I also had to try two chrome housings, the first one was a total fail before I rebuilt my engine. After I rebuilt my engine, I thought I could get the chrome one right and it did hold for about 800 miles then started leaking also. I dug out one of my stockers for my motor and planed the base for flatness and carefully reinstalled it and no more leak. I am using a 12# radiator cap. The only down side for me was I had the heat shrink hose clamps on all the hoses in my engine bay and now I have one SS screw clamp on the redone thermostat housing. At this point I am good with it, no leak:-)
