Eliminating vent lines on gas tank

[RebekahsZ]

I recently had my stock tank cleaned out and removed all but one of the vent lines. My tank was filthy and I couldn't get all the scale out of it after two trips to have it boiled out. Found a local hot-rodder who filled it with exhaust off of the tailpipe of his truck and cut two big windows in the top of it. He cleaned it out completely and welded the two big windows back up. I was tired of spending so much for NOS vent lines every 10 years after having them stink for 5 years, so I got him to cut off all the vent lines except the one at the top closest to the fuel level sender and weld patches over the holes. He sealed it with some red stuff and I installed it. Ran a 3/8 inch hose from the remaining vent line up into the fender where the old evap tank was. It has a Fuel Safe rollover valve installed (it literally shoves into the fuel line). Then the vent line comes back down out of the inner fender and I had it open at the level of the bottom of the tank with a Fuel Safe Filter on the end of it. Works great. Yes, as some forum members warned, it does require slower filling of the tank above the 1/2 way point, but I can completely fill the tank and it is working fine. Only thing I would do differently is install a 90-degree bend on the remaining vent fitting on the tank. That line requires an immediate 90-degree bend to go thru the frame rail and it is a real pain to get it to turn witout kinking. I've had lots of guys tell me that you need all those vent lines, but you don't.

[emeraldlion]

I just got done handling my tank. Fortunately my tank was in much better condition. Had it boiled and sealed. Radiator shop put a decent dent in my tank but oh well. I capped off the small vent line next to the fuel sender and ran the 5/8 "burp" tubing up to the filler neck. I figured the gas cap probably doesn't seal that well and any vacuum created by the carb fuel pressures will just draw past the cap. I shouldn't have problems filling with the burp line in place.

[Tony D]

I used a 15mm to 10mm 90 degree nylon barbed adapter to make the transition easier. Also on the rearmost right tank vent (1/4") I made a "U" bend from stainless to make it fit better. All my vent lines are connected, but they are only 10mm or 5mm fuel line. I don't have to fill slowly, the 10mm seems to vent fine, you just need all the points connected. Maybe the combination of 10mm and 5mm off the back is what does it.

 

On my 74, the back right vent is what I hooked up similar to what you did: Bring it up high in the "C" pillar above where the stock expansion tank is where I put an 'instrument loop' (double wrap about 3" radius) of fuel line, and then brought the line back outside the passenger's compartment and put the rollover valve and a small K&N Gauze filter on the end.

 

Seems to work fine for me as well. As long as there is enough line volume to handle gas expansion when you fill up, nothing will pressurize or puke over. ( I still content gas expands when it gets hot...)

 

Another thing nice is the fumes---I can put 5psig in my tank and it won't leak down over night. Any fumes I get I KNOW are not tank sourced. If you plug your carbon cannister vent line, or the diverter valve on the earlier 240's, you should be able to hold 2psi in the tank overnight. If you don't, you have a leaking line---most likely a vent, and it can cause gas fumes to be smelled.

 

Main factor for me was cost as well, I put the fuel line conversion in years ago, and those lines are still fine. Even if they weren't the line is CHEAP to replace once the nylon conversion fittings are on there. These fittings were the same as Datsun used originally, I found them in a plumbing supply section at a hardware store. They had nylony, ABS, even brass. Since Nissan/Datsun used Nylon as an OEM choice, that's what I used, and they were cheaper than brass. Don't see a need for the weight and durability has not been an issue.