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I know there was a discussion on Vapor locking a while ago and would ,like to look again does anyone know where it is/
Thanks Jim
Jim,
I DK on the location on this site, but you should be in touch with George Teebay on the matter, as I recall that he has a good solution for the problem.
Peter
Jim, I used the search feature in the header-box for the message forum. I used vapor as the search word. I did not find the article or discussion you are looking for.
However, I did find a link to some interesting info regarding carburetor jetting and other ethanol-tainted fuel issues.
http://www.thecarburetorshop.com/Ethanoluse.htm
Please understand that the rejecting of the Series 80 carb is done via our ‘RICH-LEAN’ mixture control. So we can from the driver’s seat and while driving richen or lean the mixture to help compensate for the ethanol-tainted fuel.
For our Series 80 Pierces, the vacuum tank on the firewall and the carburetor both get exposed to a lot of very hot air from both the radiator and the exhaust manifold. This results in the fuel in first the carburetor bowl, then the fuel in the vacuum tank reaching the boiling point for ethanol-tainted gasoline. This temperature is somewhere around 150-160*F. The air coming through the radiator is near this temperature, then add the heat from the exhaust manifold to the air, and you can see the result will be boiling fuel.
Usually this will happen when the outside air temperatures exceeds 85-90*F
If you buy fiberglass ‘Header-Wrap’ from an automotive retailer that sells to the high-performance crowd, then wrap as much of the exhaust manifold as possible with the insulating woven fiberglass header-wrap, the heat transfer to the air under the hood will be reduced.
An air deflector around the front of the carburetor bowl, made from heavy tin foil will LOOK AWFUL but does tend to deflect the heat around the float bowl, reducing the temperature of the carburetor bowl.
I drove George Teebay’s 1925 Series 80 over ‘Fandango Pass’ on a Modoc tour in 90* weather. The fuel in the carb boiled about 1/3 of the way up the pass. I ended up using the primer as an additional [cooler] fuel source to run the engine on. I had to gently and carefully pull the Primer handle out ‘just enough’ to keep the engine running,
The primer gets it’s fuel from the ‘T’ just before the carburetor bowl, and it seemed that at this spot the fuel was still in liquid form.. The drive up the pass was ‘exciting’: one hand on the steering wheel, one metering the fuel to the engine via the PRIMER T-handle, and a third and to shift between 1st gear and 1st-overdrive. It was a very memorable drive..
When we reached the summit, the fuel in the float bowl could be heard boiling, We let the car sit and cool for about 25 minutes then took the uneventful road down the other side of the hill/pass.
So: wrap header wrap around the forward part of the exhaust manifold and especially the exhaust down-pipe from the manifold down to below the engine splash pan, this is the main source of heat to the air flowing over the carburetor.
Hope this helps.
Greg Long
Try page 30, under the topic heading “Gasoline” for pertinent information.
Avgas is blended to lower Reid vapor pressure so would tend to resist vapor lock; also is of higher quality.
Get rid of your “winter” gas and burn it in your lawn mower. Keep fresh, summer gas in warm weather.
On a recent posting in the Rolls-Royce forum, a vapor lock issue turned out to be a failing coil: so, it’s not always vapor lock, but VL gets the blame.
Good luck to all of us this summer!
Greg, that was indeed a memorable ride up the washboarded dirt corkscrew known as Fandango Pass!
The most important thing to do is to wrap the exhaust downpipe from the flange down to the splash pan. When these cars were built, gasoline lacked volatility, so the placement of the downpipe at the front of the engine added THEN-needed heat to the updraft carburetor. Today we opposite problem–fuel is too volatile for low-pressure fuel delivery systems.
I haven’t seen, much less tried, wrapped front sections of the exhaust manifold itself.
I’ve also made up easily removable heat shields to wrap around the vacuum tank. The vac tank sits, unfortunately, where exhaust manifold heat will be blown against it, and it gets heat from the adjacent rear of the exhaust manifold. I bought aluminum-face quilted sheet insulation from a performance parts store, and cut to fit, including protection for the bottom of the vac tank. You can use large hose clamps or attach Velcro.
As Greg notes, the fact that gas is still liquid at the primer line just before the carburetor bowl indicates that the “boiling” or vaporizing is occurring INSIDE the carburetor bowl. That’s why the downpipe wrap is the most important. However, I believe that anything we can do to lower the temperature of the fuel in the vac tank and in the line to the carb will INCREMENTALLY assist. Another small thing that contributes is to slit some rubber fuel hose lengthwise and cover some of the lower fuel line between the vac tank and carb.
Another lesson of the Modoc Tours for climbing long grades in hot weather, read the motometer and drive so as to minimize the heat load being produced by the engine. The more fuel it gets, the more heat is generated, so find the sweet spot (speed and gear choice) at which the engine is working “least hard” while maintaining sufficient momentum, even if not at your desired cruising speed.
Thanks to all of you for your input.
I cannot say for sure that I have a Vapor lock problem but the 85 degrees or more is when it is a problem and when the motometer is in the top circle. I have tried changing coils. Also pulling on the primer and sometimes that does not do the job I will try the exhaust wrap and try to get some pure gas. Some times the rich/lean lever does help until it gets a little hotter. I have not been able to keep going long enough to watch the motometer to find a sweet spot. Will keep at it.
Trying to be ready for Marilyn Heights.
Jim, if your car’s ailment includes running OK after it cools down, consider a defective condenser or coil, ESPECIALLY if you’re still running the original condenser in the distributor. Those old condensers have wax paper insulators under the shell and heat kills them.
You can get a modern condenser of the same value (I use one from a 1962 Ford full-size 6 in my Series 80) from NAPA. Be sure to get fresh, rather than NORS, stock. Because the modern shape won’t fit inside the distributor without modification to the plate, attach the lead to the primary lead on the coil that has the wire going to the distributor. BUT you must ground the case, as with a small hose clamp securing the body of the condenser to a radiator steady rod.
And carry a spare coil and some duct tape–a modern 6V coil (VW will do) can be taped to the steady rod as well, but no need to ground the coil’s case.
Jim,
I have a modern 6v coil and condenser mounted inside the passenger compartment high on the firewall (using the original coil screw holes – using longer ones) and have it snaking through the firewall into the loom so you can’t see it.
I kept the original wires in the loom but cut them off so that they look original but they are wires to nowhere.
I then connected the modern coil through the loom to the distributor and ditto with the condenser wire to the distributor.
You can’t tell by looking, but if you pull on the coil wire as the “original” wire enters the loom from the coil, you see that it is cut off.
Perhaps this is another upgrade to consider.
Peter
I mix four ounces of 2-cycle engine oil to each ten gallons of gasoline which helps present vapor lock as well as providing upper cylinder lubrication. With aircraft engine, the old saying is that a “rich mixture is a cool mixture”. The same is true with our engines. I have a modern temperature gauge on my Series 33. Climbing a steep grade with the mixture control moved toward rich, the gauge will show a stable or even a decrease in engine temperature.