18. The last portion of the tunnel that needs to be made is the recess that houses the distributor. SKS chose to leave the area small, compact, and neat. For that reason the area is shaped in the vein of a bell, but it will need to recess several inches into the firewall to clear the HEI distributor. A template is made to the shape of the opening, and then an extra 3 inches is added to the outer edge.