When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Not sure of the best way--after a v10 and on my 2nd 6.0--first, just hose it off to get rid of the dust that accumulates. Don't let any dirt build up. Don't wash it while HOT.
Don't wash it with high pressure. Several guys I know spray it with Simple Green and hose it off. At least we don't have to worry about wet spark plugs.
On a slightly warm engine, I hose it off with the nozzle removed from the garden hose. Then I spray it down with an entire bottle of the cheapest "citrus" cleaner I can find. Wait five minutes and then rinse again with low pressure water flow.
Keep liquids out of the alternator. Fire it up and run it afterwards to get it hot and dry everything out. I do this twice a year and have never had any problems.