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Old 10-30-2021, 10:27 AM   #1
Marv 49
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Default Holley 885 leak down test

Still playing around with eliminating all the leaks from the carburetor on grandpas 49’. Last night i meticulously fiddled around with the float and got the fuel level to 1/2” below the top of the bowl (7/32 to both sides of the float). This morning i found it had leaked down about 7/16” of fuel out of the bowl. I expected this result after some reading I had been doing. I did not see any fuel outside the bowl, so that leads me to believe the power valve is the culprit. Is that a correct assumption and is there another way to test this theory? If the issue is with the valve, is there a replacement for this carb? My quick search for a replacement last night didn’t really turn up anything so what ever information you guys have would be appreciated! Thanks, Happy Halloween!
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Old 10-30-2021, 10:29 AM   #2
petehoovie
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Default Re: Holley 885 leak down test

Quote:
Originally Posted by Marv 49 View Post
Still playing around with eliminating all the leaks from the carburetor on grandpas 49’. Last night i meticulously fiddled around with the float and got the fuel level to 1/2” below the top of the bowl (7/32 to both sides of the float). This morning i found it had leaked down about 7/16” of fuel out of the bowl. I expected this result after some reading I had been doing. I did not see any fuel outside the bowl, so that leads me to believe the power valve is the culprit. Is that a correct assumption and is there another way to test this theory? If the issue is with the valve, is there a replacement for this carb? My quick search for a replacement last night didn’t really turn up anything so what ever information you guys have would be appreciated! Thanks, Happy Halloween!
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Old 10-30-2021, 05:49 PM   #3
mfirth
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Default Re: Holley 885 leak down test

Charlie NY is in here, give him a try. Also 51mercman may have a source.
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Old 10-30-2021, 06:55 PM   #4
tubman
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Default Re: Holley 885 leak down test

I believe member "Scicala" specializes in these carburetors.
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Old 10-30-2021, 08:33 PM   #5
scicala
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Default Re: Holley 885 leak down test

The power valve on the 8885FFC carbs are nothing like the later Holley 4 barrels and Holley 94's. If they are stuck open for any reason, it will not drain the fuel level down. This carb is virtually impossible for the bowl to leak down unless there is porosity in the bowl casting. I have heard of complaints about draining down, but can't really explain it. They also can't back feed fuel through the float valve, since it's above the fuel level. I blame it on fuel with ethanol ?

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Old 10-31-2021, 07:04 AM   #6
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Default Re: Holley 885 leak down test

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Modern fuel evaporates very quickly. In the past I've poured an inch of fuel into a small can and let it sit over night, then measured it in the morning to see how much had disappeared. It might work to do that with your carb and a small container of fuel side by side to see if that's what is happening.



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Old 10-31-2021, 08:11 AM   #7
Crankster
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Default leak down test

I would agree that modern fuel formulations evaporate quickly in carburetors that are open to the atmosphere. Before the advent of fuel injection and closed fuel systems generally the refineries or blenders tailored the fuel for seasonal or climatic conditions, this was measured by the vapor pressure or Reid Index. They probably still make seasonal adjustments to gasoline in the EFI era but nothing like what was required back when carburetors ruled the roost.

"Winter" gasoline in the fuel tank has a greater percentage of lighter, easier to ignite fractions such as Butane, than "Summer" gasoline, it will be especially prone to vapor lock.
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Old 10-31-2021, 09:23 AM   #8
rotorwrench
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Default Re: Holley 885 leak down test

I've had warped ones leak where the bowl attaches but they generally only leak while in operation when there is fuel and air flow since the design only lets fuel and air to flow down to the lower body when the engine is running. Heat can cause evaporation if the ambient temperatures are very high or the engine is running hot. Winter or cold weather blend fuel is very volatile and evaporates quickly as was already mentioned but that depends on the time of year. Cars can easily experience vapor lock if this fuel is used in warm weather.

It shouldn't take long to fill the bowl if the fuel pump is functioning correctly and the idle circuit will function as long as there is fuel feeding the circuit from the bowl. The accelerator pump will function as well but these old engines flood easily if they are cold. This link shows the function and the Lincoln Mercury Overhaul Manual for the 49 thru 51 cars is pretty good about all the 885 function and repair. http://oldcarmanualproject.com/manua...index_0015.htm
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Old 10-31-2021, 01:44 PM   #9
Marv 49
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Default Re: Holley 885 leak down test

Thanks for the knowledge fellas! I feel like I have all but eliminated all my other leaks the carb was experiencing. It took a lot several tear downs and patience. I may play around with it some more and see if I can determine where the fuel disappears to.
Other wins I had last night were finding the reason the car would rarely return to idle. The first issue was the throttle rod was rubbing the air cleaner, but mostly the issue was on the driver side of the block the arm was hitting the block. Really hoping for a test drive later today or tomorrow after work
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Old 10-31-2021, 03:33 PM   #10
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Default Re: Holley 885 leak down test

Where is "southern Illinois"? My brother lived in Virden and my wife lived in Hoyleton.
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Old 10-31-2021, 09:48 PM   #11
Marv 49
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Default Re: Holley 885 leak down test

A little farther south and east….Nokomis
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