Since this setup has been working reliably for a while, and you encountered problems only recently, I am guessing that the responses so far are probably much closer to the real root-cause. However, I will share my experience with this problem since no one has mentioned this as the possible culprit so far.

Small block, mechanical fuel pump, carb bowl vent line to the charcoal can and vapour return line to the tank, Carter TQ (9800 series) carb. I had meticulously set up the carb prior to getting this thing on the engine. Point being: bowl vent was functional, etc., etc.

Well, as I got the car running and kept on adjusting things eventually that caused my fuel bowl vent the get out of whack, result being: car was a bear to start as soon as I would have it sitting for as little as 10-15 mins.

At first I thought maybe it was just my fast ignition curve with about 23 deg. initial timing, but the starter wasn't fighting me...so what's next? Well, I went back to the basics, re-checked things and sure enough found out that my bowl wasn't venting anymore. Fixed that (super easy on the TQ), and went back to enjoying the car.

No heat wrapping anywhere, just a 3/8" fuel line feeding "da beast" lol