Carb question

[citiracer]

We fired up the motor this weekend and while idling, there was fuel dripping slowly out of the primary boosters. We shut it off and popped the site plug and fuel just poured out of it. We haven't adjusted the bowl level since last season so I don't think it's too high. Is this a bad needle valve?
I don't believe fuel pressure is an issue here. We're only running a 6-9 PSI pump.

[ljdardy]

same thing happened to me,changing float fixed it

[joedoozer]

Could be a few things but you are in the ballpark.

Needle could have a piece of dirt in it.

Also one of the air bleeds could have a piece dirt in it. Pull the bowl and metering block off and use some carb spray on the air bleed holes. Try and hold a nice white paper towel up to it, maybe you will get lucky and see it come out.

Some not so common problems could be the throttle shaft not having a good seal on one side.

Or the throttle plate is bent, pulling more air over one of the boosters. Making it look like its leaking. I have seen guys use a screwdriver down into the carb to hold throttle plates open. That could cause something like this.

[50j]

We fired up the motor this weekend and while idling, there was fuel dripping slowly out of the primary boosters. We shut it off and popped the site plug and fuel just poured out of it. We haven't adjusted the bowl level since last season so I don't think it's too high. Is this a bad needle valve?
I don't believe fuel pressure is an issue here. We're only running a 6-9 PSI pump.

If it sat all winter it could be a needle and seat. You might want to put a fuel pressure gauge on the car too just to check. I've had pumps put out more than they're supposed to.

[Earl Parker II]

If you're using Holley 6-504 needle & seats, the ID is .110". The most pressure they will reliably seat against is 6 psi. At 7 psi - 9 psi it will do exactly what it's doing. Anything over 6 psi is too much fuel pressure- the carb will be impossible to tune accurately and on track performance will suffer greatly.

I'd recommend checking your pressure with a good gauge. I'm betting it's high- if so, get a Holley 12-804 fuel pressure regulator and plumb it into the fuel line before the carburetor but after all filters. Set the pressure at 5.5 psi- provides a little cushion and will flow plenty of fuel for WOT operation. You'll be amazed at how much better it performs.

[dynoman14]

EPII is right on.

If you want to do a quick check on float level you can pull the bowl and flip it upside down and measure from the top of the float to the roof of the bowl, .400"-450" is pretty high, .500"-.550" is about average, and .600+ is pretty low. One flat on your adjusting nut is about .030". These numbers I have used for about 25 years, may not work for everyone, but I use it as a guide when evaluating float level settings. Special needle and seats and bent float arms will make a huge difference so you have to look at that also.

If you want to find out if you have a bad float, usually they leak from the solder that holds the 2 halves together on a brass float. I think they weigh about 15g new, if they are full of fuel they will be way heavy and not work.

New oxygenated fuels, e-85 and even pump gas is bad on carbs, I see 10 of them a day, If you want to prevent your needle and seats from premature failure, drain the bowls completely and lube them by removing the set screw and nut and spraying WD-40 down in there, takes a few seconds to penetrate but it will.

[Racedad]

Most likely as mentioned dirt in the needle valve.Another less obvious problem on the Holley carbs especially on one that has been sitting around is a bad o-ring on the outside of the needle valve.Extra fuel gets around it and into the bowl even though the float,float level,fuel pressure etc is all fine.

[citiracer]

We're putting a pressure regulator on it this afternoon. From everything I've read, if the pressure isn't right we're just wasting our time trying to tune elsewhere. Like trying to level the floors on a house with no foundation. So we're going to start there. Then just start all over with the tuning process.
* Set idle mixture based on vacuum
* Set bowls based on fuel levels
* Change the plugs and set jets based on how it performs and plug readings after first time out
* But PSI FIRST.

[citiracer]

Well before we installed the pressure regulator, we hooked gauge to the fuel log. Our pump that is supposed to be 7-8.5 PSI was cranking out 12.5 PSI.
We put the regulator on it and got it dialed to 5 PSI and now we can set the bowl levels and the thing runs like a scalded dog.

[Earl Parker II]

Isn't it amazing what just getting the basics down will do for you.