RaZ wrote:
what kind of crazy grinder/grinding wheel are you using?
I've got a collection of stuff that I use for this crazyness. The main weapon is a bunch of 4" flap wheels starting at 60 grit and going to 120. Don't buy the cheap plastic back ones as they explode and leave nasty bruises (I can still feel that one - worse than a slap shot to the gut).
Everything get's roughed in with the flap wheel, then the difficult areas are blended in with a carbide burr on a die grinder. I then switch to tapered or straight sanding rolls (Eastwood) from 60 to 120 grit. If things are being painted, that's far enough, if they are getting plated, then I continue to 320 (my ceramic coated dual down manifold was shiny before I had it plated). Get a real die grinder (hell mine's from that famed Power Fist line of quality tools - both air and electric) doing this with a Dremel is too damn slow.
There's a lot of touch involved with doing cast iron, a little too much pressure and the 60 grit wheel can make a mess pretty quickly. I take my time and do lots of thinking along the way about whats inside the casting, where more material can be removed and not comprimise strength etc. Blocks are tricky because they are thin in areas and you sure wouldn't want to cut into an oil or water passage. Generally remove the casting sand impressions and you're OK.
So far the engine, transmission, rear end, manifolds, and rear brakes have all been done. The best part is that you end up with crazy rust stains on your shirts.