Holley carb. adjustments ?
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Holley carb. adjustments ?
Ok, I'm completely frustrated with 'tuning' my Holley.
Yeah, I can get it running, etc. - but I'm looking for an 'optimal' setting.
How do you guys 'adjust' the floats properly ?
I went by the recommendations per Holley but I can't tell what's the 'right' level.
Also, I'm having trouble with the 'idle' being a little inconsistent. The 'idle' mixture screws are about 1-turn in and I'm not running a 'choke'. After the car warms up - every once in a while - it'll idle down in the 500 rpm range where it sounds like I'm running a 'race' cam. :confused:
Yeah, I can get it running, etc. - but I'm looking for an 'optimal' setting.
How do you guys 'adjust' the floats properly ?
I went by the recommendations per Holley but I can't tell what's the 'right' level.
Also, I'm having trouble with the 'idle' being a little inconsistent. The 'idle' mixture screws are about 1-turn in and I'm not running a 'choke'. After the car warms up - every once in a while - it'll idle down in the 500 rpm range where it sounds like I'm running a 'race' cam. :confused:
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: Holley carb. adjustments ? (verskel)
Suggest putting a vacuum gauge onthe intake to see what the vacuum is doing.
Incorrect carb settings as far as idle and float level. Assuming you have a 4150 or 60 set the float level so you have fuel in 1/2 of the sight hole. If the vacuum reading drops to a low level (below normal idle #'s) when it drops, you most likely have a hunting idle, or a lean out condition caused by lack of fuel. Again float levels then idle settings. Slowly (1/4 turn at a time) open up the idle screws until the highest vacuum reading is achieved. Then in a 1/4 turn. Now see what the stability of the vacuum is. If it still screws won't adjust out you may just have a carb that needs some help with a rebuild.
Incorrect carb settings as far as idle and float level. Assuming you have a 4150 or 60 set the float level so you have fuel in 1/2 of the sight hole. If the vacuum reading drops to a low level (below normal idle #'s) when it drops, you most likely have a hunting idle, or a lean out condition caused by lack of fuel. Again float levels then idle settings. Slowly (1/4 turn at a time) open up the idle screws until the highest vacuum reading is achieved. Then in a 1/4 turn. Now see what the stability of the vacuum is. If it still screws won't adjust out you may just have a carb that needs some help with a rebuild.
Melting Slicks
Joined: Dec 2000
Posts: 2,635
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From: Union Ontario
Re: Holley carb. adjustments ? (verskel)
I was always told to take out the sight plug on the passenger side of the carb and adjust until the fuel just dripped out.
As for adjusting the carb, if its a vaccuum secondary carb, you can change the spring s in it and cange when your secondaries kick in. You can change to accelerator pump cams also(primaries and secondaries on mech. secondary carb). Past that you have to change the jets.
My Holley also sometimes will all of the sudden idle really low too, I haven't been able to tune that out of the carb
As for adjusting the carb, if its a vaccuum secondary carb, you can change the spring s in it and cange when your secondaries kick in. You can change to accelerator pump cams also(primaries and secondaries on mech. secondary carb). Past that you have to change the jets.
My Holley also sometimes will all of the sudden idle really low too, I haven't been able to tune that out of the carb
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Re: Holley carb. adjustments ? (MikeC)
Thanks for the help guys - re-adjusted the carb. yesterday & it's a lot better.
The car also starts easier without using the gas pedal too much. :cool:
MikeC - First I re-adjusted the Idle Mixture screws (since most of my problems are coming from idle). I had to 'match' both sides of the carb with 1 1/2 turns out (at low idle 2 turns caused the engine to stumble a bit.)
Next I adjusted the floats per your recommendations with gas just barely seeping out of the sight hole.
Wow, what a difference. There's nothing like the feeling of getting the carb. right ! :chevy ....now (when hot) I just turn the key and it starts +plus idle at stop signs is not 'erratic' anymore. :D
The car also starts easier without using the gas pedal too much. :cool:
MikeC - First I re-adjusted the Idle Mixture screws (since most of my problems are coming from idle). I had to 'match' both sides of the carb with 1 1/2 turns out (at low idle 2 turns caused the engine to stumble a bit.)
Next I adjusted the floats per your recommendations with gas just barely seeping out of the sight hole.
Wow, what a difference. There's nothing like the feeling of getting the carb. right ! :chevy ....now (when hot) I just turn the key and it starts +plus idle at stop signs is not 'erratic' anymore. :D
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: Holley carb. adjustments ? (verskel)
One of the mistakes that a lot of people make is to compare a Holley to a Q-Jet when adjusting the idle. A Q-Jet has corse thread idle screws and usually idles somewhere about 2 1/2 to 4 turns out. A full 1/2 turn is the norm. Holley's use a fine thread and a 1/8 to a 1/4 turn is all that is needed to make a change. Glad you make progress.
Burning Brakes
Joined: Mar 2002
Posts: 803
Likes: 0
From: South San Francisco CA
Re: Holley carb. adjustments ? (MikeC)
<<I was always told to take out the sight plug on the passenger side of the carb and adjust until the fuel just dripped out.>>
This is the way I do my 3X2 setup. Let the car idle and raise or lower the level by turning the big 5/8" nut on top of the float bowl. The fuel should just barely drip out of the bottom of the sight hole. The mixture is just a matter of best lean idle, usually somewhere between one and two turns from bottoming out. That's all I know about that.....
This is the way I do my 3X2 setup. Let the car idle and raise or lower the level by turning the big 5/8" nut on top of the float bowl. The fuel should just barely drip out of the bottom of the sight hole. The mixture is just a matter of best lean idle, usually somewhere between one and two turns from bottoming out. That's all I know about that.....
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Re: Holley carb. adjustments ? (fontking1a)
fontking1a - Thanks for the tips and I'm also thanking everyone who's tried to help me resolve this problem.
I ran the car today - and it sound & feels really solid.... no sputtering or idle variation, etc. - :D ...also a crappy carb. is really noticeable with a 4 spd M-21. :crazy:
It's a little low on the idle upon 'startup' - but I'm running without a choke - so I'll probably just adjust the butterfly a bit.... :yesnod:
My big Holley lesson ? - I was "overtuning" it - man you gotta be gentle.... those screws / floats/ idle, etc. is a lot more "touchy" than a Carter ! :lol:
I ran the car today - and it sound & feels really solid.... no sputtering or idle variation, etc. - :D ...also a crappy carb. is really noticeable with a 4 spd M-21. :crazy:
It's a little low on the idle upon 'startup' - but I'm running without a choke - so I'll probably just adjust the butterfly a bit.... :yesnod:
My big Holley lesson ? - I was "overtuning" it - man you gotta be gentle.... those screws / floats/ idle, etc. is a lot more "touchy" than a Carter ! :lol:
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