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Anyone cure the vapor lock issue with today's gas?
Vapor lock isn't a byproduct of "today's gas."
Any tips on how to prevent it? After driving for awhile on hot days I get hesitation.
What engine, how fresh, is it mostly stock or modified, what Carb?
383 6.3 stock engine ,new plugs
stock 2 barrel carb
That's not "vapor lock".
Vapor lock is when the fuel gets hot enough in the line to turn from liquid to gas. Most of the time you will get that from sitting and the engine compartment doing a hot soak and the gas in the carb and lines are affected. The car won't start.
Your problem could be accelerator pump, timing, float level, too lean and on and on.
Yes and no. Ethanol laced gas does have a lower boiling point, but really the cause is from something making the fuel lines/carb too hot. It just happens a little easier.
Winter mix gas does the same thing.
I did notice if I put in 87 octane the engine will die and won't start back until 30 minutes or so. Then will fire right up like nothing.
93 octane it wont die just hesitate when accelerating.
A couple of easy things to check. To take the vapor lock question out of the picture, but @Big_John is most likely on the right track.
If you want to minimize vapor lock potential here are some easy things to check.
First, is your Heat Manifold Valve on your right exhaust manifold opening up all the way? If stuck shut, or only opening part way it will heat up your intake manifold enough to vaporize the fuel in your carburetor. Second, Is your fuel line from the pump to the carb laying on the water pump or intake. The heat from your engine can vaporize some of the fuel in the line. line should not be touching engine.
Third, does the top of the fuel bowl have a little vent cap or flap that allows the bowl to vent when shut off or idling? Check those simple items first.
But if it is running and hesitating, start with Big_johns direction.
Heat Manifold valve
That is classic "vapor lock"
This could be caused by a lot of things, but since you do have some issues with heat (causing the vapor lock) then it would be prudent to start checking some things that are causing excess heat. As @HWYCRZR has suggested, a really good place to start is the manifold valve. Those get stuck and cause all sorts of shenanigans because of the excess heat.
Do I need to replace the fuel sending unit to allow a return?
i run my '65 383-4 on 87 octane pump gas. never a problem. take no precautions storing it over winter and it starts every spring. runs like a champ.
I checked the heat manifold valve. Is it supposed to move and spring back? Mine just moves and stays where I leave it.
It is supposed to move freely. There should be a spring coil that as the engine heats up it it tightens and moves the butterfly in your Manifold to the open position. When it is cold the valve closes directing the exhaust across the intake to help warm up the engine.
Here is a link to the solvent that is recommended. I picked up a can today from the local Dodge dealer.
What did you do to your C-body today....
Thanks. I'll pick some up tomorrow. That's my main problem. It doesn't move freely and difinetly wont return back to normal.
Thank you! The heat manifold valve is the start of my problem.
Taking care of that should at least get you started down the right path to help solve some of the vapor lock issues. Spray the heck out of the shaft, springs and try to get some in the little pin holes on the manifold where the shaft runs through. Good Luck