I was just wondering...is it possible to have the combustion chambers opened up on a set of heads to give you more cc's and decrease the CR? Like say you have a set of heads with 200cc runners and a 64cc chember on your 350 and you wanna go to a 383, but it will be like 11:1 with that chamber size, could you have the chambers opened up any way to drop that down?? i know i could switch pistons etc but the 383 im looking at already has forged flattops and i dont wanna have to buy new ones. again, just was wodnering.

Yes, taking out metal will drop the compression ratio.

any ideas on how much can safely be removed and if it will ruin the flow at all?

If you do it right, you can gain flow.

Pretend you're deshrouding the valves. Remove material between the intake valve and spark plug boss. Smooth the spark plug boss. Remove material between the valve and chamber wall (both valves.) etc etc. No such thing as "perfectly non shrouded", you can always do better

My 416 heads had 58cc chambers stock, and i'm now at 64cc. It wasn't a lot of metal, truth be told. I wouldn't have a problem removing a fair bit more. But this is a moderately thick factory casting, an aftermarket one might be considerably thinner, and already have those areas removed. ie, no material left to open up in those "helpful to flow" areas.