Engine cleaning

I’m renovating a 1972 450, which unfortunately has a patchy dark discolouration on the rough-cast engine casings. I’ve tried numerous aluminium cleaners without sucess - any suggestions??
Martin (7137)

I have heard some people have good results with CillitBang oven cleaner.

Another option may be a steam cleaner - I have a domestic unit (hard wood floors) that I use to good effect on greasy engine parts. It has a tiny nozzle designed for the grout joint on wall tiles with a little brass brush.

Sounds like the porous castings may have absorbed the contamination though if alloy cleaners (which are mildly acidic) haven’t managed to shift it.

Some specialist cleaning companys will attempt vapour blasting with media such as walnut shells with the engine not stripped. That may be an option.

Hope thats helpful.