Re: Vapor lock poll

Posted by BH On 2009/7/2 8:01:07

Merriam-Webster Online defines vapor lock as:

Quote:
Since a diaphragm type fuel pump can only move liquid, NOT vapor, vapor lock results in fuel starvation to the carburetor. With insufficient fuel, I don't see how vapor lock could ever cause backfiring through the carb.

More likely, Craig experienced fuel percolation or boiling of the fuel in the carburetor of his Patrician. While there was no definition at M-W Online, the underlying cause is the same as vapor lock. However, when percolation occurs in the fuel bowl, the boiling fuel is forced right up through the bowl vents and into the throat of the carb. Usually, this will occur after a hot shutdown, and the condition is also referred to as a hot soak. (This was a BIG problem with carbureted Chrysler vehicles back in the 1980s, when I was a "factory rep.) At the very least, the flooding that results from this condition makes an engine difficult to re-start, but I can see how it could set the stage for backfiring through the carb.

We ran into a hot restart with a V8 Packard at another forum past, and I pointed the owner in the direction of obtaining some phenolic board to make a thin spacer that would then be sandwiched between two base gaskets - hoping to insulate the carb from heat transmitted through the intake manifold. He had a little trouble finding the right material (and I suppose he could have used some fiberglass sheet stock, instead), but he reported that the spacer cured his problem. Of course, you'd also wanna cover the same checkpoints that would cause an engine to run hotter than normal - cooling system, ignition timing and advance, exhaust manifold heat valve, etc.

My point is that one should not confuse these two conditions, which have different outcomes.

I now return you to PackardV8's survey.