ls/vtec oil tap?

Can anyone explain to me why I would need to tap a b16a head to work for an ls/vtec setup? Why did it not need to be tapped when it was on the b16a block? Does it have something to do with the block supplying the oil and not on the non vtec block?

help me out here.

i could be wrong here, but i think you tap the block and then run a line from it to the head, i think the head already has the tap since it is natively has vtec. i think you need send and return lines but i am not sure......

I have read several times though, that you have to tap the head...

It's because the VTEC B-Series blocks supply extra oil to the head internally. That's the hole you have to plug. The non-VTEC blocks don't do that, so you have to run an external line and tap the head.