Holley Carb
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Cross-Country
Joined: Oct 2016
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From: Alabama
Holley Carb
On my truck I have a 302 engine with a 600 Holley. Everything is hooked up and the floats have been adjusted. I haven't, however, been able to fine tune anything because the idle will not go below 1600 rpm. It's like it is staying on high idle. The idle adjustment screw is turned out and so is the high idle screw behind the electric choke. Any thoughts on how I can get it to idle like it's supposed to?
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Joined: Jan 2001
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From: Virginia
First check for places air can get into the engine. Double check all the vacuum ports and vacuum lines, and double check the gasket underneath the carb.
If you are confident there is no air coming in somewhere else, the first thing I would do is go over to the pass side of the carb, on the secondary underneath the secondary diapraghm, and loosen that phillips screw to let the linkage relax and then tighten it. See if that makes a difference.
Is this a brand new carb or a used carb? Has it been rebuilt by you or someone else?
If you are confident there is no air coming in somewhere else, the first thing I would do is go over to the pass side of the carb, on the secondary underneath the secondary diapraghm, and loosen that phillips screw to let the linkage relax and then tighten it. See if that makes a difference.
Is this a brand new carb or a used carb? Has it been rebuilt by you or someone else?
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Well if you are sure both the idle speed screw and the choke fast idle screw are not hitting the stops I can only see it being 3 things
1- Disconnect the throttle and if it has it trany linkage from the carb and see if it idles.
2- A vacuum leak
3- Bent throttle blades
If the linkage disconnected did not lower it with the motor running at idle take your hand and start covering the carb and see what happens the more it is covered?
The other thing is pull the carb and with the blades closed how much of the idle slot do you see? Should only see a little hole not a slot.
Dave ----
1- Disconnect the throttle and if it has it trany linkage from the carb and see if it idles.
2- A vacuum leak
3- Bent throttle blades
If the linkage disconnected did not lower it with the motor running at idle take your hand and start covering the carb and see what happens the more it is covered?
The other thing is pull the carb and with the blades closed how much of the idle slot do you see? Should only see a little hole not a slot.
Dave ----
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Cross-Country
Joined: Oct 2016
Posts: 68
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From: Alabama
Holley Carb
Well it is a new carb so I shouldn't have to worry about bent blades. I have disconnected both the throttle and the trans kickdown. Both screws are backed out.
Still just idles at about1,649
Still just idles at about1,649
Post Fiend
Joined: Feb 2008
Posts: 5,831
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From: St Albert, Alberta
On my truck I have a 302 engine with a 600 Holley. Everything is hooked up and the floats have been adjusted. I haven't, however, been able to fine tune anything because the idle will not go below 1600 rpm. It's like it is staying on high idle. The idle adjustment screw is turned out and so is the high idle screw behind the electric choke. Any thoughts on how I can get it to idle like it's supposed to?
DO make sure the choke high idle cam has fully retracted. Other than that the suggestions provided should fix ya up.
FTE Legend
Joined: Nov 2015
Posts: 30,966
Likes: 4,130
From: Angier, NC
Then look for a BIG vacuum leak. At the base of the carb it may have a port for PCV hose if no hose make sure it is capped and if capped that it is not cracked. also check for any other hoses that may have been knocked off.
You did not post what intake you are using on this motor. Is it stock or after market?
Dave ----
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Joined: Jan 2001
Posts: 57,014
Likes: 2,751
From: Virginia
If this is a new carb, you have air getting in from somewhere. Take the carb off and hold it up high and put the gasket on it underneath and see if it covers everything. If you are using the factory spacer plate, it usually has a very large vacuum port on the back, make sure you are using it or it's plugged off.
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Logistics Pro
Joined: Sep 2011
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From: Algona,WA
Also make sure the secondary stop adjustment didn't get cranked way in by somebody... Been there done that.
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Cross-Country
Joined: Oct 2016
Posts: 68
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From: Alabama
Carb
Yep recheck the choke cam to make sure that is not hanging up.
Then look for a BIG vacuum leak. At the base of the carb it may have a port for PCV hose if no hose make sure it is capped and if capped that it is not cracked. also check for any other hoses that may have been knocked off.
You did not post what intake you are using on this motor. Is it stock or after market?
