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4 BBL Holley flooding

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wiscofoot View Drop Down
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    Posted: April-22-2018 at 12:24pm
I have had this happen to me twice now. After the boat runs for several minutes and I shut off the engine, fuel continues to flow through the fuel barrels and floods the carb. Is there supposed to be any fuel flow after it’s shut off? I am thinking it’s just the float stuck on primary side but not sure.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: April-22-2018 at 12:46pm
You'll probably find a variety of people with a variety of explanations ranging from

Debris between the inlet needle and seat

Float level

Too high fuel pressure

Angle of the carbburetor

Ethanol in the gas it's some people's reason for anything carburetor related.

Assuming it ran good before this started happening, and not knowing how long since the carburetor/fuel system has had any attention, I'd get a rebuild kit and clean the carburetor and also make sure that the fuel system has a good filter upstream of the carburetor to keep junk from getting into the needle and seat as a first step.

It's run for 40 something years without a wedge but some people like to run it more level with a wedge. Personal choice whether you do this or not

Your float level also probably didn't magically change on it's own, but you could adjust the front float a little lower if you felt like it.

Being a 76 you may have a carburetor with externally adjustable floats, a picture of the carb would be good. Take a picture of the front of the air horn with the list number to figure out the rebuild kit you'll need.

Like I said earlier, I'd start with a good cleaning and ensure you have a good filter in the system

Sounds like you survived the shaft job and are using the boat
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: April-22-2018 at 3:57pm
Posting photos on here is basically not an option for me. I can’t get intenet at my house (besides satellite) and my work pc will only run internet explorer and for some reason doesn’t like this site.

I followed the instructions for external float adjustment and found my fuel level to be too high and after some adjustment I have eliminated the fuel flow after shut off.

Link for Holley 4160 float adjustment video.

https://m.youtube.com/watch?v=LKEonVeOXco



Ken, I got the shaft alignment within “.002 and am absolutely thrilled with how the boat feels through the entire rpm range. Very grateful for the help and pressure to do it correctly. Bought a barefoot drop ski and a slalom ski that doesn’t have double boots at a garage sale yesterday so I might go for a quick set this afternoon.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: April-22-2018 at 5:09pm
Glad it turned out to be an easy fix, if the drips come back you might have to do a cleaning but it sounds like you're OK.

Good old external float adjustments went away on marine Holley's shortly after 1976.

And..................good job on the shaft
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: May-03-2018 at 5:47pm
Flooding issues came back. Boat was running a little hotter because of different thermostat. The float level was set correctly (fuel barely dribbles out of bottom of sight hole). After shutdown it's pissing out of the vent tube and the venturis. Do any marine carbs not have the J tubes on the vents? I will post the list number when I get home but I think the fact that it doesn't have the J tubes on the vents means its an automotive carb.

There is a small bit of fuel in the glass bowl that says "replace fuel pump if you see fuel here"

The flooding is always after operation usually after running it hard then stopping.

Where do you test fuel pressure? I think all my plumbing between pump and carb is rigid steel.

So Ken, you were right before how it could be a ton of different things. Too much fuel pressure, misadjusted or pitted float, fuel boiling because too much heat transfer etc or bad/dirty needle and seat. I will pull the needle out tonight and look at it.

Does fuel pump failure often result in excess pressure? If the fuel pump Is the source of all my problems can I rebuild the diaphragms and seals? Seems like overkill to buy a whole new unit when it is so simple.   Open for advice on this one because you guys are very helpful. There is a ton of stuff online about these carbs but I guess I just want someone to tell me the most logical way of going through and testing each step.   Most importantly I want to know the easiest way to test the fuel pump outlet pressure, I can probably rent a kit from one of the auto parts stores.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MourningWood Quote  Post ReplyReply Direct Link To This Post Posted: May-03-2018 at 7:59pm
Usually a fuel pump failure results in loss of pressure.
Maybe look at the easy stuff first:

Yes, if you don't have fuel vents that turn down, you may have a automotive carb.

You mentioned the boat ran hot...if you lowered the float levels too much, it can lean out the mixture, causing hotter running.

First, put the correct thermostat in and eliminate that issue.

Then, make sure the float settings are correct for marine, not automotive specs.

Maybe time to pull carb, clean, replace needles/seats, etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-03-2018 at 8:08pm
In 76 a Holley marine carburetor didn't have j tubes. They showed up later in the 70's. In 76 they had externally adjustable floats like yours does too, so there's a pretty good chance it's marine.

Your list number should tell. Some of those list numbers from back then are hard to look up these days but if you post it, it will help. If it's the original carburetor you'll probably find paint the same color as the engine on the carburetor because PCM painted them back then. I had a 76 that was dark blue.

That small bowl means you have an AC dual diaphragm fuel pump. If it has a little in it, I'd keep an eye on it. It's tapped into the area between the 2 diaphragms It means the main diaphragm has a leak and the second diaphragm is hopefully preventing gas from getting into the oil. Fuel pumps usually don't fail in the high pressure direction...............usually You can't get parts to rebuild the AC pump, you have to get another one.

You test the fuel pressure on the fuel pump discharge line to the carburetor.

You'll have to get creative and the easiest way is to use hose with a tee in it as a temporary setup

Don't be cheap, buy a compound vacuum gauge/fuel pump gauge kit.

Harbor Freight has one for around 15 bucks that works good and it works for checking your engine vacuum too.

You're right that I was right that it could be a handful of things

I think checking your inlet needle and seat is a good place to start along with making sure you have a good filter in the system so that there's not more junk coming along to do the same thing again after you cleaning job. Maybe this will be your problem,

Here's a link to the fuel pressure/vacuum gauge

link
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wiscofoot Quote  Post ReplyReply Direct Link To This Post Posted: May-04-2018 at 11:37am
Thanks, you are spot on. A few of the older guys I work with were muscleheads in the day and we reviewed some drawings and I have a pretty good handle on it all now. I was worried that I was boiling the fuel but the problem happened when it was dead cold. I can rebuild it myself, I just want to get the right kit. I don't think it is an issue of excessive fuel pressure.   I pulled the needle and cleaned the seat and it appeared to loosen up but when I was trying to get my float reset where I wanted it....FIRE. I had it put out within 2 seconds so no damage but now I have a "powder coated" engine and bilge.

The engine and valve covers are blue like you describe but the carb is not painted like that.

From the choke horn

D2JL 9510 E
List 6576
504
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-04-2018 at 12:17pm
List 6576 is definitely, 100%, absolutely and whatever other adjectives you want to throw in there a Marine Holley.

The original paint on the carburetor probably disappeared with a dunking in some good cleaner over the years or it may never have been painted.

By the way, that's a 600 cfm carburetor.

You say you have a 302, are you sure of that?

They normally came with a 450 cfm Holley.
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