Ideas Invited- smoke only upon startup

["R. Cobb" <rcobb@earthlink.net>]

My BJ8 runs well under all conditions.  It has about 2500 miles on a 
professional rebuild of the engine and carbs.

I notice that if the car is parked for more than 5-10 minutes, upon 
restarting, there is a small ball of smoke that comes briefly from the 
tailpipes.

Addressing this phenomenon solo, I haven't been able to be at the 
tailpipe at startup to smell the exhaust for oil or gas fumes.  Any 
suggestions or thoughts as to diagnostics or corrections?

Thanks in advance.
R. Cobb