As with panels and body damage, you must keep in mind that your car's internal machinery is both a useful part -- it makes the car go -- and a classic piece of engineering in its own right. For many of us, engine reconstruction and repair is the main draw. There's nothing quite like the feeling of reconnecting everything, double-checking spark plugs and fuel lines, then turning that key.
However, it's important to keep in mind that the engine itself is a very complicated and efficiently designed collection of steel. Damage that's difficult -- sometimes even impossible -- to see can make the difference between a champion driving machine and a yard ornament -- or worse, a safety hazard.
Make very sure your engine block is undamaged, all the parts are in working order, you've replaced every tiny part that needs replacing, and it's not leaking or dripping anywhere. The engine is one of the main focus points of any reconstruction, but because it's the most complex, it's also the easiest to get wrong. Most of us imagine ourselves buffing the new paint job or waxing our "baby" on the weekends -- but truly tending to your vehicle's needs and making sure it's kept up means treating that engine like a princess.