Zenith 35/40 Carb Fuel Return Valve Diaphragm

[karshack]

Hello All,

Glad to be joining this forum. Have had my 1967 250S since June last year. Slowly getting around to a number of issues. I have benefited from lots of advice here for which I am grateful. And I hope I can add some nuggets of learning to help others. This is my daily driver

Now, here's my problem:

Zenith 35/40 dual carbs (I've got the manual, thx) where the primary carb has the fuel return valve. There is a needle/piston in the valve assembly that has a diaphragm. My diaphragm has pinholes and therefore it allows gas to pour through it. That means gas is dribbling out of the bottom of the fuel return valve assembly when the motor is running - no matter what the rpm. I think this has gotten worse over the last month or so - - more gas flowing and stronger smells when driving.

I don't see any carb kits with this needle/piston with diaphragm. So, I wonder if filling the lower valve chamber with something like Permatex 85420 gas-proof sealant is the best answer, short of finding a new fuel return valve assembly.

I would love to get this solved sooner rather than later. Don't know if this is contributing to my low mpg (roughly 9 - 11 city/freeway, 70 mph no problem).

Thanks in advance