Fuel return line and vent line delete

[budsaipan]

I have my truck stripped down to the frame. I'm trying to get rid of as much things as I can and was wondering if I can remove the hard lines for the fuel return line and the vent lines.

 

Can I cap the return line at the gas tank?

 

For the vent line, can I remove the hardlines and vent it below the gas tank?

[ggzilla]

You can remove the vent line up to the front if you vent the tank somehow. Stock, the tank is sealed and the stock cap is non-venting (only lets air in, not out). Old Datsun tanks from the 60s ran a hose loop up into the fender, way above the level of the tank, and back down to the frame level and just dumped to atmosphere. It was roughly 100x more tank vent pollution than the 1970s solution.

 

For the return line, it is not needed. You can cap it. It was added to 1) mitigate vapor-lock and 2) reduce fuel evaporation (fuel vapor).

[budsaipan]

Thanks. I'll take out the hard line for the vent and just leave it open on the gas tank area. As well as the fuel return line, I'll just cap em at the tank so I'll have only one hardline coming out to the front.

[datsunaholic]

Just remember, if you ever plan to run an electric fuel pump you'll wish you had kept the return line. Heck, with a Weber you'll wish you kept the line. You can solve the inevitable flooding with a fuel pressure regulator, but the stock system with an orificed return kept the fuel circulating and cool, plus avoided the flooding problem. It's less of an issue on 74 and older rigs because 1) the fuel pump was a LOT smaller and 2) the mechanical pump is dependent on engine RPM. I've had a number of 620s that had the return lines either capped or removed, and restoring the original returns solved the constant flooding issue.

[budsaipan]

My setup is Electric pump with mikuni 44s. Of course fuel regulator. So far, I've read alot havent had much issue without return lines... I guess I'll need more opinion on this or just try it out.

[datzenmike]

With the intake so close to the hot exhaust it's a good idea to circulate the fuel so it doesn't heat soak in the metal lines waiting to enter the carb. Stop and go in the summer heat will easily raise the under hood temps above the boiling point of several of the components in gasoline. 100 deg F and up. The exact boiling point will change w/altitude and the time of year- gasoline is formulated and geographical location. For example the 10% alcohol by content boils around 170 F.

[ggzilla]

One Ratsun member was having this exact problem last week.

[datsunaholic]

Having Mikunis changes a lot. Me, I'd still use the return line and ditch the regulator (I've NEVER had good luck with those) but it would take a little engineering since the original orificed return system is gone.

 

Since you've been running w/o it anyway, simply removing the lines won't hurt. Won't make a bit of difference. You're gonna want to vent the tank properly though. Just leaving the vent line open is inviting dirt and moisture into the fuel tank.

[budsaipan]

Thanks guys. I'll be removing them and putting some kind of filter for the vent line. If anything, I can always put it all back.

[ggzilla]

You don't need a filter, it won't do anything except evenutually clog up. Just make sure there's a loop so it doesn't drain out or pull dirt into it.

[Eric Garside]

One Ratsun member was having this exact problem last week.

 

That was me and I havent had a chance to hook it up but as soon as I have time that return line is getting reconnected!