66 Dart Gas Cap

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rod7515

rod7515

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Should the Gas cap on a 66 dart be a vented cap?

My reason for asking is I am trying to trouble shoot a problem that I have after I drive the car and then it sits for 5 minutes and on restart it seems to flood or be vapor locked.

Thanks Rod
 
rod7515 said:
Should the Gas cap on a 66 dart be a vented cap?
Click to expand...

I don't think so. My 66 Valiant has a vent tube on the filler tube, and a sealed cap. Look in the trunk, if there's a tube about 3/8" in diameter up near the filler neck, you can do a sealed cap.

YMMV, and if someone who knows more than me (which is everybody) says something different, pay attention to them.
 
rod7515 said:
Should the Gas cap on a 66 dart be a vented cap?

My reason for asking is I am trying to trouble shoot a problem that I have after I drive the car and then it sits for 5 minutes and on restart it seems to flood or be vapor locked.

Thanks Rod
Click to expand...
My Dart (273)was hard to start after sitting when hot .I installed a better spacer between the carb and the intake ,problem solved for me .Hope this helps
 
Yup, probably carb percolation. As PK mentioned, add a spacer to help keep the heat off the carb. Otherwise, you need to hold the throttle wide open on a hot start up to clear the extra fuel.
 
They are noted for that. Carter AFB/ Edelbrock carbs are worse but any carb Mopar used can do it. I can hear mine boiling when I shut the engine off and open the hood. Today's gas is also a big factor. Ethanol boils around 150° so it happens pretty easy.
 
It's interesting that Mopar tried to fix the problem with an intake gasket with just a pin hole on one side in the exhaust crossover port. That worked pretty good until that pin hole plugged up with carbon and then there was no heat going through the intake at all. Then the choke didn't work right and sometimes the carb would ice up under certain conditions.
 
I’ve already put on an insulator pad under the carb plus I’ve added a spacer. It’s not a stock setup as I’ve replaced all fuel lines and I’m thinking one of the issues is that the return line in the system creates pressure when dumped back into the tank. I run a Mallory electric fuel pump with a regulator and 5.5 - 6 lbs of pressure. That’s the reason I ask about the vented cap. I’m going to be switching over to a 2x4 set here shortly but was hoping to figure this out first.
 
Unless you sealed up the filler neck vent tube, there should be no pressure in the fuel tank. With a sealed fuel cap, the tank will vent any pressure to the atmosphere through that vent tube.
 
Fuel percolating is my answer. A vented cap, tank, or a return system won't stop gasboiling and evaporating after you shut the engine off.
 
Thanks for the reply’s. I ran the fuel line up the inside of the passenger side frame rail. I think the worse issue is that the header on that side is about 2.5” below the gas line at the collector and then as it runs up inside the engine compartment where it gets to much heat from the header coming off that side of engine. I’ve already covered the lines with heat reflector but it’s not helping. Has anyone tried to run the fuel line somewhere else and if so how did you route it?
Rod
 
If you're running a full fuel loop back to the tank with an electric fuel pump, vapor lock is not the problem.
 
My vent tube on the ‘63 was plugged with crud. Built pressure in the tank.
 
I was fighting hard starts when my 64 valiant was cold. A little starter fluid and it would fire up but not on it's on. I replaced the original fuel pump with a new mechanical pump which didn't help only to find my manual choke cable had come off the carb!
 
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