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What is oem carb?

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Deacon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deacon Quote  Post ReplyReply Direct Link To This Post Topic: What is oem carb?
    Posted: Jan/16/2021 at 9:17pm
Inherited a 74 Javelin with 360 4bbl Holly. I have done research, but still have questions. Is it the OEM carb? Does anyone happen to know what model of Holley. I don't want to change it, just be able to adjust it properly. Thanks
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Trader View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2021 at 10:07pm
Most likely a dealer/owner replacement.
On the horn (top) of the carburetor will be a "List-xxxx" #.
This will provide you with everything to research the carburetor.
In the day it was common for a dealer to replace the Motorcraft carburetor with a Holley. They had a good reputation, more technical support, and the average garage mechanic of the day could tune a Holley vs the Motorcraft.
AMC even lists Holley's that were acceptable as dealer installations in prior years.
A well functioning Motorcraft is a fine carburetor. Many just gave up on them as they didn't understand how to tune them, or just didn't like them.
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ccowx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2021 at 10:37pm
Just to be clear, the Holley is not stock or oem on the car, though it may have been considered a legitimate replacement by the factory, as Trader says. It was common as dirt to replace the factory carb with something else, either a Holley or a Carter. One other thing to check that might give you some idea of whether this carb was put on back in the day or years later is the date code, also likely on the air horn of the Holley. 

Chris 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2021 at 11:16pm
I believe the original carb would have been a Motorcraft 4300.
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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scott View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scott Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2021 at 5:06am
We would need your VIN # to determine what the original carb was on your 1974 Javelin. It could have been either a 2 or 4 barrel Motorcraft. As Cam mentioned, if a 4 V originally it would have been a 4300. If originally a 2 V, it would have been a 2100 Motorcraft. Then there were different versions of those carbs depending on the transmission.

I doubt the factory would endorse the use of a Holley back in 1974 for anything other than off road use only, such as performance use. They wouldn't want to run afoul of the tightening Federal emissions regulations. Yes, they showed a Holley in the Group 19 performance parts catalog, but by the mid 70's were they available, & would the factory suggest using them on a street car?

To tune the Holley for your Javelin, look for one of the Holley carb tuning books out there, & follow their instructions.


Edited by scott - Jan/17/2021 at 5:19am
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Deacon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deacon Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2021 at 11:21am
Thanks for your feedback. The vin does show that it is a 360 4V car. I just wasn't sure what was OEM. On to tuning the Holly. It's running very rich.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mmaher94087 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2021 at 8:01pm
Sounds like a blown Power Valve.  Easy to replace.  Common problem.
Mike
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinrev Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2021 at 8:45pm
Factory carb would be the Motorcraft 4300 with an 4TA4 tag (automatic) 4TM4 tag (manual).
74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384
70 AMX 360 4-speed (since 1981)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jan/19/2021 at 7:57am
1973 AMC 401 AutoLite 4300 for reference
360 very similar.
What is stamped on the choke horn of the Holley?
A simple test to see if the Power Valve is bad is to screw the 2 idle mixture screws all the way in and lightly seat them, usually it will keep idling that way if the power valve is bad or it will quit if the power valve is good.  High fuel pressure, high float setting, or bad needle and seat or needle and seat o-rings are other possible causes, as well as secondary idle speed screw closed to far and primary idle speed screw opened too far which over exposes the primary transfer slots causing a loss of control of the idle mixture by way of the idle mixture screws.










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