When the weather gets hot and your taking your car about. did you ever get a problem using todays gas I noticed a little bogging down , ended up leaning out the carb , did a little investigation and found todays gas will atomize very quickly making a problem with our all cast iron heat chambers , Just wondering if any body uses any type of additive or never noticed any difference driving in the warm weather.
The biggest problem I have had in recent years is the percolation of fuel in the carburetor flooding out a hot engine which makes restarting difficult.
A heat shield made of aluminum placed between the carb and manifold and insulation of the fuel line between the pump and carb has helped.
If you are in the experimental stage, an aluminum pie plate makes a good (hopefully temporary) heat shield.
In their day, the cars we usually talk about - 20's through 50's - had "vapour lock" problems, and this condition has worsened with newer fuels. It is essential to provide heat shielding for any downdraft carburetor and for the fuel pump if possible. If you can find them, AC used to supply extension screws for holding down the fuel pump cover (usually 2 per pump) and these provided a set-off for a heat shield between the pump and the radiated heat from the exhaust manifold. In addition, use a steel line from the pump to the carburetor (not copper) aand route it as far away from the exhaust manifiold as you feel comfortable with in terms of cosmetics. As well, you can wrap the line with reflective foil, but it's usually not a pretty fix.
Before I go crazy and re-modify or add a shield here and there is there a ideal temperature that is Safe to use , in other words its not always hot here as its been ,90 degree ,would temperatures is the 80's and 70's pretty much eliminate the atomizing of fuel?
Or Evan at those temperatures will temperatures in the hood compartment climb and still give problems Thanks for your experience and advice
Yes, it is possible to get vapour lock problems with temperatures in the 70 - 80 F range. Only experience will give you firm answers.
Wow , I was searching the web for tips ideas and I got a site for you all to see ! If you go to Yahool and type in*** vapor locking-antique automobile club discussions forms *** I think all questions will be answered and then some thoughts .... I hope this site does not get as wild as those opinions ! Hope you enjoy the site DANiel
I don;t know what area of the US you guys with vapour lock problems live, but here in New Zealand where our temperatures are more modrerate than yours we still have the same problems with vapour lock as you do. 12905 is right if you replace your fuel line use steel not copper as it attracts heat and route it as far from the manifold as possible. Chrysler corp had heat sheilds available as an accessory but they were steel not aluminium, alumnium is like copper it also attracts heat( ask the British about there destroyers in the falklands war) . To solve the problem on my two cars , a 1939 De Soto and a 1954 desoto diplomat ,as well as fitting heat sheilds i wrapped my lines with asbestos string that solved all my problems.i know that asbestos is frowned on now and can no longer be purchased in NZ ,probabley the same in the US, i bought a roll of it at a swap meet. if you cant source a heat sheild they are reasonably easy to make if you have a pattern to work from .they are the same from 1937 -1954 have made several for freinds using one that was fitted to a 1937 Plymouth that i used to own as a pattern
I have not suffered a vapor lock in my car. I dirve it in hot weather without problem. I did have a "hard start hot" problem. I have read that today's fuels ore more volitile than the older ones. Volitility has to do with heat absorbing and evaporation properties. I believe that instead of vapor lock, what your are suffering from is fuel percolation and or expansion flooding.
With high under hood temps, a couple things are going on. As it sits, the gas in the float bowl expands averflowing, and puddling in the manifold, As it drips over, the needle and seat opens, and residual pressure in the pump allows more gas into the bowl, and the cycle repeats. I have lowered my float, to shut of fuel flow slightly before factory spec. This allows less fuel inthe bowl, and makes some expansion room. I very rarely suffer from a hard start hot situation. It will exibit this symptom if the car is parked on unlevel ground, If this happens, the following method may help.
When trying to start the car after sitting while hot, slowly push the gas pedal to the floor, and hold it at wide open throttle. Then crank the engine. If it starts better, I believe it confirms the hot flooded condition. The WOT position introduces more air to clear out the flood. If this method works better, then try lowering your float to see if that helps also. Also check your fuel line on the suction side of the fuel pump. If there are any air leaks this will reduce the effectivness of the pump.
My theory on Vapor lock is "HUUUGH????" How can fluid under pressure be blocked by air in a system which is vented to the atmoshpere??? If there are air bubbles in the fuel line between the pump and the carb, the pump shoud easily pump liquid behind them pushing them out.
