Carburetor woes...step inside!

Trying to determine my issue here...I'm running a stock mechanical pump so no regulator. I've tried 2 different Holley 600 cfm carbs (on untouched the other rebuilt) Both will start the engine but within 5-20 seconds the secondaries start to just pour fuel (a lot), this continues for 20 or so seconds after the engine is shut off.

Figuring I have always had bad luck with Hollies I picked up a quadrajet. This one started fine, idle won't come down but response was there. Needless to say after 1 minute of running the quadrajet started pouring fuel, in the primaries! Same thing as the Hollies, but in the primaries rather than the secondaries.

I tried swapping out fuel pumps as well, all 3 carburetors still do the same thing. I'm completely stumped.

 

I don't know what you are running this on but let me relate a recent experience with you. It was a 235 stock rebuilt pump had to regulate it it was making a tone of fuel pressure.

before yoyu throw more money at it get a gauge on it and see what king iof fuel pressure you are putting out.

Something else to look at is if you are pumping trash up and blocking the needle open on the seat. Do you have a functional filter between the pump and the carb?

Form what you describe you are doing your standard flooding it.

 

Tell us more about your fuel pump...does it have two connections, or three? If it has three, is the byp*** plugged or is it connected to the tank return line?

Did you set the float levels on the carbs before installing them?

 

2 port fuel pump, its on a 267 Chevy, have a filter coming off the tank as well as the filter in the quadrajet. Tanks clean and I ran new lines should have no debris.

 

I guess you have pretty much ruled out **** in the needle valves, of course If it were me I would look anyway.

You next step is to check the fuel pressure and make sure that you are not over riding the needle with fuel pressure.

If that checks you need to check your float levels. You cannot make the ***umption that whomever the last person was to use or work on the carberators got it right. But I'll just about bet you are making too much fuel pressure for the floats.

 

I bought a new,not rebuilt Delco brand pump ,flooded the carb at idle,just over 9 PSI. Got another new Airtex pump,8 PSI.A regulator fixd the problem on the Edelbrock carb,they usually get into problems at over 5 PSI.Generally Holleys will tolerate 7-8 psi with no problems.You have br*** floats? Adjusting the dry float level with the bowl inverted and the float parallel to the bowl top and bottom? Try to lower it a bit more than you think you should

 

I've had both of the Holleys apart several times, every things clean/new. I've set the floats on both to no avail. I ran to the parts store and picked up a regulator a few minutes ago, cut down line pressure...however its still pouring out the secondaries. I'm about to throw the towel in on this one.

 

It doesn't make sense unless there is an electric pump in the fuel tank. Regardless, you need a fuel pressure gauge as your next step. They are cheap and easy to hook up.

 

Is fuel pouring out the venturi clusters? They are the only fuel opening on a 600 Holley secondary besides the idle circuit.And the cluster and the idle fuel pick up is higher than the float bowl so it needs pressure to push it out like you're talking about.
These are 4150 type with a secondary metering block similar to the front? Or 4160 with no secondary metering block?

 

Cut down the pressure to what? Did you take my first advice and find out how much pressure you had before you started throwing money at it?

You are at a stopping point until you find out what is wrong. You cannot find out what is wrong if you don't know what isn't wrong.

 

I pre-set the clearance on Holley floats at .425" with machinist "jo blocks".....

 

If fuel pressure is found to be fine you may have done like so many others have in trying to adjust needle and seat/float. You may have bent the tab coming off the float that the needle rides on. You can adjust the float to spec. all you want, but if that tab is not square to the needle it will not seat correctly.

 

Well I'm not entirely sure what the issue was, fuel pressure wasn't it though. Traded some parts for another new 600 Holley and all is well. I need to read through my Holley book one day and learn more about them. Just glad to have it up and running again.

 

Check the O rings on the adjustable needle and seat I never mess with the float adjustment on a carb thats set for awhile without having extra o rings.

 

Three different carburetors having flooding issues definately point to excessive fuel pressure.

I see you added a regulator. If this is one of the el cheapo 29.95 regulators, it may not help. Those we have tested regulate pressure by regulating volume. At full rated flow (maybe 10 gallons/hour?) the output pressure will be close to the pressure dialed. On lower flow rates, the output pressure will be closer to the pressure of the pump than the dialed pressure. Like the '****** suggested, get a fuel pressure gauge.

Jon.

 

You don't bend tabs on a holley, you move the needle and seat up or down.

 

Here is another thread that makes me want to set myself on fire.
How in hell can you decifer a flooding carb without a clue of fuel pressure going into the carb.

 

Exactly.

Who's on first base?

 

I was refering to when guy's screw in the adjuster so much that they jack up that portion of the float. So now when they go to adjust the float correctly, it no longer adjust's or works properly. Hope that makes more since as to what I was refering to.

 

That actually makes perfect sense, I never though about it that way.