Cleaning a Clifford Valve Cover Question

If its shiny AL, I would consider soda blasting it. Sand will pock mark it obviously, and walnut shells might also pock it. Chemical strippers work but may discolor the AL, ie turn it black. I think thinner would be about the safest, maybe simple green? Dont use white vinegar, it will etch it. Whatever you use, test it on the inside first. hey, just ask our expert CudaChick!