Problem Setting Float Level on Holley 390
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Junior User
Joined: Apr 2004
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From: Kirkland, WA
Problem Setting Float Level on Holley 390
This weekend I installed a rebuilt carb purchased from a reputable online dealer. The truck runs decently, but not great. The two main problems are hesitation when accelerating and very high idle.
The idle adjustment is all the way down and it still idles high. I know that the first thing to do is to set the float level - that's where I run into a problem. I can't set the float level. No matter where I adjust it, fuel just flows out the top of the sight hole. The fuel pump is the stock mechanical pump to I figure fuel pressure is ok and not too high. I thought it might be the float valve, but there are two float valves right? - one for the primaries and one for the secondaries? Fuel flows out of the sight hole on both the primary and secondary. There are no vacuum leaks and all unused vacuum ports are capped off.
Any suggestions on what this can be?
Oh, one more thing, is there a specific vacum port on the carb that I should be hooking the vacuum advance to?
Oh, this is on my '86 F250 with I-6 300 and the carb is a Holley 390.
Signed - I'm stumped.
The idle adjustment is all the way down and it still idles high. I know that the first thing to do is to set the float level - that's where I run into a problem. I can't set the float level. No matter where I adjust it, fuel just flows out the top of the sight hole. The fuel pump is the stock mechanical pump to I figure fuel pressure is ok and not too high. I thought it might be the float valve, but there are two float valves right? - one for the primaries and one for the secondaries? Fuel flows out of the sight hole on both the primary and secondary. There are no vacuum leaks and all unused vacuum ports are capped off.
Any suggestions on what this can be?
Oh, one more thing, is there a specific vacum port on the carb that I should be hooking the vacuum advance to?
Oh, this is on my '86 F250 with I-6 300 and the carb is a Holley 390.
Signed - I'm stumped.
Laughing Gas
Joined: Jul 1999
Posts: 1,048
Likes: 22
From: Lacey, WA
Hi
Well I would start with the fuel level first. This MUST be corrected.
I wonder if the correct fuel valves were used in the rebuild. You may have to take off the bowl and inspect the valve. Work the float up and down and ensure the little valve operates correctly. I have even tryed to blow through the fuel line while operating the float to check this.
On a side note, keep in mind that when you are trying to adjust the fuel level "down" in the bowl it will take a while for an idleing engine to consume enough fuel to bring the level down to the new level. In other words you can't adjust the screw and then open the sight plug expecting a change. Idle the engine a few minutes, or take it for a short spin and then check the level. You could probably just get away with a few rev's of the motor for this also.
As for the vacuum question, there should be a port on the passenger side of the carb, in the front, sticking out sideways of the metering block. This is the "ported" vacuum source.
Hope this helps and good luck,
Lee
Well I would start with the fuel level first. This MUST be corrected.
I wonder if the correct fuel valves were used in the rebuild. You may have to take off the bowl and inspect the valve. Work the float up and down and ensure the little valve operates correctly. I have even tryed to blow through the fuel line while operating the float to check this.
On a side note, keep in mind that when you are trying to adjust the fuel level "down" in the bowl it will take a while for an idleing engine to consume enough fuel to bring the level down to the new level. In other words you can't adjust the screw and then open the sight plug expecting a change. Idle the engine a few minutes, or take it for a short spin and then check the level. You could probably just get away with a few rev's of the motor for this also.
As for the vacuum question, there should be a port on the passenger side of the carb, in the front, sticking out sideways of the metering block. This is the "ported" vacuum source.
Hope this helps and good luck,
Lee
New User
Joined: Dec 2004
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another holley trick is to check the air bleeds in the venturi. if the carb looks like it has been sand blasted, enough of the parnt casting may have been removed to open them up a bit and cause your idle problem. (would be a bit lean in the midrange, also) simply open the choke and look down the barrels for holes about 1/64 of an inch in size. they will be starin at you. to know you have the right ones, put your finger over them and the engine will climb in idle or fall on its face. climb is good, stumble is bad.
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Junior User
Joined: Apr 2004
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From: Kirkland, WA
Originally Posted by GeneStoner
Mind if I ask whom you bought your carb from?
HP Carbs (Ebay)? ACFI Remanufacturing? Other?
HP Carbs (Ebay)? ACFI Remanufacturing? Other?
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Junior User
Joined: Apr 2004
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From: Kirkland, WA
Originally Posted by GeneStoner
How did you deal with your throttle cable/linkage? Did the stock setup work for you even though the carb linkage on the 390 is next to the firewall?
I mounted the carb transversely, with the throttle linkage facing forward, primary bowl facing passenger side. The stock linkage and cruise control hooked right up, all I had to do was pick up a little ball-linkage adapter from the auto parts store. All is ok now.
I do't expect to have any problems with the way I have the carb mounted. I don't do any serious 4x4'ing or hard cornering. This is just my tow vehicle for my 21' toy hauler.
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Posting Guru
Joined: Aug 2002
Posts: 1,493
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From: Great NW
Just FYI, ya might want to check here:
http://fordsix.com/forum/viewtopic.p...er=asc&start=0
It deals with how a carb is supposed to be mounted on the OFFY DP manifolds. Assuming of course, you are running an OFFY manifold...
http://fordsix.com/forum/viewtopic.p...er=asc&start=0
It deals with how a carb is supposed to be mounted on the OFFY DP manifolds. Assuming of course, you are running an OFFY manifold...
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Junior User
Joined: Apr 2004
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From: Kirkland, WA
Originally Posted by GeneStoner
Just FYI, ya might want to check here:
http://fordsix.com/forum/viewtopic.php?t=13677&postdays=0&postorder=asc&sta rt=0
It deals with how a carb is supposed to be mounted on the OFFY DP manifolds. Assuming of course, you are running an OFFY manifold...
http://fordsix.com/forum/viewtopic.php?t=13677&postdays=0&postorder=asc&sta rt=0
It deals with how a carb is supposed to be mounted on the OFFY DP manifolds. Assuming of course, you are running an OFFY manifold...
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