I haven't driven my 75 in about 3-4 years, it has almost a full tank of gas. should I siphon all of the gas out, I get conflicting advice.

Thanks,
Rod

If it was me...I'd siphon it all out. Probably take the fuel line loose on each end and blow that out also. I wouldn't risk running that old gas through my engine. But that's just me.

I would drain the tank.  No telling what sea creatures have taken up residents in your tank in the past three years !! dskopp2009-08-24 15:20:02

It's 6 one way, 1/2 dozen the other...
I've had cars sit for longer than that with full tanks, and never drained the fuel to start them up. The '85 has sit a couple of times for that long, with no problems when it was time to fire it back up, although a fuel filter change was warranted. My 'Burban sat for 4 years without starting at all...fired right up when I got ready to drive it again.
Really depends on the quality of the fuel to start with, the condition of the tank, and the environment...where does the car sit? Outside? In? Hot weather? Freezing cold? Humid? Dry? ALL of the above? Was there any fuel stabilizer put in it before it was stored?
Take the cap off and smell the fuel. If it don't smell like gasoline, it might be best to drain/refill. If it still smells like gasoline, I'd say fire that puppy up, and go for a ride!
If you're that concerned, drain it, and use that fuel for your lawn mower/tractor, so it won't be a total waste.

I had mine in much longer than that, I just topped off the tank and garaged it. It started and ran fine. Do like Joel says and sniff it.......

I'd change the fuel filter and crank the motor of a few seconds and let her pump a little fuel into a jar from the fuel line going into the carb. The fuel sitting in the tank is in far better shape than what's sitting in the lines. Crack the carb linkage and see if fuel is squirting into the manifold to make sure your carb isn't varnished up from old fuel sitting. Also, check all your rubber fuel lines before doing anything farther than a trip to the 7-11 and back. LukesVette2009-08-25 05:22:19

Thanks everyone for your help, I have decided to empty the tank and start off with fresh gas. Better safe than sorry, I have a new fuel filter (I also ordered a new set of rubber hoses). I'm towards the end of rebuilding the brake cylinders, so doing one more job won't hurt.

Rod

I would definitely drain the tank and also flush the lines

Was the tank full full all the way to the filler opening or 3/4 full. what happened to me was I kept getting rust sediment at the bottom of the tank, Idrained the tank and flushed it and it would be clean for a while but the sediment would return, the bottom and sides looked good accept for the seditment, I took a teliscoping shop mirror and with a flash lite  pointed it towards the up side of the tank and found rust had eaten through the protective galvanizing and it was rusting through, what happens if the tank is not kept really full and the car sits is moisture builds up in the tank and hangs from the top of the tank and rots it if not drive now and then... anips2009-08-26 16:43:23

When I got a flash light and took a closer look inside the tank, I saw that it was not full. I siphoned out about 7 gals of old gas. The inside of the tank looked very good, no rust sediment that I could see. I actually think the old gas was in pretty good shape, it didn't smell foul and wasn't discolored. My garage isn't heated, but it is attached to the house and fully insulated and doesn't get humid at all. I changed the fuel filter, inspected the rubber fuel hoses (they looked good also, so I didn't replace them), put a fresh batch of gas in the tank and cranked her up. Of course I flooded the carb because I didn't change the old battery (I had it connected to a jump starter, so I thought it was fully charged) when I turned the engine over too many times . I let her sit while I bought/installed a new battery and she fired up right away.

Rod