Ka-pow!

"Back in the day" my Harley and my 72 duster let out a big ka-pow when they started- LOVED IT!
Like you said only when cold and no other problems. It was a stock 80k 318 I put a 340 size cam, headers, and a holley 600. It would run perfect on the highest octane, but if I put anything less than the highest octane it would run as if it was only hitting on 5 cylinders.