Keep an eye on you anti-freeze, mine did the same thing when cold, when I'd start her up, there would be a good amount of white smoke,t yes indeed, the old HG started to leak after 297,000+ miles, I didn't want to believe it, but it was so. I since rebuilt her, stronger than ever now!
What happens is, coolant leaks down into ye olde cylinder and you start her up, she will smoke for awhile and once the engine warms up, the HG leak will seal itself due to the heat expansion!
Good luck, I hope it isn't the HG! They're fun though!

* Harry * <img src="/forums/images/graemlins/cheers.gif" alt="" />