I have been having severe vapor lock on my '79 corvette the past few summers. I've been driving the car for around 30 years with no issues before now. It seems the ethanol content is causing the fuel to vaporize at a lower temp than the car is built to handle. The problem happens as soon as the car is shut off and is allowed to sit for a few minutes. Winter gas (spring driving) (lower vaporization point) and Calgary's altitude don't help. The car is now completely unreliable. I will have to switch to fuel injection to have any sort of reliability.