My 400 in my 79 Bronco runs excellent but I am having problems with the fuel filter getting clogged up. It is a clear inline. I can drive it around and runs good put then I can pop the hood and after awhile I can watch the filter go empty. Filter has trash in it but don't look like enough to clog it. When I take it off and clean it I am ready to go again. Filter will stay completely full again for awhile. I blowed air into the line going to the tank with the fuel cap on, the gas that came back up the line was clean and clear. So I think my problem is the hard line coming form the pump to carb. When I check for fuel from this line the fuel is rusty colored. I also kinda thought about the idea that it might be vapor lockin but im not sure. I replaced fuel pump to make sure that wasent the problem.