yea, i tihnk u use a 3/16th bit and drill on a 30 degree angle, then i tihnk a 5/16th bit for the other, i'm not building a serious street machine, as long as it works decently, its all good,i'm thinking with the cam i have, maybe the lift will make up for the small intake valve? or else maybe the compression these heads will make up for air flow? i would use a pair of 350 heads, but there arent any around for decent prices, its always usually smog heads with 76CC chambers, would like to maybe find a pair of closed chamber camel back heads, maybe i'll slap some on later on.