Hi Chris,
It sounds like your fuel pressure is overwhelming the ability of your
carb's float chamber to shut off the fuel flow. As the fuel bowl fills, a
float rises and presses against a float lever. This lever presses a spring
loaded needle valve that is tapered to a point, into the fuel inlet. If the
incoming fuel pressure is too high, it overcomes the ability of the float
bouyancy to exert enough pressure on the needle valve to stop the flow. The
excess fuel will then spill out the top.
Why one carb and not both? Perhaps the float lever of one carb is
misadjusted, allowing one carb to exert more pressure to close off the
flow. Or perhaps the rear carb float has a pinhole leak so it has reduced
bouyancy. Or the needle valve has some grit or gunk obstructing it from
closing completely, the flow being just what the engine wants at idle
unless you set the fuel regulator setting too high.
The only way to tell, is to open up the fuel bowls (4 screws on top). Be
ready with new gaskets, as the old ones may get torn up when you remove the
cover. Carefully grasp the float from both sides and ease it up and out.
Wipe it and shake it near your ear to listen to see if it has a leak and
took on fuel. Check the float lever for the proper setting. You should turn
the lid over, and use a ruler to set the appropriate clearance of about
9/16 inch from where the float contacts the lever to the lid.
Checking the needle valve is a bit more complex, and is best done by taking
the fuel bowl lid inside to a desktop. That way, if the retaining clip,
spring, or needle pops off you'll have a better chance of finding them! I
keep extras on hand, just in case I lose one. If you don't have extras, be
careful!
Good luck,
Fred - So.SF
BADROC
__________________________ Reply Separator _____________________________
>Subject: Temperature Gauge & Gas Overflow
>Author: "Chris Brucciani" <Chris_Brucciani@mminet.com>
>Date: 4/6/99 9:26 AM
>
>It was in the 80?s <G> this weekend here in Atlanta and while out running
>around in my 68 2000, I was watching the temp gauge and noticed that it
>fluctuated between 3/4 and 7/8 of the way up the temp gauge. (I don?t
>recall the degree figures). Is this normal, or am I running hot? Driving
>was variable stop and go with some short stretches in between.
>
>On a different note, I notice that gas sometimes runs out of the overflow
>tube of the carburetor closest to the firewall. I have an electric fuel
>pump installed by the PO, so I do not know the output pressure. I have one
>of those glass fuel filters with a removable cartridge, and have installed
>a fuel pressure regulator. I checked the float to see if it was leaking,
>and it is fine. I started the car and let it idle for a minute, and then
>gas started POURING out of the overflow! I shut it down, notched the
>pressure regulator back to a ?2? setting, and it seems fine. Something
>here is fishy. Any ideas? Is there a problem using this kind of filter or
>regulator setup? P.S. - Fuel Priced here are $1.14 for 93 Octane, and less
>than a buck for regular. Sounds good compared to out West!
>
>Lastly, another endorsement for Redline MTL in the tranny. Great Stuff!!
>Much smoother shifting and a lot less crunching! However, it does magnify
>any small leaks you may have. Thanks to all who post to the list, your
>help is much appreciated.
>
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