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holley fans pls. read |
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4473 |
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Posted: Jan/31/2023 at 6:25pm |
replacing a couple of gaskets on the 4160s (crossram) today
and noticed on the p/s carb the primary butterflies are tilted a bit when cold. there is no choke. is this just to input a bit of air? should they be horizontal when cold? tia for any observations. |
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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mstrcrftr
Supporter of TheAMCForum Joined: Jul/12/2010 Location: houston Status: Offline Points: 2066 |
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yes, that is your idle speed air intake setting..
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7969 |
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Those slim rectangular openings in the throttle bore are the idle transfer slots. Like mstrcrftr said, they need to be partially uncovered by the throttle blades. They add idle fuel that isn't controlled by the mixture screws. When you turn the idle speed screw in to raise idle speed, the throttle blades open a bit and uncover the slots.
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4473 |
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so, i'm inferring that this visual is normal. thanks!
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7969 |
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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In your case wide open is normal, except when the car is sitting in your driveway.
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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BassBoat
AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1719 |
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at idle the transfer slot should just be exposed such that the slot looks like a square. Not much. Another Holley trick is to crack the secondary slightly, there is a screw that is accessed from underneath, so that the butterflies are all four, or in your case all eight, about the same. Easy to see if you hold the carb up to a light and look at the light around the butterflies. If you have to adjust the idle from that perfect square then the proper procedure is to either adjust the idle speed by using the secondary or drill holes in the butterflies. The transfer slot function makes a difference in the off idle and transition to cruise when you are just driving around. on a dual quad you might not care. I use a hex bit and box end wrench to get to that secondary idle stop screw. Not that you asked but a common issue with Holley accelerator pumps is the on line videos are mostly wrong. There should be NO slop in the accelerator linkage at idle let alone 0.015 gap as shown in the video. That gap is for wide open with the pump forced open to make sure you don't bottom out the pump.
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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To further add to what Bassboat is saying, the correct way to adjust your idle is to crack open those secondaries. There is a tiny set screw that can only be reached from underneath. The idle set screw should be at about 2-1/2 turns from the bottom, with about a half turn either way to adjust it. If it's more than that, the idle is too high to be adjusted only with the primary bores, it will need the flow from the secondaries. This leaves the fuel to be adjusted by the primaries and the transfer slots. The transfer slot should be a small square as mentioned. If it is more than that you are really transitioning into driving mode and it will idle rich and generally be difficult to adjust correctly. Opening the secondaries slightly will restore the air flow without having to open the primaries to the point where you are effectively running at part throttle, even at idle. This is not so important with a standard set up, but once you get into low vacuum/higher idle situations the primary idle speed set screw is not able to handle it without getting the transfer slots out of whack.
Chris PS: I would not drill holes in the throttle plate for the simple reason that it is not easily reversible. I guess it may be neccesary in extreme cases, but not often.
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4473 |
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did some reading about these slots. first, i don't have a bog to fix. second,
should the primary butterflies have a "square" of the transfer slot exposed? it seems all the fuss is about the secondaries. the current config for the primaries is no "square" slot. secondaries don't have one, either. the engine exhibits surging at idle--anything below 800 rpm, the idle increases, then decreases. i wouldn't mind idling at a lower rpm. is this because the primaries don't have the square slot at idle?
Edited by bikerfox - Feb/01/2023 at 11:31pm |
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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ccowx
AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
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Possibly. The idle transfer slots being too much (I assume) means that it is not well regulated for an idle and basically the idle mixture screws will be difficult to set because the engine is actually running basically in drive mode. This is where you have the secondaries cracked a bit so that you get the airflow you need for the idle you want. I wonder if you might be having mixture issues with the cross ram at idle? Or a vacuum leak? The cross ram gives many opportunities for those!
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