Exhaust Smoke at exhaust manifold port

[AWC123]

I have a 1964.5 Mustang with a V8 260. Today I noticed white smoke at the exhaust manifold port (driver side) closet to the firewall approximately 2 minutes after crank while at idle. The smoke is continuous at idle, but pretty minor at this point. If i rev the engine the smoke continues it just streams with the airflow toward the rear of the car. The smoke appears white.

A closer inspection of the exhaust manifold revealed a cracked flange at one of the manifold bolts. The cracked flange is on the front side of the port, the smoke appears to be from the rear side of the port toward the firewall. My manifold does have a gasket. I tightened the bolts on the leaking port slightly but no change. There is no smoke out of the either tail pipe. I assume the cracked flange is not recent as I have done no work to the manifold. I have driven the car for the past few weeks and no smoke so its hard to think the cracked flange is the issue.

I have recently conducted a tune-up (thermostat, radiator flush, fuel filter, pump, belts, and timing) I changed out the spark plugs also and discovered oil and crude on a few of the plugs. Also The exhaust pops on downshift and at idle (not constant) but on downshift or to be more specific when I take my foot off the pedal and let it coast while still in gear.

Where should I start? It is an easy fix to think it is the gasket at the manifold, but why would there be smoke anyway. Any help would be appreciated. Thanks

 

[horse sence]

white smoke could be anti freeze. does it have any particular smell/burning oil or sweet smell form antifreeze? back fire is probably from the cracked manifold .
pull the sparkplug for the exhaust port that is cracked and inspect ,check for oil or antifreeze.

 

[PoppyMod]

Hi,
+1 for the coolant leak. White smoke is a classic indication of coolant in the combustion process. It's quite possible, the crack there is the first place for the smoke is entering the atmosphere and not significant enough by the time the exh. exits the tailpipe. Too, it's probably a minor leak at this point. You should prepare for a head check and a gasket replace, not to mention repairing the exh. manifold. Looks like a winter project to me.
Good Luck