1996 Civic Vtec engine Squeal

I installed a used Vtec engine in a 1996 Honda Civic, and to my surprise, the engine starts and runs pretty smooth. However, there is a loud squealing coming from someplace in the engine - it's hard to localize. I unscrewed the oil filler cap on the valve cover, and found that it seemed to be pressurized. As I released the pressure, the squealing stopped! If I remove the cap altogether, though, the engine began to run really rough. By the way, there is also a lot of white smoke coming from the exhaust. I checked the plugs, and it seems like they're wet with fuel (no coolant, so I think that the head gasket is OK). Any ideas?

Squealing is usually the belts. COuld be the timing belt. White smokeis anitfreeze. Head gaskets are very typicla on these.