the engine is a stock 305 from 76, it was running good the last time it was started, the thing is that was almost 3 months ago, when i started it he started good but at 15 seconds of being started i noticed the alternator smoking and turned it off, then i tried again to start the engine and after a short while it died.
when i start it he seems normal, then after a few seconds looses power and dies, even while pressing the gas he still loose power.
what is the reason for this, could this be a non working fuel pump, or a defective carb when i press the accelerator it sounds like there is vacuum.

The smoking alternator doesn't sound good.
Pull the alternator and have it tested.
It may be drawing your voltage down so low (internal short?) your ignition isn't working right.

The smoking alternator doesn't sound good.
Pull the alternator and have it tested.
It may be drawing your voltage down so low (internal short?) your ignition isn't working right.
how do i know about the ignition not working right??

The alternator powers the entire ignition system. Without it, your battery fires everything, and will wear it out quickly.

Just remove it and take it to a parts store or someplace that rebuilds them and get it tested. Prolly takes like 15 min or so to test.

The alternator provides about 13.8 volts and lots of amps at above 1500 RPM, which is essential for ignition system at that speed...

tried to car the engine today again, it started almost imediately, but at the beguining i had to be pedling the accelerator for the engine to keep runing, after a while he idled alone by itself, but still when i press the gas it seems to get flooded, after i turned it off the engine bay had a strong gasoline smell, i think the spark plugs wires may be a little loose im going to check them when i have sunlight.

First of all, if ANY component is smoking on your car, REPLACE IT. That is how fires are started.

http://www.napaonline.com/masterpages/NOLMaster.aspx?PageId=470&LineCode=RAY&PartNumber=2134011&Description=Alternator+-+Remfd+-+Standard

replace it/

Everything you've said screams alternator. Its smoking.

It should be, as noted, charging at the 13.8V or within .2 of that. Does the car have a guage or trouble light....it should have something. An Alt light should at least be on.

As you kill the battery it should turn over slower when you try to start and eventually it won't start. Then you pretty much have no choice but to try the Alt. You at least need to dsicount it as the obvious likely problem before looking for other culprits.

doesnt your car have an volt gauge mine does and its a 78 so if your to lazy to test the alternator look at the gauge if it isnt more volts after starting then you got a bad alternator. But about it dying, do you have a cat? cause when cats meltdown you cant rev the engine cause of exhaust pressure build up.