worst case scenario for me when this happened with the 429 engine in my t-bird was that the rings were bad, expanding in the cylinder, then labored starting, then when it cooled off it started.
Fairly uncommon issue, highly unlikely it is this!
JOE
1983 F150 XL Flareside, Shortbed.
4 X 4, auto, 351w, 4bbl added.
"It's hip to be square."