When I wash my engine I cover the alternator and the coil packs with plastic bags. If you have an exposed intake cover that too.
Pressure washing isn't necessary unless your engine is terrible. I usually spray the degreaser, let it sit, work it in with a brush and rinse with low pressure water so nothing gets knocked loose.
I barely even do that though, the engine has gotten washed as often as the outside of the car since day 1 so it's pretty much spotless.
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1998 Pontiac Grand Prix GT
WizAired CAI, Impala 12" Brake Upgrade, ZZP Alternator Rewire and Voltage Booster, Rotated Dogbone Mounts, Kicker KS690 6x9s, JBL GTO427 4s, JBL P652S 6.5s
2001 Ford F150 XLT SuperCab
Stock, LineX, 212K