Hi guys, I'm in the process of planning my fuel system and am looking at installing a surge tank in the spare tire well. After looking at the return line to the stock 2g saddle tank, I'm a little worried that I will kill the function of the stock siphon. My plan is to run a -8 line from the surge tank back to the stock return line location. A -8 line is considerably larger than the stock return line.

Should I be worried about the siphon system in the stock tank? If so, is there a way to modify for a larger return line?

Any help is appreciated.

Have to drill out the siphon hole. I think to 1/8". Not sure. Search for it.

TSiAWD666 said:

Have to drill out the siphon hole. I think to 1/8". Not sure. Search for it.

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I've done that, but I'll be going from 1/2" line down to a 1/8" hole. I see a big problem with that.

wishihadatalon said:

I've done that, but I'll be going from 1/2" line down to a 1/8" hole. I see a big problem with that.

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Good for you, you've misunderstood why the hole is being drilled. You're not actually drilling the drain itself, but the source of the venturi effect that makes the siphoning occur.

TSiAWD666 said:

Good for you, you've misunderstood why the hole is being drilled. You're not actually drilling the drain itself, but the source of the venturi effect that makes the siphoning occur.

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So it's been a while since I drilled mine out, but my understanding is as follows. You're drilling the main drain out to ~1/8" depending on who you ask. The reason for it not being larger is because you'll lose the venturi effect.

I made my own siphon using an AN T fitting. I machined a restrictor and pressed it in. I kept enlarging the restrictor hole in the siphon until I could start adjusting base fuel pressure with my fuel pressure regulator. If the siphon orifice is too small then base pressure will be too high and the regulator will not be able to lower the pressure.

In your case if siphon is too small the surge tank will fill completely up and start pressurizing the whole system.

So I did have the thought of putting two returns from the surge tank back to the stock tank. Put them at different heights, so the first one would go to the factory return location and use the factory siphon. The second higher fitting would return to the drivers side pickup location. So if the system is out flowing the factory siphon and over filling the surge tank, it would overflow to the other side of the tank. No idea if it'd actually work, but I may be trying a science experiment in the future.

The siphon probably needs a little pressure to make it work correctly. May not take much though.