Weird problem I can’t figure out

[Schmurda]

1977 c20 with a newer Gm good wrench 350 with about 13,000 miles and a Rochester quadrajet. Everything stock except for electric fans. I bought it last summer, stored it for the winter and pulled it out 2 weeks ago.

I have a new problem I didn’t have last year. After getting up to temp it wants to stall when idling. It never stumbles when I’m pressing the gas. I used stabil to store it, I siphoned some gas when I pulled it out of storage and  it looks and smells normal. Initially I thought it was a power issue so I replaced the battery and alternator. I also replaced spark plugs and wires. The plugs look fouled with dry black soot. Timing was set at 8, I advanced it to 13. I’ve tried tuning the carb but that didn’t fix the problem either.

I even tried seafoam in the gas but nothing has worked so far. Any ideas?

[bd]

It could have a saturated carburetor float or leaking fuel well plugs.  With the engine idling and air cleaner removed, look down the carburetor throat using a bright flashlight.  Does fuel dribble from the main nozzles?  Do you have to crank the engine for long before it starts when cold?

[Mike81K10]

Perhaps the carb, filter, and/or lines & Hoses got gummed up got gummed up. Fuel tanks were treated but those would not be unless you ran the treated gas through them. Change the fuel filter and try it out.

[Schmurda]

I ran it for a few miles with the treated gas before I stored it. I also replaced the fuel filter at the carburetor.

[frotosride]

Something to remember and always considered, ethanal is mixed at the pump. It will not and cannot bond with and grade of gasoline and will separate if given the time (winter storage) and more importantly any moisture at all.
If you keep this in mind and remember that ethanal is highly hygroscopic and no one can/has made a fuel stabilizer that can keep the ethanal and gasoline together because ethanol can't be stopped from absorbing moisture. When it breaks down the moisture and degraded fuel will settle to the bottom of the tank.

I'd place my money on that carb and fuel system needing love and anytime you store use non ethanol fuel.