Datsun Roadster Forum-311s.org

I was looking on the site's "Album" section, and clicked on a pic from "Itsa68"'s engine picture titled "everything seems in place" or something like that......the engine seems to be a 1600 like mine, but I noticed that there are individual fuel lines going to the floats, but I don't see the line with the valve that returns to the tank......am I missing it or is that how it's set? And if it is in fact as I see it, what's the deal?

Thanks!

Jorge

Jorge:
I have not had return valves on any of my stock 1600's.
Only the fuel overflow tubes and fuel in lines are attached to the float bowl covers
The parts book carb figure shows the return valve and is labelled with "FOR USA".
Maybe the valve is also applicable to smog type engines, but I can't say for sure as I have only owned non-smog types.

Hopefully Sid can shed some light on this matter!

Sid.....any input?

Ray B.

Ray:

Thanks for the "first-hand" information. I found that very interesting specially since on the "pre-adjustment" days with my engine, A LOT of gas was going back to the tank(although it doesn't look like it's happening anymore).

So you basically rely on the overflow drains from the floats then? And last question.....in terms of performance and/or engine efficiency, does it make a difference to have it this way?

Thanks again Ray!

Jorge

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I don't think that is a fuel return line. I think it is a vapor return line. Is liquid gas supposed to flow through the valve? With no pressure regulator in the system it seems that the system wouldn't work properly if gas flowed through the return line.

Andy could be right that the valve is a vapour return line.

If my float valves are setup incorrectly for fuel level or a piece of debris prevents them from seating properly, the float bowls will overflow and dump out of the tubes.
If the float fuel level is correct, no fuel is dumped out out of the overflows.
The metal overflow tubes are routed away from the exhaust and then extended with fuel line which are clipped to brackets attached by the oil pan bolts.
Hot exhaust and fuel dont like each other...............FIRE

Performance or engine efficiency is not effected by not having a return valve.
Dumping gas out the overflow tubes is not good for gas mileage and not the best thing for the environment.

Ray B.

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Thanks guys. This has been quite an interesting discussion.

Jorge