My son just recently finished rebuilding his 289 from his "68" mustang. He replaced the old two-barrel carburateur with a four-barrel 1405 Edelbrock carburateur. All was well until he put it in my garage after about 20 minutes with the garage all closed up the car fill the space with a very strong gas fumes odor. We've replaced all the fuel lines and double checked them but still the fumes. He has determined that the fumes are coming from the carburateur itself AND IN HIS WORDS!!! "That’s normal for and old car" Although I'm a carpenter I had to through the "BS" flag. That's when the argument started.If any one can help me give my son a few mechanically intelligent suggestions, I would greatly appreciate it, and if you need any more info just ask. This is my first posting and I’m not sure if my e-mail will show up so here it is Meseabee@yahoo.com Thank you in advance

 

It shouldn't be from the carb. I'd recheck the fuel lines and the gas tank.. both where the lines come in and where the fill pipe drops down into the tank.

Edit.. ohh and this isn't 'normal' for old cars that are serviced properly

 

Adrenolin,
I just went out to the car and "hand over hand" touched the fuel line from tank to pump to carburateur, There wasn't so much as even a wet spot anywhere on it. I didn't smell any gas by the tank but it was strong when I popped the hood and even stronger still when I took off the air filter. Could he have adjusted the Carburateur wrong???

 

just curious, how strong is it? I have left a tank of gas open overnight after filling a lawnmower up and it still wasnt all that strong. I dont know much about carbs but is it possible that it is slowly leaking fuel into the carb and therefore letting it evaporate quicker?

 

ninteen66mustang,
I beleave that is what is happening. How do I stop it?!?!

 

Your fuel psi may be too high or your carb is malfunctioning. I believe it is your idle circuit that is leaking due to the higher fuel psi. You mentioned he put an Edelbrock 4 bbl on. Is it new or used? If it's used it needs a rebuild. Hard rubber needle seats will let fuel pass by also. If it's new maybe a fuel regulator will help. You may want to invest in a fuel psi gauge first and see what the reading is when the engine is off. Check it for leak down too. Please correct me if I am wrong.
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Very little if any fuel will continue to enter the carburetor after an engine (fuel pump) is shut off.

Without knowing how strong of an aroma we are talking about, what is normal is tough to determine. Some folks are very sensitive to the smell of gasoline while another person might not even be aware of an aroma.

In any case, a small drip of gasoline may vaporize so quickly as to be all but undetectable to sight and touch, but still foul the air with the odor of gasoline. Check for seepage anywhere a rubber line meeds steel. Seepage is common here.

 

I would like to know:
1) is it a brand new carb?
2) are you running a fuel filter?
3) what size carb?
4) does the car run and idle good?

-Gun

 

Sounds like the float isn't adjusted right and fuel is leaking down the intake. If so it should also be rich at idle.

 

I am the Mustang owner. The engine is newly built and it is about 300 miles into the break-in. The carburetor is brand new, and other than the idle fuel/air mixture, it has not been changed. I have a steel in-line fuel filter (no leaks/seepage). My only explanations are the vents for the reservoirs, and the unburned fuel/Air mixture in the manifold Evaporating into a rather small garage. Weather or not there should be ANY HC's escaping from the carb is the question.