Good morning,

Here is what I am discovering and again I do apologize for the lack of info. I have a 4 Barrell single pump Holly carb. I believe the heat is making a vapor lock as you stated. I am trying to solve that issue. I am in the process of getting a riser heat gasket with hopes that this will solve the issue.

Here are some question.
1.) Has the motor ever run right since it was built? / The motor runs fantastic until it gets hot. Since the day I built it. I did not go long distances many times, thus this issue does not occur a lot.
2.) Did it run better or the same with the Quadrajet? The Q Jet carb could not pump enough fuel into the motor and failed. Thus why I purchased the Holly.
3 .) If the engine ran good at some point what happened right before the issue started? / No it never did , i just did not notice or lock down the answer.
4.) Did the car sit for more then a year at any point? / no. only in the winter.

Thanks again guys. I will keep you posted on the results as I will be on vacation in 2 weeks and will swap out that gasket.