Is there any negative effects of plugging the EEC (evaporative emission control) valve on the top of the fuel tanks or should I just let it vent to atmosphere? Will the tanks still vent correctly if I plug the EEC vents?

 

If it's your only vent, don't plug it. If the tank doesn't vent, then it will build up pressure and possibly vacuum. Over the long term, this causes the tank to flex and fatigue, and possibly rupture. In the short term, it might wreak havoc with your fuel pump and pressure. I think excess tank pressure has been known to blow out diaphragms in mechanical fuel pumps.

 

Something something vented gas cap something or other... sorry I couldn't be more specific.

Keep it venting to atmosphere through an activated carbon filter, AKA the evaporative cannister. This emissions system doesn't hurt performance and IMHO should not be disabled.

 

The ports can be plugged if ya switch to a vented gas cap.

A carbon canister isn't a big deal so mine is still connected although the canister vents to atmosphere instead of the air cleaner.

 

X2 on what HIO said!

 

The only other advice is to not tamper with it if you still have to smog the truck.

 

EEC = Electronic Engine Control System aka onboard computer. The only vehicles of this vintage with EEC were sold new in CA 1979 LTD/Grand Marquis 351W

The Evaporative Emission valve (aka rollover valve) located in the top of the fuel tank has a nipple on it. Remove the hose and cap it off.

The problem you may have is...the non vented fuel cap uses a different filler tube than the vented fuel cap tube.

Originally the non vented fuel caps had 4 nubs, 2 above, 2 180 degrees below. The Evap/Em tube had a restrictor that only allowed a gas station nozzle used with unleaded fuel to fit into.

Back then, there were two different sizes of gas station nozzles. The nozzle used with leaded fuel was larger in diameter.

 

Drill a small hole in the cap?

 

My truck had the carbon canisters tube to the engine caped off. All the smog was removed when the last owner replace the 360 with a 65 date code 390. rebuilt bored over.03. So if run a line to vent to the air cleaner will it be safe? like the breather sided on the valve covers for the block not the vacuum on intake for the pvc valve. I have added a sealed filler cap and door so I need to vent the tank but want to avoid the gas fumes when in the garage

 

Only Galaxie/LTD/Thunderbird and full sized Merc's had a 390 in 1965, not available in F100/350 until 1968.

I suggest you measure the stroke to verify it's a 390, because on sale day, 352/360's magically become 390's!

Stroke: 352/360 = 3.50" / 390 = 3.78"

 

its a 390 I measured the stroke when I had the pan off to replace the intake when the truck was tore down and the engine was out.