[Dave in Boise]

Interesting thread.. I am pretty hesitant to use 'vapor lock' as the cause for cars to stop running in warmer weather.. That is until our club took a 400 mile tour up and over mountains at 8700 ft in temperatures up to 110+ degrees ambient air at 5K ft. The top of the passes ran about 90-95 degrees at the top of 8-10 miles of 6+ % grade.. definitely a thorough workout for any model a, carrying people, spare parts and other touring items, up mountain passes in record-breaking heat.

I had seen cars that have never had an issue begin to fail at these temps and altitudes. Some were due to the excessive heat baking substandard or tired ignition components and having timing not properly set overheat motors and components to the point of failure. (abt. 60% in my estimation) One had a severe cooling failure as it boiled out nearly all of the coolant, and the driver did not pull over until the smoke started rolling off the engine due to the paint burning off and the oil smoking through the filler tube. Once cooled off, we fired it up and slowly added water to the radiator, checked ignition components and then retourqued the headgasket. the motor ran fine until it was shut down, and no vapor lock was noticed..

Most rolled along after setting timing and replacing ignition components with new parts. My personal car had issues with the coil (overheated so hot that I could not touch it and it swelled to the point that I had to take the clamp completely off the firewall to get it out of the clamp).

I did, though, actually encounter some vapor lock issues which I remedied by cracking the drain on my sidebowl and listening to the pressure hiss out until I got fuel flowing. Once flowing, the car started and performed well. I think the experiences we had were likely extreme, as we did hit 118 at one point, and we slowed our group down to 35mph and took our time in 3rd.

about 60% of our issues were ignition, 30% could be attributed to fuel boiling in the bowl of heat soaked carburetors (you could hear it and see the air rushing out of the line when cracked at the carb inlet) and some drivability issues due to carb jetting and other minor items making up for the last 10%

It was quite an experience.. We are still gathering up pictures from the tour and I will put out a thread on it soon fi anyone has interest in our collective insanity of taking these cars to the extremes we did.. 23 cars started, 23 finished (one on a trailer due to a suspected rear main failure we did not want to have the driver push his luck on)

- Dave in Boise