High all and happy holidays. I have a quick question. Anybody have trouble with radiator leaking at start up? When I first start the 51 up (1951 1/2 ton Chevy with original 216)as it warms up before the thermostat opens,it pushes anti-freeze out the overflow. I have a 0 lbs. cap on the radiator now. I tried a 4 lbs. cap before I got the new one (0 lbs.)and I would get a leak on the drivers side of the block until the engine warmed up. After the engine warmed up it wouldn't leak any more. The engine was rebuilt by previous owner but was nerer started. Everything is alright after the first time the thermostat opens, no more leaks.Any sugestions on what is hapening here? Thanks in advance.