I’ve done a few aircraft & car degreasings of aluminum
block engines & have tried most of the off the shelf products. If the grime
is not to thick or for the final cleaning stages, I would recommend “engine
brite” gel by gunk, let it soak in for about a half hour then you can hit it
with a power washer / pressure washer (with just water) or just a hose. Almost all
the general auto stores & walmarts sell gunk brand. I have not read or
encountered adverse reactions with aluminum with this product. The main thing
to watch out for is electrical items are protected from cleaning chemicals and
water spray.
The 2 common cleaners to avoid on Aluminum is Chlorine
(bleach) and oxy clean!
I’m using a Corvair engine on my project, when I got the
core it was coated in a thick oily sludge, I scraped off all the thick stuff
with wood & plastic scrapers, then went after it with a brush then I tried all
the degreasers, simple green, soaps and even carb cleaner to get off the sludge
in the end I found the gunk gel the best performing followed up by a pressure
washing.
Here is some product info
http://www.rscbrands.com/products/prodinfo/EBGEL.PDF
http://www.rscbrands.com/products/product_images/VL_EBGEL.jpg
Hope this helps
Spencer
EAA Technical Counselor (composites / powerplant) TC # 5426