what is this tube for?

[Guest butlersZ]

Sorry guys that I don't have a picture but I'll try to describe it the best I can. I have a '74 260 Z with those damn flat top carbs and my mechanical fuel pump just went out, so I bought an adjustable regulator and set it at 1/2 psi and turned on my electric fuel pump. After the float bowls filled up gas started running out of this "tube" on the very front of the carb. The "tube" protrudes about a 1/2 inch out of the side of the carb into the inlet right before the choke butterflies. Is it an overflow tube of some sort or what? would drilling out the 1mm hole in the fuel return line to about an 1/8" or more help reduce the pressure?

[Guest rick458]

ButlersZ; that is the overflow tube 1/4 and beveled like a hypodermic needle right?. You are probably experiencing 1 of 3 problems.

 

(1) you have trash in the float valve/ incorrect float level [FSM says valve is not removable]

 

(2) a stuck air piston on the carbs [mine was and it squirted like a faucet]

make sure you have good oil in the reservoir and the damper rod isnt bent, unscrew the damper rod and stick your finger into the carb throat and using your finger tip try to raise the piston it should raise up pretty easy. If it is sticking pull the 3 screws off the top and remove it gently, pull the piston out and clean it and the needle, be VERY carefull the needle is about 3" long and there isnt a graceful way of setting the piston down. Use Berrymans B-12 to clean it all up and shoot the seat the needle sits in, Ease the piston back in place it has an index key and put the top back on.

 

(3) you are just overpowering the float valve it should handle 3 1/2 lbs

 

Hope that helps, I was glad when mine quit barfing gas all over the garage.

[Guest butlersZ]

thanks man, it helped alot to take off the carb tops and clean the pistons etc. I set my fuel pressure regulator to 3 1/2 psi and it works great!