The Stovebolt Site Forums The Shop Area Engine Shop Vapor lock?

Are AD trucks or the 216s prone to vapor lock? Its been over 100*F here for the past month or so and every time I take the truck out during the day she dies on me. She runs great at night when its in the 90s.

Any suggestions on how to prevent it?

While I'm thinking about it ... would adding a lead substitute or a bit of marvel to the tank increase the possibility of vapor lock in this heat?

I doubt any additives would be a problem, but if it really is vapor lock [unusual for a stovebolt] putting some heat reflective material around parts of the fuel line closest to the engine should help - or the old Ford trick of wooden spring clothes pins on it for a heat sink

Bill

Bill,

The use of a wooden clothes pin as a "heat sink" is the remedy that is always described (and it supposedly worked). Since wood does not hold/absorb as much heat as just about any metal, do you think that the reason that this worked might have been that the clothes pin acted to move the fuel lines away from the hot engine/manifold?

I agree with you that vapor look is highly unlikely on a Stovebolt engine, especially if fuel lines are following the original routing and as long as the fuel lines are attached to the engine at the original locations (at fuel pump, at the thermostat housing, and at the carburetor or the fuel filter at the carburetor).

My experience has been that vapor lock is a sign of a failing fuel pump. Clothes pins never worked for me, only replacing the fuel pump would fix the problem on my vehicles the rare times it happened.

Same here--test pressure and flow or replace.

Problem with testing is that it only happens when the truck is at running temp and its around 110*F outside. When its cooler out flow looks fine. The pump is off a spare '48 motor and it probably needs a rebuild.

That said, I was considering switching to a pump with vacuum assist anyways. Any idea where I can find a double action glass bowl pump to fit a '51 216? ...there used to be a couple vendors with them but I can't find em listed anymore.

Dual-action 216 fuel pumps - Chevs of the 40s

Dual-action 216 fuel pump - Classic Parts

Thanks man! I knew all the vendors had the dual action metal top kind but I totally forgot about Chevs of the 40s. ...the one downside to having so many vendor options!

Ordered one dual action glass bowl fuel pump.

Before you replace the mechanical pump consider an electric pump.
I have a 46 Packard that is prone to vapor lock and have used one to push fuel past the vapor for years now. The electric pump is located near the gas tank and away from the engine compartment so the fuel is cooler. It is also nice to have a redundant system in case one of the systems gets eaten out by ethanol.
Remember all pumps are designed to pump and not suck. Once the line is filled with vapor it is having a hard time doing it's job.
I picked up a 6 volt electric for less than the cost of the original replacement for my 52 3100.

brassbolt, Can you run both an electric and a mechanical pump in series? I like the idea of keeping the original look and function but redundancy here would probably save me headaches with the low boiling point of ethanol and the absurd heat waves we've been getting.

Even though I doubt if you have a vapor lock problem if your plumbing is "naturally" routed, I think Cletis has posted a clever method of using a electric pump though an original-style glass-topped fuel pump. Maybe Cletis will correct me or post information?

There are 6v and 12v fuel pumps available that provide the appropriate low pressure, if you are using an original carburetor (and fuel filter).

The pressure from the electric pump is low enough that it has never caused any problem for the mechanical pump. I run both on hot days. It is also a great help starting a vehicle that has sat for a while. I have a toggle switch under the dash that I pump up the fuel system before turning the engine over. It will shut off when its pressure regulator reaches it's limit (5lbs). It saves a lot of wear and tear on the starter.