Re: \'85 Still getting horrible gas milage
If your 85 has the stock Holley 4v, it should be as easy to rebuild as any other Holley, with good results. Sounds like you may have the power valve stuck open or leaking, or some other little internal leak. Should be fairly easy to fix. My 82 with a total aftermarket Holley does this every now and again. It turns out that the gasket between the rear jet plate and the rear of the carb body gets saturated and leaks, dripping fuel into the secondary idle passages all the time. If left long enough, it will slow the idle down and pour black smoke at idle. A new gasket fixes it. Holley says the parts warp over time and will do this. I just fix it every year or so. \
At 266k miles, I would also be looking at things like the timing chain being stretched, and perhaps having jumped a tooth or so. Or the valves getting worn and not sealing real well. Check the cam timing and ignition timing to make sure they are ok.
You really do need to do a compression test. Hard starting is also a sign of tired compression.
You could also be having an ignition problem. If that is suspected, just change it all, it's inexpensive stuff. Start with the coil, the plug wires, the module, and then the dist pickup coil. If the coil or dist pick up get tired or fail in cold or hot modes, they will cause intermittant poor running, and usually, sometime, a not running situation.