I am assuming that was a racing suggestion not for the street cars.
The carb float bowl does need it's vent. Don't plug that one
Areas I would check (if not already done so):
- Rusty or damaged metal fuel lines (all 3 tubing sizes / 8 sections of tubing).
- Cracked rubber fuel hose (3 different sizes (5/16”, 1/4” and 3/16”) located at fuel tank, at close to passenger side firewall (kinda hidden location), at fuel pump, at fuel filter and at charcoal canister. A leak at any of these locations can cause problems – and sometimes a cracked hose will not leak fuel but will suck vapor (easier to suck air than fuel) instead.
- Make sure the air filter on bottom of Charcoal canister is not stopped up. Take a section of hose (all 3 sizes, once for each port) and blow (don’t suck, unless you like to inhale fuel vapors). Note: you will need to plug 2 of ports when blowing through the 3rd port. Some, to a lot of, restriction will be present. If you can’t blow – then you have a problem with it.
- The fuel tank is vented through the charcoal canister. Before messing with gas cap, first take a drive in which you can tell it is acting up. Remove the gas cap (or let it dangle if it is tethered to car) and take another drive under same conditions as above. If there is a noticeable difference – then you need to recheck the above items.
Note: I don't recommend driving a lot with gas cap off - for dirt is enemy #1 for fuel systems. It is OK for testing purposes.
Note: a car with a controlled vent system will get better fuel mileage than a car that has an uncontrolled vent system. Not a lot better, but anything better is always good.
My ’86 Fifth Ave, after a long trip, will percolate the fuel from the carburetor from hot soak after turnoff. In those cases, the fuel vapors travel down to the charcoal canister (on cars without a bowl vent, like my ’77) or will stay in the bowl (on cars with a bowl vent solenoid). My ’86 Fifth Ave currently has a ’77 318 Carter BBD installed on it, instead of a computer controlled Holley version (so no bowl vent). On cars with a (working) bowl vent, the evaporated fuel vapor should condense back to liquid fuel once the carburetor cools down.
Same thing happens (sorta) with fuel tank. Gasoline will evaporate at room temperature. On cars with an open vent, those fuel vapors leave the car never to be seen of again. This is not a fast process – but it does happen, more so on hot days.
Cars with a regulated fuel vent (most FMJ cars), the fuel vent goes to the charcoal canister. The charcoal soaks up the fuel vapors - instead of it going to never never land. When engine is running, there is a small vacuum hose to carburetor that applies a small vacuum on the charcoal canister which allows those trapped fuel vapors to get burnt.
I’m not really fond of the complexity nor the “clutter” of the EVAPORATIVE system, but it does work, and it is required in some states or city’s.
That said, if performing a major overhaul of engine or performance upgrades (for street usage), I will leave the evaporative system in place because it does help a lot more than it hinders.
Don’t believe that fuel evaporates at room temp?
Take a dish outside (not something from kitchen, or your better half will remove some of your hide, or plastic) and pour a little gasoline in it. Come back tomorrow and you may find it’s all gone due to evaporation. Same thing happens to water, to a lesser amount.
When i got this car the previous owner took out the charcoal canister, the vacuum pump and did a hack job on a egr delete im going to finish removing all the egr parts and tubes and plug the egr holes in each head properly or just buy some aluminum 360 heads this winter i hope, but i am going to run all new gas line, return line and vent line front to back (steel) and put my low pressure electronic fuel pump (4-7 psi) in line by the tank and make a delete plate for the mechanical pump (i work in a machine shop so it will be done rite lol) but hopefully running all 3 lines front to back with the electric pump will solve this problem I HOPE!! Thanks for all the suggestions any more input is greatly appriciated! Mopar on
If previous owner removed the charcoal canister – then I suspect, he might have capped or crimped the fuel tank vent line.
The large metal line is “main fuel” (5/16”).
The two smaller lines is fuel return and tank vapor (I think the smaller one is vapor).
Well either way its getting 3 new lines this weekend lol
A long time ago, I purchased a badly rusted out ’84 Gran Fury police parts car. One of the things I had removed was the fuel lines.
My plan is to make a set of stainless lines for each car, using 3/8” for main fuel line, using these as a guide.
Personally, I think having a return fuel line is beneficial especially in carbureted cars (vapor lock) – but I do plan on using fuel injection – so not sure what recommendation will be for that is, yet. Waiting on $ for injection system(s) before starting any line making. I do have the benefit that current fuel lines are in good condition.
I have rolls of stainless tubing in my garage and a cool set of bending tools and bubble tool/flare tool set (all from Eastwood) that I’m (sorta) ready to try out.
Here are some photos of those original fuel lines (if it helps you).
I do not recall the length, but the rear lines are all a “standard” length (maybe 16 foot – I can’t recall) – which is why I suspect there are 6 lines instead of 3.
Pre-bent fuel lines in coated steel or stainless. Granted, it would be pricey to get all 3 lines (main, return and vapor) but they are available.
I have everything to run new lines but thanks for the link any way
Ahhh...this brings back some memories!!!
I bent new lines, but stainless steel was not for this 'rookie' guy...just didn't have the tougher tools, I went all aluminum. 3/8", boy, what a much easier time it was to get all the kinks and turns.
So far I'm actually about 10 yrs into running fuel through them...no complaints, no visible corrosion that I've spotted (and I regularly go through them at the start of each season). Keep in mind, this is a weekend driver, for from a daily car, to the effect that the car has never seen wet pavement since I've actually put it back on the road.
I've always done alum line like you. It can be formed to get nice angles around a paint can
Cool find – but Wow, $110 times 3 (plus shipping and/or tax), if stainless is used.
Think it is, um, different they do not offer 5/16” metal fuel line. If a person was going through trouble to make a metal line, why mess with 5/16” - but that’s not the point.
Also, their 3/8” fuel line is 1-piece. It might be pre-bent, but then bent back into a coil to get it to fit into the box?
For fuel line, there is nothing wrong with aluminum – just if you avoid ethanol or other alcohol based fuel.
Also, for a daily driver, a small rock or something flung from the road, can kink a line – which can make troubleshooting a headache.
A weekend driven car – most people will avoid issues where damage might become an issue.
I've used 1/2" aluminum fuel line for 30 + years on the street and have yet to see it dent from a rock.
Most parts stores carry 25' rolls of copper-nickel brake line in 3/16, 1/4, 5/16 and 3/8, legal for brakelines, doesn't rust and super easy to bend and flare.
I've used the 3/8 and it does work well.
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