I had a clearance issue on my Merc build where the fill cap was hitting the hood. There was no way to recess the radiator so I had to cap off the radiator side tank and installed an inline fill tube in the upper hose I bought from Speedway. The problem is there was about 2.5 to 3 inches of air left in the top of the radiator and the coolant would steam up and expand only to push coolant out the catch can. I had to do something to get coolant to the top of the rad. I looked at a bunch of options, even bought a cool brass expansion tank for a Nash, but everthing had inlets and outlets in the wrong places. Sooooo, to build my own!!! Ride along and hope this helps someone else!! Here are a few pics of what I started with. Slightly modified SUMMITT radiator and Speedway inline fill tube. This setup just didnt cut it!!!