Chevy Tri Five Forum banner
1 - 13 of 13 Posts

·
Registered
1957 Chevy Bel Air
Joined
·
4 Posts
Discussion Starter · #1 ·
New to the forum.

I have an original 57 bel air with the 283. The carb is directing fuel to the vacuum advance. Usually to start the car, I have to prime the carburetor by taking off the breather and splashing some gas directly into the carb.My family has done this for decades to this car to start it (the thought being less wear on the starter). So now when I pour gas into the carb the gas leaks out of the vacuum advance on the distributor. I have no idea why this has just started. I’m assuming it is a carb issue, but I’m not sure.
Full disclosure: I’m new to this mechanic thing so if you could dumb it down for me that’d be helpful. Thanks!
 

·
Registered
Joined
·
2,036 Posts
Dumping gasoline in the carburetor is a bad practice. It not only washes any protective oil from the cylinder walls but if you dump in too much you could hydrolock a cylinder and cause major engine damage. If the car has been setting for a while just keep cranking and it will eventually start. If you want to speed up the process fill a squirt bottle that can deliver a fine stream of gas and use it to add a small amount to the float bowl through the vent tube.
 

·
Trifive Automotive Electrical Wiring Expert
Joined
·
27,084 Posts
The distributor vacuum advance is a closed system. If gas is leaking out, the vacuum pot on the distributor is bad and leaking or the hose is leaking.
Dumping gas in the carb is also very dangerous and can cause a fire.
 

·
Registered
Joined
·
1,355 Posts
I don't believe I have ever heard of anybody doing that to lessen wear on the starter. A starter is a lot less expensive than a fire.
 

·
Registered
1957 Chevy Bel Air
Joined
·
4 Posts
Discussion Starter · #5 ·
The distributor vacuum advance is a closed system. If gas is leaking out, the vacuum pot on the distributor is bad and leaking or the hose is leaking.
Dumping gas in the carb is also very dangerous and can cause a fire.
Ok so, I understand splashing gas in the carb is a no-no now.

So you think it could be a bad vacuum advance unit and not something wrong with the carb itself?
Could it possibly be from pouring gas directly into the carb? I never felt super great about doing that, but it’s just bad habits passed down I guess.
 

·
Registered
56 150 two door w/210 trim, 350 CID, TH 350
Joined
·
653 Posts
Another slight positive about cranking longer on start-up, is the delayed start allows the oil pump to force oil everywhere before cylinder pressure jumps up, potentially saving wear and tear on the lower end and cam surfaces.

Just a thought.
 

·
Registered
Joined
·
873 Posts
You've been doing it for decades and haven't burned it to the ground, I doubt if you will now. I will recommend one thing, I take one of the 20oz Coke bottles, wash it out good and drill (4) 1/16" holes in a line into the cap. This lets me sprinkle a little bit of gas into the carb without worrying about getting too much in it. As to the vacuum issue, I would disconnect the vacuum line at the carb and put in a splash of fuel as you normally do and see what happens - my guess is that the fuel will leak out of the fitting. From there you would have to pull the carb and go through it to see what the problem really is. Since you're new to this stuff, you probably should find someone that has some background in working on carbs. As to the oil/cranking issue - I have pulled apart my share of engines in 50+ years now and every single one of them whether it has been sitting for a day or 10 years has had some amount of oil on the rod and crank bearings.
 

·
Registered
56 150 two door w/210 trim, 350 CID, TH 350
Joined
·
653 Posts
Yep, oil is by design supposed to hang around on metal surfaces, I was only stating the oil thing as a bright side for excessive cranking!
 

·
Trifive Automotive Electrical Wiring Expert
Joined
·
27,084 Posts
. As to the vacuum issue, I would disconnect the vacuum line at the carb and put in a splash of fuel as you normally do and see what happens - my guess is that the fuel will leak out of the fitting. From there you would have to pull the carb and go through it to see what the problem really is.
The port on the carb, that the vacuum advance connects, is an open hole into the throat of the carb. There is nothing wrong with the carb. The leak is in the vacuum advance pot or hose.
 

·
Registered
Joined
·
873 Posts
The port on the carb, that the vacuum advance connects, is an open hole into the throat of the carb. There is nothing wrong with the carb. The leak is in the vacuum advance pot or hose.
It appears to me in pictures of original '57 283 engines, that the vacuum line is connected to the base plate of the carb, not the throat. So the question to me is how is a splash of gas getting into that line when it should be simply running past the throttle plates and into the manifold plenum. And it is not normal to have ANY fuel in the vacuum line to start with so I fail to see how the vacuum pot on the distributor is the culprit other than the fact that it was never designed to hold fuel.
 

·
Registered
1957 Chevy Bel Air
Joined
·
4 Posts
Discussion Starter · #12 ·
Also I should mention that I have had engine roughness on initial throttle input. Then it smooths out.
 

·
Trifive Automotive Electrical Wiring Expert
Joined
·
27,084 Posts
The diaphram in the vacuum advance pot is leaking, keeping the distributor from advancing and letting the fuel to run out.
 
1 - 13 of 13 Posts
Top