Possible water pump issue, lack of flow at idle. Did you use the same pulleys or aftermarket?
Possible head gasket issue or even timing problem, cam and distributor should be verified. And don't forget to verify the timing mark at the dampener. Sometimes zero isn't zero, needs verification.

It sounds like you either have a lean condition due to a carb setting being wrong or the timing is wrong and the combustion cycle hasn't completed but it's being pushed out the head.