He are some general tips that may help,
Idle quality does not effect driving quality. Once the throttle is opened, even a little bit, the carb switches from idle circuit to drive circuit. Full throttle is also different. So you can have one with out the other. I would start with a carb rebuild if you already haven't done it. These are very simple to rebuild. They need to be super clean and have clean fresh fuel. So clean it again if it still acts funny.
Modern fuel goes bad a lot faster then old fuel used to. Don't store it to long!
Valve adjustment usually will not effect driving much unless its way off. If all the rocker arms sound about the same, then the adjustment is probably pretty close. If you hear one clatter more then the others, its time to read up on valve adjustment. Its a good idea to check them and set them once you know how. Being to tight will hold a valve open, you will hear a "pop" either in the carb or tail pipe, depends on which valve is held open. To loose and you can hear them clatter much louder then normal. Dirty oil will muffle them some.
Timing, vacuum advance, points gap, plug wires, and spark plugs, all should be checked as they will effect drive more then anything thing else. Vacuum advance should be working and can be checked really easy, just watch the distributor house for rotation as you rev the engine and let off. Throw in some new plugs if there is any question about them, same with wires and cap. File the points and set the gap. Setting time will easy with a light, its nothing different then what you are used to.
Read your manual or check out this one,
http://chevy.oldcarmanualproject.com/engine/56etu/index.htmPlug all but the vacuum advance line including PVC if it has one. Install a vacuum gauge at the manifold or below the throttle blade. Above throttle blades is what is know as ported vacuum ( only has vacuum when the throttle is open). You want full time vacuum, I would expect you to see 18 to 20 inches at idle, possibly more. This is where valve adjustment will be seen. Smooth steady needle, great, jumping around or low vacuum, valves timing is late. As the clearance in the rocker arm to valve stem gets looser, the valve opens less and at a later time then designed for. The cam is always turning, as it turns it pushes the valve open, if the gap is to big, you loose a large number of degrees of rotation before the valve opens. In effect, a large valve stem gap makes the cam smaller in both valve lift and the amount of duration the valves are open. The valves also close sooner causing even less duration.
Using the vacuum gauge while setting the timing helps, try to set for the maximum vacuum, still able to crank easy, and not ping under a heavy load (pulling a hill in high gear). Its a little trial and error. Todays fuel are still better then they used to be so you can get by with more timing then the manuals call for, more is better then less, just don't go to far. As long as it fires right up without trying to kick back, you will be good to go. Again, read the manual I posted above, 4 degrees at idle is not much, bump it up to 6 or even 8 and see how it runs. More timing helps keep the engine cooler.
Joe
