Packard Forum Index » Pre-War (1899-1942)

Someone once said that most fuel problems are electric and most electric problems are fuel. Never the less, go back to the basics and make sure the three, combustion, electric and fuel are all up to spec, in that order.

That said a small amount of diesel fuel did cure the vapor locking problem I was having with a 47 Custom.

Also, the distributor vacuum chamber (advance) is often a problem with a poor running engine. Make sure it will hold vacuum and the mechanism actually moves to advance and retard the timing.

Happy New Year!

29 Guy - I seem to recall you had an issue with your shutterstat failing -- are your shutters opened when you've noticed the problem? If your shutters are closed, then that's your culprit. But, if they're opened at operating temperature then take your IR thermometer, and take the temp of the upper radiator neck, the lower neck, then shoot across the water jacket from front to back and report the results. The upper neck should be the hottest, the lower should be the coolest, then the water jacket should be fairly consistent with lower neck temperature.

Shutters didn't fail but I did just open them and disconnect them, no need for them down here, it's always too hot. Don't have an IR thermometer I'm afraid.

IR thermometer ordered, didn't realize you could get them that cheap!

The Packard Club newsletter published a series of articles on vapor lock just recently.

That article was really good, but your situation with already using an electric pump takes away much of what the article covered. I use only an electric pump as well. I too use my 901 in southern weather ( SC ) and seldom drive it if the temp is over 85. When I do, I get that same 180 temp which I do not like. That is a good way to blow a head gasket, something none of us wants to experience. My car usually runs at the 165 prescribed by Packard. My car too has the shutters blocked open for max air flow. If the situation only happens when the engine is hot, or the ambient temp is above 85, then I would look to your gaskets. It does not take much loss in vacuum, to show up in performance. Check the intake manifold gaskets when hot, also the carb gasket. A small leak can cause this and is the cheapest easiest thing to trouble shoot. I find most times a simple fix is the ticket. I don't like the diesel fuel thing, it is more snake oil than anything. Use non-ethanal gas in the 90-93 octane range if you can find it. I find that my car starts and runs much better with it.

On my 29 I found that the water jacket gasket was not correct . There is a company that is selling reproduction gaskets that are not correct and the rear cylinders overheat. The correct gasket should be rectangular with a small area of gasket about an inch from the front going from top to bottom. That way the the water is getting forced into the water jacket. Some of the reproduction gaskets do not have that small area and it’s just a rectangular gasket going around the outside edge

Ethanol slows the burn rate which makes the engine run hotter. That can be patched by changing carburetion which will increase fuel consumption even further.

According to a Packard service bulletin vapor lock in updraft carbureted engines takes place inside the carburetor.

The diesel fuel thing is something Model A owners have been doing for a long time. It actually provides a level of top cylinder lubrication, but also likely reduces performance. If there are air leaks in the system it helps to reduce that too.

And yes, I have gotten gaskets that are not made to pattern from reputable suppliers. It is a disappointing experience the same way as drop shipping scams on the junknet. Inspect all parts prior to assembly.

The engine was rebuilt approximately 800 miles ago by a very reputable Packard engine guy in Minnesota, and has been running fine up until last week, so, with all respect, I don't suspect a head gasket or water gasket to be the problem. The engine doesn't seem to be running any hotter than normal.

I would assume that your 1929 Packard is in good running order under all normal conditions, as were my two 1929 Packards. Mine started, idled and ran well under all conditions except when it was particularly hot weather and then they sometimes vapor locked.
Vapor lock does not happen all the time, only under adverse conditions. When it happens the engine will run for a second then starve for fuel for a second and keep doing that until it either corrects itself or the engine stalls. It might happen on a long steep climb and be fine when it is back on the flat and not working so hard. It might happen in stop start conditions when there is less air flow through the radiator. It never happens in cool or cold weather.
The problem is caused by the fuel in the carburetor boiling. When that happens the fuel drawn into the engine is intermittently either normal atomised liquid or vapor from the boiling fuel. The vapor has little energy so the engine starves and misses.
The problem starts in the vacuum tank where the fuel is heated by its proximity over the exhaust manifold and from engine bay heat. The fuel will boil in the vacuum tank. I have proved this by removing the top when it has happened on my car. Even though it is boiling it flows under gravity to the carburetor where it continues to boil. The boiling fuel is drawn through the carburetor to the engine as a mixture of liquid and vapor which is what causes the erratic running. There is negligible energy in the vapor so the engine starves for fuel.
Fixing the problem is not entirely possible under worst case conditions. Everything possible must be done to reduce the temperature of the fuel and that is far from easy. A heat shield under the vacuum tank is essential. An electric pump bypassing the vacuum tank is probably the best solution as there will be far less fuel exposed to the very high engine bay temperatures so it will be cooler when it reaches the carburetor. An electric pump feeding the vacuum tank does nothing to solve the problem. Getting the fuel to the vacuum tank is not the problem.
Another solution is to raise the temperature of the boiling point of the fuel. The fuel does not have a single boiling point like water, it is a mixture with many different boiling points, the lowest being around ambient temperature on a hot day. Mixing kerosene with the fuel raises the average boiling point of the fuel mixture, it dies not change the boiling points of the fuel components, it simply provides more higher boiling point fuel. I have spoken to fuel companies who have confirmed its effectiveness and that it is not detrimental to the engine. However the fuel needs to have at least 10% kerosene to make any difference, 20% is better. Such quantities can be difficult to obtain.
Another solution, although hardly practical, is use Avgas, available at airports. Avgas has a much higher average boiling point for obvious reasons.
These comments only apply to the models with vacuum tanks for fuel delivery. The problem may be different on cars with mechanical fuel pumps,