engine help!

look for vacuum leaks, the rubber vacuum lines and plastic connecters get old and break causing them to leak, this will make it imposable to tune the engine properly,
you also want to check for old or dirty fuel, water in the fuel, clogged fuel filter, dirty air filter, fouled spark plugs, old bad spark plug wires, corrosion under the distributor cap, stuck or non operational choke, dirty carburetor, timing out of adjustment, dirty points (if it is not electronic ignition)