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Ok, so last week, I took the fuel pump, etc off so I could put an oil pressure guage on my 68. In the process, i must have bent the fuel line just enough to open up a pinhole leak in the line running to the fuel pump (I have a 2 piece fuel line) and i had a pretty good gas leak. So today, I got a 12" long section of 5/16 hose and replaced the corroded part. It was corroded where it passes through the part of the body under the floor pan. Not sure what that is called. Anyway, when i started it up today, gas was coming up out of the vent on the secondary bowl. Surely that small section of rubber hose would not cause all of that. Any ideas? I have a clear gas filter on it just before where it goes into the carb and a factory rebuilt holley. It ran FINE before taking it apart.
 

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My holley does that alot. Mostly after car has sat a long time. Maybe dirt stuck under the needle and seat valve for the float. Use to take it apart and clean it but found you can blow air back down the tube and it cleared it out. Do not use high pressure because gas is going to go everywhere when you do that only just enough to push the gas backwards. May be a bad thing to do but it worked for me. Saved me a tow from a car show once.
 

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Throw it in the trash and get a Carter.
 

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The alcohols in gasoline damage the o-ring that seals the needle. This results in gas getting past the o-ring and flooding the float bowl even with the needle sitting on the seat. With some needle designs it eats the rubber tip of the needle itself. I have to replace the o-rings about once a year with Arizona gas blends.

On Carter/ Edelbrock carbs you will have similar problems if you let the fuel bowls dry out. The floats stick to the bottom of the bowls. The accelerator pump rubber piston starts to leak and you get a flat spot on acceleration. They are all good carbs, I can any of them run great, they are just not designed for modern gas.

Please send me all of you throw away Holley carbs.
 

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Throw it in the trash and get a Carter.
Yes get a Carter that will never work quite right. Over all reliability may be better but is it worth it? Carter carbs make the hair stand up on the back of my neck. In general when a needle and seat stick open after sitting for a long time hitting the bowl with a plastic hammer or screw driver handle will fix it right up. Oxygenated fuel will cause any carb to have problems over time as it eats rubber parts and causes corrosion.

Bill
 

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You can remove the needle and seat assembly and check the condition of the Viton needle very easily. Hold the nut on top of the fuel bowl with a box end wrench to keep it from turning and use a large blade screwdriver to remove the slotted locking screw. Now, rotate the nut CCW to back out the needle and seat assembly. Count the number of rotations so you can get the float height setting in the ballpark when you reinstall it. The depth of the brass needle and seat assembly in the fuel bowl is what determines the float level. Once the needle and seat assembly is removed, check to see if there is anything lodged between the rubber (Viton) needle tip and the brass housing. There is no rubber "O" ring described in the earlier post. Once you've checked to see that he needle moves freely in the brass housing and there is nothing preventing it from seating all the way, reinstall it with the same number of turns it took to remove it. Check to make sure that the paper gasket material on both the upper and lower surfaces of the nut are still in good shape and tighten down the locking screw. Start the car up and see if fuel is still gushing out of the vent tube. If not, put a bunch of paper towels under the fuel bowl and remove the float setting sight screw on the side of the fuel bowl. Start the car and check to see if fuel is dribbling out of the sight hole. When the float height is set perfectly, the fuel should be right at the bottom of the hole, but not dripping out. Keep raising or lowering the needle and seat assembly and checking the fuel level at the bowl sight hole until it is just right. Each time you have to tighten down the locking screw on top of the adjusting nut before you start up the car or fuel will spray out.

I've never seen the Viton needle tips disintegrate or degrade from using newer fuels. At least within a 5 year span after rebuilding the carburetor.
 

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You can remove the needle and seat assembly and check the condition of the Viton needle very easily. Hold the nut on top of the fuel bowl with a box end wrench to keep it from turning and use a large blade screwdriver to remove the slotted locking screw. Now, rotate the nut CCW to back out the needle and seat assembly. Count the number of rotations so you can get the float height setting in the ballpark when you reinstall it. The depth of the brass needle and seat assembly in the fuel bowl is what determines the float level. Once the needle and seat assembly is removed, check to see if there is anything lodged between the rubber (Viton) needle tip and the brass housing. There is no rubber "O" ring described in the earlier post. Once you've checked to see that he needle moves freely in the brass housing and there is nothing preventing it from seating all the way, reinstall it with the same number of turns it took to remove it. Check to make sure that the paper gasket material on both the upper and lower surfaces of the nut are still in good shape and tighten down the locking screw. Start the car up and see if fuel is still gushing out of the vent tube. If not, put a bunch of paper towels under the fuel bowl and remove the float setting sight screw on the side of the fuel bowl. Start the car and check to see if fuel is dribbling out of the sight hole. When the float height is set perfectly, the fuel should be right at the bottom of the hole, but not dripping out. Keep raising or lowering the needle and seat assembly and checking the fuel level at the bowl sight hole until it is just right. Each time you have to tighten down the locking screw on top of the adjusting nut before you start up the car or fuel will spray out.

