The sears craftsman engine analyzer, is one of the best you can afford, at the store it sells for $49.99

not including tax.  It ranges in helping you distinguish some engine problems from electrical-starter and alternator, to helping you set the rpm's on your engine.  A great back up tool to the timing light.

Also helps in tach and dwell for older vehicles that still have points and condenser, whereas you would manually set these items with feeler guages.  The storage box on the back side can be removed, if needed, to account for a smaller unit, but, I myself prefer to keep the unit in tact and keep the storage box on there to hold the extra cables.

For the money, this is a great add-on for the home mechanic, who prefers to have his vehicle with an original carburetor.  You can still use it, for some fuel injected model of vehicles..