Vapor blasting will give the best result of all, almost over restored, but the finish will last for years and resist stains from oil and fuel. The cases will need to be lightly bead/sand blasted first as the vapor blasting process is not strong enough to remove heavy deposits like residual paint, carbon, old sealant and so on. The big down side is trying to mask off areas that you don't want any blast medium to get into. I have done this, but it is nearly impossible to mask off the timing side main bearings and more importantly the oil pump sleeve bore housing. There is a cavity inboard of the upper end of the pump sleeve and this area is impossible to clean, so if blast medium got in there, it might not be pretty...........So..........All engines I do now I remove near everything from the engine first, including all the bearings, oil pump sleeve, and the spindles unless they are in excellent condition, then you can mask them off to stop the ingress of grit. Two other areas of concern are the scavenge passageway, which if you remove the lower external grub screw removes that problem. The other is the cylinder hold down stud holes that pass through to the inside of the crankcases. These studs can be left in but remember to use lots of compressed air and blow vigorously up the holes to remove any grit. These principles should be followed as well if you are going to do the timing cover, all the passageways need to be opened up and thoroughly cleaned out first. I have removed covers off engines where the passageways were full of sand.................... Before you carry out any of this, the cases or whatever need to be thoroughly cleaned of any oil or grease deposits, especially up any holes or threads that have years of oil and crud in them. This is very important, probably most important because the grease and/or oil will act like a glue for the particles of sand/grit to stick to and can be very difficult to remove later. I use a can of brake clean or similar and blast it down all those holes, you end up with crap everywhere, but this is extremely important to get a great result. It is very time consuming, but the results are definitely worth it. Good luck with it all................
