Wont Start when warmed up

Hey this is for a buddy of mine with a 79 jeep with a 351 in it, it will start right up and drive fine, but when you shut it off, it will not start back up, the motor turns over fine but I don't know what the deal is it won't start, after setting for about 20 minutes it will fire back up, not a real big problem right now, he is just worried about getting in the middle of a mud hole and stalling and having to sit there LOL...that would not be fun.....any help would be greatly appriciated

Sounds like a possible fuel vapor lock problem. Check the fuel line routing and make sure the line is not contacting the intake manifold, engine, or laying close to the exhaust.