Air onthe suctions side is however another porblem, so make sure your line from tank to pump is in good shape.
Thank-you Ply46 I think you hit it on the mark!
Short story, Last Sunday I wanted to take the Plymouth out for a short ride ,With my daughter I decided to take it on a 9 mile one way trip to the cemetery to visits my relatives. Opened her up 50-60 for 7 miles and pulled in to the cemetery climbed a short hill ,and had to go down a short hill to start my visit. When I was driving down the road in 2nd gear it felt as if I stalled , and indeed I did . So I tried to restart at the side of the cemetery NO start , pumped the gas smelled raw gas , Opened the hood and saw indeed what u said percolation and expansion of fuel boiling out under the carb! at the base. SO since I was at our destination I visited I visited my Grandparents , and family, went back to my car no start went back for a visit , back to the car wanted to start only if I DID NOT hit the gas, (tried) went back to visit my Uncle jokingly told him ,just don't lie there I need some help!. Went back to the car did not hit the gas and it started ! Drove home all was fine NO PROBLEMS , My daughter seems to think my Uncle was showing off my car to his friends ! Either way I want to go back to visit but really am not planing to stay (Just yet )
Sorry, Plym46 but vapour lock is a fact of life; it is not a myth. Neither is it air in the lines. It is exactly as you stated, fuel vapourises because its boiling point is below the temperature of the line/pump, or both of them - take your choice. However, you are correct concerning flooding because of vapourising fuel, but not correct that the pump will simply push fuel past the vapour lock. The pump cannot function unless it is dealing with liquid fuel without any gas bubbles in it.
If in doubt, just think of a brake system with air in it.
Yes, but the brake system is a closed circuit not vented to air like a carb. Kinda like a garden hose, as opposed to a brake hose. Unless of course it diminishes the flow enough so as not to provide enough fuel to the float blowl to sustain the engine. So rather than locking, it just trying to run on a dry carb.
Short Update.......? ?I ordered and received 2 shields one over the fuel pump and one on the right side of the bell housing? (shielding the frt exh pipe),? also added my own heat Shield by the? fuel line? (next to the ext manifold).. Go figure? cool temp and rain? Will have to wait and see . Meantime I just talked to a gas man? He claims our summer gas here in Pa. has a very easy flash point, He recommend me using the winter blend ONLY..?He tells me it is double the flash point and harder to ignite than the summer gas! Seem a good Ideal to have my own personal stock on hand , I am attempting to ? the fuel aditive people to see if I can reproduce a winter Blend? , I'll keep u posted?
I think your gas guy has it backwards. Winter fuel is designed to vapourise easily at low temperatures so it contains a greater percentage of volatile fractions than does summer fuel in which the highly volatile fractions are eliminated or reduced.
NO I just take to the guy that monitors the emissions and he states in summer the gas will burn cleaner ,In winter time, so there is no stalling it is a slower burn.. and he also mentioned some racing fuel has a better burn for our cars but as noted make more pollutants He is telling me ,winter gas is better for our antique cars.
NO. If you are concerned about vapour lock, it will happen much easier with winter fuel used in the summer, than summer fuel used in the summer. Winter fuel has many volatile fractions to make sure enough of it vapourises to ignite in the cold weather.
OK , your right what the gas guy was trying to tell me summer gas is best for summer for burning the hydrocarbons and winter gas will burn quicker and indeed would boil faster, so, thanks (just in-case you might know any additive that might work ? I read somewhere some people put a cup of diesel in there tank thanks for the info! DANiel.
Darren:
I certainly would not put any Diesel fuel in the tank. I personally don't know of any specific additive to make the gas less volatile. In the past when we had to deal with flathead Fords that were the vapour lock champions of the world because of the location of the fuel pump and its line to the carb, we solved the problem by putting a baffle between the pump and the intake manifold and by wrapping the line with aluminium foil. No Chryco presents the vapour lock problem that old Fords did, so a baffle on the pump plus a steel line (not copper) to the carb that is routed well away from the exhaust manifold should do the trick. If you still have a problem it is possible to fabricate a bafle from thin sheet metal that fits between between the carb and the manifold and extends under the float bowl.