Re: stalls when hot
Don't know what to tell you about your schedule. But on vapor lock, squeezing the bulb till firm might allow you to get by.
Liquids boil at lower temperatures when the atmospheric pressure is reduced. The fuel is in the tank. The fuel pump is a diaphragm pump that sucks on the fuel line bringing up the fuel. When the volatile fuel is sucked on by the fuel pump there is a reduction in atmospheric pressure caused by the height the pump has to suck the fuel and any restrictions in the line...fittings, the squeeze bulb. Being volatile, it is sensitive to atmospheric pressure and at higher temps it boils making bubbles. Bubbles don't transfer fuel to the carbs and the engine starves and quits.
On which is which, in terms of fuel, I was under the impression the higher octane fuels had more volatile components than lower octane which in my opinion would cause them to boil more easily. I am not a petroleum engineer so I don't know. Maybe googleing the question would get you a professional reply.
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I do know this. I had a Quadrajet carb on a GM car and I wanted a better fuel filter for the inlet fuel since all it has was this little dinky thing where the fuel line attaches. The carb filter is after the fuel pump so the pump is pushing fuel through it, not sucking fuel through it. Big difference. I got the bright idea to install an after market inline fuel filter in the rubber hose preceding the pump.
On vacation the first summer after that, with the car full of kids, camping gear, the boat, AC going full blast rolling down the interstate and all that, in the middle of the afternoon, the engine died.....guess why? Vapor lock. Course I didn't figure that out till later after we got home. We'd sit and let it cool (30 minutes in the heat on the side of the road; no fan, no nothing) drive for 15 minutes or so till it got hot again and repeated the process till we made it home. The pump was sucking hot fuel through the filter I added and it boiled. Didn't take long for the modification to disappear. Boy was I in trouble on that caper. Wife took awhile to get over it.
HTH,
Mark