New Holley carb won't idle down...

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,577
1,847
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Kearney, NE
Here is Holley’s page on this carb.
The timed spark port is on the choke side of the primary metering block. That’s on page 4/14 in the instructions, but not in the quick start guide.
And according to the book’s pictures, the butterflies are black, not brass colored.
705BB29C-6BCA-4E77-8C78-65E8DC2784C3.png

It will be hard to really tune a carb car without a vac gauge and a timing light. and better get a VOM. It’s like OBD2 without a code scanner/reader.
 
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7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,577
1,847
194
Kearney, NE
AF8D0D6C-3DD5-4E19-B1CB-58988E0811B2.png

I did not make it to my off site storage today, but this carb off an 83 Mustang popped up. See how the linkage closes the secondary lever all the way? I wonder if your primaries are being kept open a bit so the similar link does not close all the way either. I’ll post for sure when I see my same model carb.
 

Mikesbaron

Member
Jun 1, 2019
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0
6
WA
Ok I'm 95% sure I figured it out. My "new" throttle cable mount was ever so slightly pulling on the throttle linkage, thereby opening the primary butterflies. Not only that but the stud on which I mounted said throttle cable bracket was stripped and was slightly rocking forward every time I stepped on the gas pedal, thereby letting the throttle pull the butterflies open THAT little bit.

I took off the throttle cable and TV mount and am going to junk it and make this black billet jobber fit. I need some help figuring out if I can make the oem throttle cable fit, or if (and which) throttle cable setup and TV cable mount I need to make it work.
 

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Mikesbaron

Member
Jun 1, 2019
59
0
6
WA
Yes I see how your linkage is closing the secondaries all the way. I'll take another look at it once I get this throttle cable mount fixed. Also, sounds like I have the timed spark source vac tube on the Full Manifold Vacuum source, so I need to swap it. Do I just plug that Full Manifold Vacuum source since I have no cruise control or pump diverter?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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polk county florida
This paragraph is what most of the advice was based on.
Goes to show that you had/have more than one issue here, fixing the linkage and swapping the vac line for the distributor to the correct port should allow you to adjust the carb
"The car starts up fine but idles at 1800 RPM, and then every few seconds continues to idle up to and past 3000 rpm! It does this whether I have the throttle cable connected or not. If I blip the throttle it does nothing to idle it down. I've tried adjusting the curb and fast idle screw but it has no effect. The only way I can get the idle down to 1200-1400 is if I manual close the choke plate while it's idling"