Another small block turbo early valiant

I have run the MSD 6AL on everything. I love them but on my recent turbo build I am using the Holley distributorless ignition. So far I love it especially not having to deal with the plug wires on the distributor. If you the mopar ignition then you’ll have to close the gap on the plugs to keep them from not sparking under pressure.
Why do you have the close he gap on the plugs, and how much?