318 Can't keep fuel in filter, stalls when hot.

67Dart273 said
I don't know why you'd do that the stock vents worked just fine, and using a vented cap leaves you open for fuel puking all over the fender on a hot day when near full

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This sounds like a classic modern alky fuel heat problem. Modern fuel boils easier than old "pure" gas.

Putting the sleeve over the tube MAY have just trapped heat in.

Best thing I did before going to EFI was

Installing a rear mount electric pump and ditching the mechanical
Building a vapor return system using a Wix filter with a return orifice
Using thick isolator gasket under the carb

If you think its the pump/ eccentric you need to get a pressure gauge and do both a volume and pressure test of the pump

I would DOUBLE check that the tank is actually venting and I'd check the tank pickup sock for blockage, blow out the line if you have not and check for line blockage. How about the condition of the flex hose from tank to tube?

So the tank I put in looks like this. That port on top that I thought was a vent started leaking gas out if it when I filled it up. So I think that was for a return line and not a vent thats why I put a cap over it so I wasn't leaking gas. It looks more like what you slip the rupper hose over.
I blew out the line the rubber hose from the sending unit to the hardline is no more then 2 inches long and I replaced a few months last time I was under there still looks good.