Are they the red blocks? Do they have 3 or 4 emulsion holes? Also what blocks are you replacing? Stock Holley?

The blocks do have fixed emulsion holes and you should not need to adjust anything emulsion wise. What you will most likely want to do is increase jet size maybe 2 -3 steps rich when replacing and tune from there. With more emulsion more air in the mixture. (This is if you are going from stock holley blocks that have 2 fixed emulsion holes.)