Which part are you sanding now? Still the top where the cam covers go or the bottom that mates with the block. Please tell me it is not the bottom... You can have a shop skim them to clean them up (I did this on mine) or you can have them take off a little more to increase compression but first you (or the shop) needs to measure to see if it has been done before otherwise you can end up with clearance issues. I don't recall what the "safe" amount is to shave. I believe there are posts in the engine building forum about that.
oh, yeah, i'm sanding the head surface. and the block surface. it looks beautiful. but i did check it with a straight edge and it passed the .05mm test so i don't think i screwed up anything. and i spoke with people who've worked at car resto shops and they claim they would use everything from electric sanders to scotch brite pads so i don't think the surface is as fragile as everyone thinks.....
also, i've wondered if it's better to have a surface with cross hatching or a perfectly smooth surface and once again, no one seems to be able to answer that. but i think i know why: it doesn't matter. i've seen both smooth & crosshatched so maybe that doesn['t really make any difference.
oh, well, talk is cheap. won't really know til i bolt this junk together. i'm getting fed up with it so i think i might just throw it together and see what happens. it's only labor which i've got in spades right now. so if my cheap head gaskets hold, then great. if they don't then what have i lost? a few weeks of pulling my engine apart again and an important lesson learned.
just friggin tired of sweating the little stuff. these engines respond to emotion, not whether a surface is perfectly flat or not. bolt it up and rev the hell out of it and see what the hell happens! that's my new motto.
(hopefully i won't live to regret any of this....)
and as far as compression, how much do you need to take off to increase compression acceptably? what's the formula for this? how do you know? i don't think the alfa heads have much that can be removed so maybe that is why you never hear of anyone doing this. i swear in close to 10 years on this board i don't ever remember seeing anyone decking the heads to raise compression--what gives?
oh, yeah, and stay tuned. as if you didn't think i was dumb enough, i'm also going to port the heads and maybe try a 3 angle valve job. i have some good info on the porting and also about a 70* valve seat cut to effectively increase the valve area by 2mm. i tried a little smoothing with my dremel to see how tough aluminum is and if you really need a host of carbide grinders. my dremel cut right through it! yup, aluminum is **** soft. anyways, still need to buy the Neway valve seat cutters (which is a litle bit of an investment) and some long shaft grinders and some calipers for proper measurements and then, voila, i'm off to the magical land of freeflowing heads and free HP and 7000rpm fast revving alfa engines.