Packard Forum Index » V-8 (1955-56)

THis is a 2wo question poll.
Are u experienceing vapor lock symptoms THIS year ???
Did u experience vapor lock symptoms during 2007 ??? (2wo years ago)


Of course this assumes that u have been driving your vintage car for at least the last 3hree years.

No.
No.

No.
No.

No and no, but the hottest it's been this year is about 50F! My Packard has never had a vapour lock problem in the 8 years I have owned this car.

I have been driving 1955 and 1956 Packards since 1960. Never had Vapor Lock. In fact, I can't remeber having vapor lock on any car.

No and No, but that is because I installed an electric pusher pump about eight years ago.

The last occurrence of vapor lock before the electric fuel pump install was so bad that it caused a backfire through the carb. The resultant pressure inside the 4GC blew out one of the pressed-in lead plugs in the carb body, which was then expelled. This caused a fuel leak which then started blowing fuel all over the engine. I'm lucky my 55 Pat did not go up in flames.

This is probably an issue like the dreaded BTV. Do not install an electric fuel pump at YOUR PERIL!!!

Any number of polls or opinions to the contrary will not prevent the odd occurrence from killing you or somebody else or destroying your Packard. Remember what the FAA and NTSB does after the odd airplane crash.

Craig

My work car: yes
no

While not a Packard, my daily driver began locking up at a particular point in my drive to work. Car is at it's hottest at that time and doing the hardest part of the drive. I have a large hill either coming from or going to work and it only did it going to work in the evening. I've since "cured" the problem by changing to a different carb design.

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.

While I don't know which V8 carburetor was involved in the backfire, don't forget that the fuel bowl venting was different in 1955 and 1956 on the Rochesters. In 1955 the anti-percolator valve used a linkage to open it when the throttle valves were closed, and to close it as the throttle valves opened; proper adjustment is important. The 1956 Rochester used an internal vent, no valve per se and no adjustment. I think the WCFBs also used a linkage to open and close the percolator valve.

Poll question answers:

1. No.

2. No.

Comments:

1. No electric fuel pumps.

2. We had a discussion on fuel pump insulation some time back. That is, many fuel pumps had an insulating gasket between the pump and block, insulating sleeves in the pump for the cap screws attaching it to the engine block, and insulating washers under the cap screws. Plus there are carburetor and fuel pump heat shields.

Edit: Neither of my Packards has the insulation parts.