I've never seen the Viton needle tips disintegrate or degrade from using newer fuels. At least within a 5 year span after rebuilding the carburetor.
Nice in depth info. To add to it, setting the rear bowl float level on carbs without rear idle circuits can be tricky because no fuel is being used. If the last adjustment made is lowering the float level the setting many be lower than you think it is. Best way around the problem I have found is to shake the front of the car side to side enough to cause any excess fuel to run out the check hole then recheck the level. It's a good idea to recheck the float level after a road test also. Setting the float level on Holley carbs is definitely a job where you need a fire extinguisher handy though I have never needed one. Seems if you have one you will most likely never need it. See Holleys method here, http://www.holley.com/data/TechService/Technical/Adjusting Your Carburetor.pdf

Bill
 

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I'd still go though and clean 'em up at some point Andy....probably getting to the point of needing it - EVEN CARTRERS need cleaning LOL. Todays fuels just don't have much shelf life and tend to varnish out and gum up the works. Any small motor guy can attest to that. Buy a rebuild kit that has the blue (no stick) gaskets too! You will no regret that - unfortunately the old gaskets stick like a muther hummer!! Getting the fuel bowl separated can be a challenge. I find clamping on half in a vise and using a rubber mallot/wood block and some love taps will get the job done. _Be sure to check the surfaces to warpage with a machinists rule or a known good straight edge......sometimes you need to emery cloth 'em a bit to true them up. Holley's are super easy to clean/rebuild.
 

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There is no rubber "O" ring described in the earlier post. .
Hmm... You had the rest of that right but I guess you missed seeing the o-ring that fails located right above the window you are telling him to look through to see if there is contamination:



There are actually a bunch of different version of the Holley needle and seat. I grabbed a handful to illustrate some of the differences.



There are a lot of different versions of this part. The Genuine Holley ones have the two widows at fight angles to each other, the cheapest ones, that usually come in genric carb rebuild kits, have the oval shaped windows. I prefer the square window ones (like Holley) but I have not found any significant difference between the Holley right angle entry and the more common same side window versions. Holley seems to sell the right angle configuration if you buy them individually, and the same side version in the rebuild kits. Holley also sells a steel needle version for use with exotic fuels. This might be the way to go, but they retail for over $40 each.

These are the ones I have been using, and they came in a Holley rebuild kit.
 

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Actually the rear barrels do use a small amount of gas at idle. What they don't have (in most cases) is an idle air bleed adjustment screw.

See page 3/25 of the Holley Tech book if you do not believe me.

If you look straight down at the carb you will see four air bleeds (tiny holes adjacent to the venturi) The one to the outside of the carb are idle air bleeds, the ones to the inside are the main air bleeds. This is where air enters the carb to mix with the gas to form an emulsified mixture.

I do agree that if you have the level set too high, the fast way to clear it is to give the car a little shake. That is good advice.

But if you find that the rear barrels are using NO fuel you have just located another problem to be fixed. When the gas is evaporating out of the carb, it tends to gum up the bleeds. Using the little red extension tube on a can of carb cleaner and blasting these bleeds out can make the engine idle a lot smoother, and fix the off idle stumble. Another clue is that you have to really adjust the idle screws out farther than about 2 turns.
 

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Hmm... You had the rest of that right but I guess you missed seeing the o-ring that fails located right above the window you are telling him to look through to see if there is contamination:

Ahhh, yes. Now I see what you were describing. The way I read your post, I thought you were trying to describe an "O" ring that "seals the needle" itself, as if describing a rubber tip seating against a rubber "O" ring. I didn't realize you were describing the "O" ring around the needle housing.
 

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It is an easy thing to look right past, but it is critical. The o-ring is supposed to keep the fuel going through the windows at the top of the needle / seat assembly. When the o-ring fails, even if the needle is solidly on its seat, the gas will flow down the out side of the assembly and fill up the float bowl. The leak can be slow enough that you might not notice it at first.

One other trick worth knowing: If there is trash in between the needle and seat, you can clean it up by removing the locking screw, and then sticking the extension tube on the can of carb cleaner down into the needle assembly. That way you don't even have to mess with the float level.
 

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One other trick worth knowing: If there is trash in between the needle and seat, you can clean it up by removing the locking screw, and then sticking the extension tube on the can of carb cleaner down into the needle assembly. That way you don't even have to mess with the float level.
Great tip! That would definitely be the first (and quickest) thing to try to find out if that's the problem.
 

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Actually the rear barrels do use a small amount of gas at idle. What they don't have (in most cases) is an idle air bleed adjustment screw.

See page 3/25 of the Holley Tech book if you do not believe me.

If you look straight down at the carb you will see four air bleeds (tiny holes adjacent to the venturi) The one to the outside of the carb are idle air bleeds, the ones to the inside are the main air bleeds. This is where air enters the carb to mix with the gas to form an emulsified mixture.

I do agree that if you have the level set too high, the fast way to clear it is to give the car a little shake. That is good advice.

But if you find that the rear barrels are using NO fuel you have just located another problem to be fixed. When the gas is evaporating out of the carb, it tends to gum up the bleeds. Using the little red extension tube on a can of carb cleaner and blasting these bleeds out can make the engine idle a lot smoother, and fix the off idle stumble. Another clue is that you have to really adjust the idle screws out farther than about 2 turns.
You could be right about the rear using fuel on all Holley's but the ones without rear metering blocks use fuel so slowly I get tired of waiting and shake the car. The bleeds you speak of are air bleeds I would guess and if they were plugged would make the mixture rich in the rear using fuel faster. Or are you talking about the idle ports themselves. BTW I never had the book you speak of. I did some searching, are you talking about this book? http://www.amazon.com/Holley-Carburetor-Manual-Haynes-Techbook/dp/1563920697 Never really had a need for additional info but I may be installing a 67 GT 390 Autolite Holley on the 289 in my 67 standard and the more info the better as some changes will be required.

Bill
 

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Yep, that is the book.

I try to always start too low and then bring the level up, but I agree on the give the car a shake to bump a little fuel out: fast, effective.

I became one with the carburetor trying to pass Arizona smog test with the CJ. I was told by the guys running the test that it would not pass the day it rolled out of the factory. It can pass, but it takes real finesse to get it right.
 
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