Porting BB heads

I used to think I was porting heads spending hours wirh a high speed grinder and flapper wheel then I had the oppertunity to put them on a flow bench only to find the flow in some instances went down If you don't have a flow bench you can't port heads. you can remove poor casting iron from the ports without hurting the flow and it might help but don't fool yourselph into beleaving heads can be ported without a bench.