So the wife is borrowing a power washer
 

She wasn't to wash the house. I was thinking of power washing the engine. for an 86 LG4 (4BBL) is there anything I should cover up so I don't f-up the engine? I'm thinking at a minimum battery and alternator.

batt, alt, carb, and it woudl be a good idea to pull the plug wires off and make sure the plugs are all in tight.
make sure the engine is cold too, a little cold water on warm metal can break stuff.
make sure the alt is sealed at the bottom against the intake too.

i think most powerwashers superheat the water dont they?

no it depends on if its a steam washer or a regular power washer

I think this is just a regular one. I figure while I have it I might as well try it.

No, only steam cleaners heat the water.

Don't do it. Keep power washers away form the car. Take it to the self wash and use theirs. It aint so powerful. You'd be surprised what a bottle of Castrol Super Clean can do.

I need to wash my engine... it's prolly got 20 lbs of dirt and grime on it right tim?

Use engine de-greaser and a regular hose and watch your electronics. Power washing an engine is a bad idea, especially the old Carb'd ones with the plastic vacuum lines. Steam clean it or de-grease it but don't pressure wash it. Also Simple Green works very well at getting grease and oil off. Just be patient and do it a bit at a time.