1955 vapor lock?

[RichD]

hi... my '55 Ford, 272, frequently stalls after running awhile. I've replaced the carb, filter, and fuel lines. Could this be vapor lock? Runs ok when cold. When it does stall, it cranks slow. After a few minutes sitting it fires.

[Guest papete]

It will only vapor lock in really hot weather. How is your gas tank. It could be dirt in the line.

[Guest simplyconnected]

My original '55 Ford tank has a pick-up tube with a fine-mesh screen, situated much like an oil pick-up in your oil pan. I bought a new tank, and for the heck of it, I cut a 'window' in the old tank, to see what's going on. I couldn't believe... I pulled out HANDFULS of rust, like about five of them. My 272 would idle ok, and it would cruise at 45, but that's it. Gas was too choked off to go any faster. At times it would stop.

Your fuel filter is good for the tiny pieces that get thru the pick-up screen, but after seeing all that rust, seriously, I don't know how it ever ran at all.

Vapor lock happens when gas boils. Gas boils (at atmospheric pressure) from around 100-400º F. When it is at negative pressure (suction) the boiling point goes down.

If your fuel pump pulls, but the pick-up screen is blocked, and the outside temperature is hot, your gas will boil. High elevations aggravate things too, because the atmospheric pressure just went down, lowering the boiling point further. A tiny leak in your fuel line will suck air bubbles, again, if your pick-up tube is blocked. Turning off the car will back-flow rust particles and ‘reset’ the pick-up screen until it loads up again.

When we went to gas tank fuel pumps and a recalculating system, all those problems went away forever. Now, gas is always at positive pressure, causing a higher boiling point.

[Ron of Chicago]

Are you sure that it's a fuel problem?

Ron