Help! antifreeze in oil pan

[mdenno]

Anybody ever had this problem? Had engine (1972 454 LS-5) rebuilt and reassembled at a machine shop. Brought it home and installed in car and reconnected everything. Filled with antifreeze and oil and noticed oil dripping out of dipstick insert in oil pan. I figured that once I primed oil pump that oil would flow to remaining parts of the engine and level would drop below the dipstick insert. However when priming I noticed oil pressure gauge was not moving and the fluid was thin like water not oil. Drained out some fluid from oil pan and it has antifreeze in it. actually mostly antifreeze. I think the antifreeze got into the oil pan somehow during filling and the oil is floating on top of the antifreeze. The engine was not started. Any ideas how the antifreeze could end up in the oil pan:confused

 

[JohnZ]

About the only way that volume of coolant could get in the oil pan that soon without having run the engine (other than a major crack in the block) would be a bad intake manifold-to-cylinder head gasket seal/location allowing coolant to dribble into the lifter valley, then into the pan.

 

[minifridge1138]

I would agree with JohnZ (always a wise decision).
Most likely a bad gasket, intake or head.

Be glad you saw it before you started it.