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PostPosted: Wed Mar 30, 2011 5:56 pm 
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I have a home built tank mounted in the front of my car,to clear the steering shaft etc I mounted the top of the tank flush to the bottom of the main tubing which makes the vent poke out of the hood.My problem is how to allow the tank to vent while preventing fuel from sloshing out.
I had tried an old circle track trick of a pcv valve directly off the tank but it splattered fuel on the hood last fall,if anyone has a solution that would be great.I'm trying to keep it looking clean and not having to run a hard vent line all the way to the rear and up the roll bar to get higher abover the tank.
Here's what I had that doesn't work. :oops:

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PostPosted: Fri Apr 01, 2011 10:44 am 
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Run a hose off the end and rout it down below the hood line. Put a breather type filter on the end to keep the dirt out also.


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Fuel cell vent.jpg
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PostPosted: Fri Apr 01, 2011 10:09 pm 
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PostPosted: Sat Apr 02, 2011 8:49 am 
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Ok so thats the obvious answer,where's the part about keeping the fuel in the tank and not draining on the ground.I was going to buy a roll over valve but figure it likely works the same as pcv valve in that its open unless there's enough fuel pushing on it to seal it.With the vibrations/minimal fuel at any given moment I'm sure it would seal when needed.
I was thinking of a light spring inside the pcv valve to keep the ball lightly seated,if the spring is kept light enough the vacuum while using fuel should open it.I'm not sure if that would create a problem with the tank building pressure as the temps went up though.


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PostPosted: Sat Apr 02, 2011 9:28 am 
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I'm not understanding the PCV valve thing. In one direction, it would provide a small amount of restriction for fuel to exit as the force of the sloshing fuel would have to overcome the weight of the internal ball. But it would prevent the return of fuel back to the tank. Repetetive sloshes would eventually fill any tubing downstream and subsequently overflow. With the PCV valve in the opposite direction, there would be no restriction at all, Unless you roll over.

To limit the gas on the ground issue, you could add some restrictor in line, close to the fuel tank. The vent only has to allow the passage of air back and for the as the tank warms up and cools down, or as the fuel is used up. A very small orifice would allow this. 2nd, after the orifice, provide some amount of hose volume to "hold" the little fuel that passes. then it will drain slowly back thru the orifice into the tank. So the system might be, fuel tank -check valve (?) - orifice - tubing.


I don't know if you have enough room to fit this all.

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PostPosted: Sat Apr 02, 2011 10:37 am 
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Not sure this is a complete help, but here is what I need I do in my formula car. I think an important thing is to route the fuel breather in a loop. In my FF it goes down to the bottom of the car and then back up to the top, it is an 18" diameter circle around the inside of the roll hoop basically. That way the tank does not drain, whether it's rightside up or upside down. The fuel tank is under my back, so it could be bad if it drains...

Whatever other solutions you land up with, this is a good extra plus for everyone's setup, I think. I don't think I ever get fuel in that line, but maybe I just never notice.

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PostPosted: Sat Apr 02, 2011 3:29 pm 
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Rx7-I hadn't thought about any fuel that gets by being trapped,good call as I think it'll be a problem as you pointed out.I think I'll make restrictor of some kind,a small lenght of hose and a filter.I didn't have any foam in the tank when I ran it last year but I think'll I'll jam some in.(had bad experience with before breaking down and clogging the filter in another car)

Horizenjob-thanks for your idea as well,I'm limited for space with the front mounted tank but if the other method doesn't play out I'll give it a shot.

Thanks


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