Hi Paul: Your question is an interesting one. I'm assuming you'll be power washing the compartment for best results. The way I've always done it is to cover the cridicial parts with plastic "baggies" & use rubber bands for a tight fit. I'd definately cover the distributor, coil & the air horn of the carb. As for the spark plug wires, don't worry about them getting wet. They're designed to get wet & if they're bad, getting 'em real wet will be a real good way to see if they are bad. As for the starter. No worries about getting that wet also. But don't concentrate on it too much unless it's really dirty & greasy. Same goes for the Alternator (cover that if possible). Also, if your using a aftermarket degreaser, such as "GUNK", be prepared to remove some of the original engine paints, as this sometimes happens. If you degrease while the motor's warm, it'll do a better job. Let the degraeser work (as the motor cools down) & don't spray the engine if it's "Hot": You could risk the possiblity of cracking things as the cooler water, when hitting hotter parts could do damage. After you wash the compartment, dry off as much of the electrical stuff as possible, wires & such. Remove the plastic around the carb, disttributor & coil & make sure they are dry. Then start the car & if it runs ruff, just let it run & it should smooth out. After a good cleaning, you'll now be ready to do some serious detailing. Good Luck!
Dave