Ding, ding, ding! The winners of this month's "Stump the Stovebolters Prize" go to 52Carl for telling me to remove the gas cap and check for a vacuum, and to Otto for telling me to check it for sure. I reserve the "Senior Moment Booby Prize" for myself for forgetting that I had replaced the ancient gas cap with a new, "improved" one sometime recently. I should know better than to trust my memory when sitting in front of the computer past my bedtime!
In all seriousness, I had replaced the cracked rubber gasket in another gas cap with a new one that I cut out of some thicker scrap rubber and it really was snug. Too snug! This is the smoking gun of a recent change to the fuel system that I had forgotten about. I have found this "vapor lock" thread to be very instructive. The awareness that Rochester carbs are already vented, that the engine quitting at peak demand is a result of fuel starvation rather than gas boiling in the carb, and that there is a high-quality new alternative to the stock gas tank are also important insights for me to remember. I will follow through with cleaning or replacing the gas tank this winter. I know that this 57 can run well at this altitude on this fuel.
Thank you everybody for your good advice!
1946 Chevy pickup, 1948 Chevy suburban, 1950 Chevy pickup, 1952 GMC pickup, 1957 Chevy pickup, 1939 Chevy pickup
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