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Old 06-10-2007, 05:36 PM
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holley leaking throttle shaft

Does anybody know the cause of a holley 4150(650 double pumper) to leak or drip gas out of the primary throttle shaft on the passenger side of the car when the engine is turned off. Is there a gasket or something inside of there that could be worn out. I have just rebuilt the carb but I did't get into it that far. Otherwise the carb seems to run great. Floats were set good, the back might have been a little high, but I wouldn't think that to be the problem.. I does have a little stumble/popping that goes on when you first nail it for a second then It takes off. I believe that will be fixed by changng the acc.pump cam to a faster shot though. But this gas leaking out the throttle shaft has me confussed and its gettin my intake dirty!! haha..


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Old 06-10-2007, 06:36 PM
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When the engine is off, there should be NO fuel going down by the throttle shafts. If there is, the needle/seat is letting fuel past and is raising the fuel level and it eventually will drip over in the nozzles and then down on the butterflies/shaft.

As far as a "seal" or something, no, there is nothing there.
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Old 06-10-2007, 06:48 PM
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I will try to lower the needle and seats down a bit then, but I still don't understand why it would be dripping there on the outside of the carb onto the intake.

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Old 06-10-2007, 06:55 PM
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It will drip out because the shafts are not truely "sealed" in the bore of the base plate. When the engine is off, there is NOT supposed to be any fuel in that area. It's either dripping from one or more nozzles or slowly running down and puddling on the butterflys and then dripping out where the shaft exits the base plate.

Mark
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Old 06-10-2007, 07:45 PM
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Quote:
Originally Posted by Jmark
It will drip out because the shafts are not truely "sealed" in the bore of the base plate. When the engine is off, there is NOT supposed to be any fuel in that area. It's either dripping from one or more nozzles or slowly running down and puddling on the butterflys and then dripping out where the shaft exits the base plate.

Mark

that makes sence!!! If its not the floats being to high what else could it be? Or is that the usual cause for it..


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Old 06-10-2007, 08:07 PM
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The floats would have to be excessivley high for this to happen. I'll assume you set them correctly.
Main causes would be:
1. Dirt/debris in needle/seat
2. Defective needle/seat
3. Excessive fuel pressure, over riding the float pressure on the needle.
4. Defective power valve, letting the bowl drain down through a bad/torn gasket.
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Old 06-10-2007, 09:20 PM
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Quote:
Originally Posted by Jmark
The floats would have to be excessivley high for this to happen. I'll assume you set them correctly.
Main causes would be:
1. Dirt/debris in needle/seat
2. Defective needle/seat
3. Excessive fuel pressure, over riding the float pressure on the needle.
4. Defective power valve, letting the bowl drain down through a bad/torn gasket.


)New needle and seat out of rebuild kit
)Stock fuel pump. was fine on the other holley 600 vac sec I had on it
)New power valve and gasket

Im going to reset the floats tomarrow. When I checked them the car wasn't level it was on a incline with the front of the car higher then the back and I believe the rear floats are to high so i will set them right and get back to you.
Hopefully it will work

Flaming79
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Old 06-10-2007, 09:28 PM
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That's actually a common problem on Holleys and some other models, my Son's 650 leaks so bad around the primary shaft that there's a slight whistle at idle.
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Old 06-10-2007, 09:29 PM
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That might help too.

One quick thing you can do is let it idle and re-adjust the floats. Then shut it off and see if the gas rises and comes out either of the sight plug holes. (put a rag around the carb! LOL) If any does, it's most likely the needle/seat OR could be a sinking float, but brass floats rarely leak.

Mark
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Old 06-10-2007, 09:43 PM
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Quote:
Originally Posted by baddbob
That's actually a common problem on Holleys and some other models, my Son's 650 leaks so bad around the primary shaft that there's a slight whistle at idle.

this one has a whistle at idle also
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Old 06-10-2007, 09:47 PM
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Quote:
Originally Posted by Jmark
That might help too.

One quick thing you can do is let it idle and re-adjust the floats. Then shut it off and see if the gas rises and comes out either of the sight plug holes. (put a rag around the carb! LOL) If any does, it's most likely the needle/seat OR could be a sinking float, but brass floats rarely leak.

Mark

I will try it sounds like a good idea..
If it was the back bowl to high is there any way the gas could make it to the primary shaft? I don't see how but there are alot a fuel passeges. Or would I just be looking at the front bowl.
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Old 06-10-2007, 10:23 PM
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If the gas is coming out of the front shaft, it's most likely the front bowl.
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Old 06-11-2007, 06:07 AM
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Grab the front bowl and see hot hot it is. With the float set a bit high, you can get what you describe. If the bowl it HOT, the fuel can percolate and cause the fuel to flow out the booster. Pull the air cleaner and use a flash light and LOOK into the carb. You will see where the fuel is dripping from.

ALWAYS set float levels while on a LEVEL surface. The other way is to pull the bowl and hold the bowl upside down.

The float top should be parallel to the bowl top. Then slightly incline it down about 1/8 turn on the needle.
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Old 06-12-2007, 12:17 PM
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Well I lowered the float level and it did stop leaking from the shaft and it also quite leaking from the booster so thats that fix, but after driving it around for a while the car wanted to die so we took another look at it and when we shut it off it started leaking from the same places. I'm going to pull it apart but I suspect that the float may have a hole in it causing it to sink. Are the floats Very difficult to change? It is a center hung brass float, the guy I got the carb from said he was having problems with it leaking gas down into the engine when it was shut off, which was washing by the rings and getting into his oil. Do I need any special tools before I pull the carb off to go through it? Thanks guys


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Old 06-12-2007, 09:34 PM
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Just pulled out the front float and held it down in a bucket of water, I didn't get no bubbles and it did not fill up,, so The sinking float is ruled out. I will look into the fuel pressure out of that fuel pump might be a little hi ?? i don't know.. Looks like one of those stock carter fuel pumps. ? came with the car> The needle and seats are new though ,so I'm guessing its not that.


Flaming79
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