What causes a Chevy 350 1977 camaro fresh rebuild that blows water out exhaust?

Is it water or antifreeze ???

It is probley condensation. If it is cold outside were your at then this is what happens. The exhaust system is cold and when you start the engine the exhaust

heat flowing through the cold exhaust pipes makes the exhaust sweat. And it

looks like water is running out. Engine is running lean. Needs richen up.

If it is antifreeze it will be smoking real white out of the exhaust. And that would

mean a head gasket is leaking coolant into the piston cylinder. That is the most

common problem with a antifreeze leak causing white smoke.

I have seen intake manifolds leak coolant into the cylinder head ( runner ) but it

is rare that happens. I don't think you have a problem.