Hard Cranking When Hot

I bought the car in 94. It was in pieces when I got it.

I built the engine from the ground up. I have only put about 1500 miles on it in 10 years. (This car sits in the garage and collects a lot of dust.)

The battery has been in the trunk since I put the car together.
(The first battery ended up part way in the power steering pulley. The plastic mount that was used under the hood didn’t hold up to the header heat very well.)

The welding cables are very heavy. I made sure to get a large gauge wire for the CC AMPs they needed to carry. Much larger then your standard battery cables.

I have started to consider the fact that it may be a fuel vapor issue.
Heavy fuel vapor sitting in the cylinders/manifold maybe causing a compression issue? (I found an article about this, but not sure if that’s the case, and there was no reply as to if it helped.)

Someone suggested that when the engine is shut down the fuel in the carb is expanding from heat and running into the manifold. So setting the floats lower may help.

But it is instant in my case. I can shut the car down and instantly try to start it. I get the ½ crank and stop.