler gauge between the accelerator pump arm on the bottom of the fuel bowl and the accelerator pump adjustment screw on the throttle linkage.
3. Adjust the accelerator pump screw if necessary to permit the feeler gauge to slide in.
Last edited by MelWff; Mar 17, 2017 at 01:55 PM.
Race Director
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From: Fresno California
With a properly adjusted carb, you should be able to push the pedal to the floor once, hit the key, and it should fire up immediately on fast idle (engine cold). This is with a car that is driven more than once a week. If driven infrequently, more cranking/pumping will be needed as the gas in the carb will have evaporated away to varying degrees. If you have to pump the pedal 3 times on a regularly driven car to get it to start, you have carb issues: accelerator pump, choke, or float level.
Team Owner
Joined: Apr 2008
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From: Middle TN by way of KY, OH, VA, IL, CA, FL, NY, SC, HI
Team Owner
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Army
I also forgot about the secondary lockout.... I don't recall the setup on a typical Holley but on most carbs if the choke isn't engaging the secondary lockout and all four barrels are trying to gulp gas at once on a cold car, that can sure cause a bog too...