Dave ----
Then look for a BIG vacuum leak. At the base of the carb it may have a port for PCV hose if no hose make sure it is capped and if capped that it is not cracked. also check for any other hoses that may have been knocked off.
You did not post what intake you are using on this motor. Is it stock or after market?
Dave ----
ALSO, on another note, I have the AOD kickdown hooked up correctly and adjusted correctly, but the cable itself has a lot of resistance. I took the cable loose from the throttle and just pulled it by hand and it seems to have a LOT of resistance. It's enough to pop my cable stop for the throttle cable off of the cable. Any thoughts as far as that goes??
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Has the motor been rebuilt?
I ask because if rebuilt and the block decked & heads milled it can throw off the angle between heads & intake. It could also happen if not rebuilt.
This poor sealing could be at the bottom of heads and intake, making a vacuum leak inside the motor and hard to find.
You did say "it is smoking some" this could be a sign of a vacuum leak from inside the motor lifter valley area as it is pulling in oil.
Dave ----
I ask because if rebuilt and the block decked & heads milled it can throw off the angle between heads & intake. It could also happen if not rebuilt.
This poor sealing could be at the bottom of heads and intake, making a vacuum leak inside the motor and hard to find.
You did say "it is smoking some" this could be a sign of a vacuum leak from inside the motor lifter valley area as it is pulling in oil.
Dave ----
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Cross-Country
Joined: Oct 2016
Posts: 68
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From: Alabama
Has the motor been rebuilt?
I ask because if rebuilt and the block decked & heads milled it can throw off the angle between heads & intake. It could also happen if not rebuilt.
This poor sealing could be at the bottom of heads and intake, making a vacuum leak inside the motor and hard to find.
You did say "it is smoking some" this could be a sign of a vacuum leak from inside the motor lifter valley area as it is pulling in oil.
Dave ----
I ask because if rebuilt and the block decked & heads milled it can throw off the angle between heads & intake. It could also happen if not rebuilt.
This poor sealing could be at the bottom of heads and intake, making a vacuum leak inside the motor and hard to find.
You did say "it is smoking some" this could be a sign of a vacuum leak from inside the motor lifter valley area as it is pulling in oil.
Dave ----
FTE Legend
Joined: Nov 2015
Posts: 30,966
Likes: 4,130
From: Angier, NC
Ok on the black smoke when you said smoke I was thinking oil.
Even with the sealing flanges clean for a good seal if say the heads are at 25* and the intake at 35* that is a 10* gap left someplace that air/vacuum can get in causing a leak.
Do you have another carb to try to see if it is the carb?
I had an older Holley 600 that had an internal vacuum leak even after rebuilding. I replaced the carb and all was good don't know why the other had a vacuum leak?
Have you tried to cover / choke off the carb when running to see what happens?
Dave ----
Even with the sealing flanges clean for a good seal if say the heads are at 25* and the intake at 35* that is a 10* gap left someplace that air/vacuum can get in causing a leak.
Do you have another carb to try to see if it is the carb?
I had an older Holley 600 that had an internal vacuum leak even after rebuilding. I replaced the carb and all was good don't know why the other had a vacuum leak?
Have you tried to cover / choke off the carb when running to see what happens?
Dave ----
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Cross-Country
Joined: Oct 2016
Posts: 68
Likes: 0
From: Alabama
Ok on the black smoke when you said smoke I was thinking oil.
Even with the sealing flanges clean for a good seal if say the heads are at 25* and the intake at 35* that is a 10* gap left someplace that air/vacuum can get in causing a leak.
Do you have another carb to try to see if it is the carb?
I had an older Holley 600 that had an internal vacuum leak even after rebuilding. I replaced the carb and all was good don't know why the other had a vacuum leak?
Have you tried to cover / choke off the carb when running to see what happens?
Dave ----
Even with the sealing flanges clean for a good seal if say the heads are at 25* and the intake at 35* that is a 10* gap left someplace that air/vacuum can get in causing a leak.
Do you have another carb to try to see if it is the carb?
I had an older Holley 600 that had an internal vacuum leak even after rebuilding. I replaced the carb and all was good don't know why the other had a vacuum leak?
Have you tried to cover / choke off the carb when running to see what happens?
Dave ----
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Cross-Country
Joined: Oct 2016
Posts: 68
Likes: 0
From: Alabama
It slowly, very slowly, trickles down from that idle speed to lower and lower rpm until it almost dies