I had a '78 Accord which had a pin hole leak in the water jacket in the intake manifold. This leak produced white smoke and over a period of time it eventually caused the head gasket to fail. Upon removing the intake manifold, there was a distinct line of dried up white antifreeze residue running down the inside of one of the intake runners. Pressure testing the manifold's water jacket with compressed air in a sink of water confirmed the leak, air bubbles came out through aluminum runner.
Eric