Fuel tank vent?

[KooK]

For people with large, aftermarket fuel systems. What are you guys doing for venting the fuel tank? I'm trying to avoid an issue where I have vacuum in my tank and I'm not sure what point I should be concerned about it. I'm just running twin Walbro 450's

 

[Kyle_KleinSS]

I left mine hooked up as normal when I installed my fore stage 2.

 

[KooK]

Do you remember what fuel pumps you went with?

 

[SlowSVT]

Is your evap system still in place?

 

[KooK]

Not even close, the whole evap system is gone. I have a brand new smaller vent (the one Ford discontinued first) and can get a brand new larger one still. Either that or I'm thinking of having somebody make up a couple of blockoffs that I can drop in there, drill one out and put a -08an rollover-proof vent in.

 

[SlowSVT]

A vented gas cap or one with a small hole drilled in it should do the trick. A rollover vent is not a bad idea either but I would use an AN6 or smaller an 1/8" opening is more then adequate. Be very careful with what ever you do and make sure safety is priority 1 when it comes to the fuel system.

Here is a good source for fuel system components

http://kinsler.com/

 

[SVT_Troy]

I used this rollover vent valve in another platform I'm building.

http://www.summitracing.com/parts/tnk-vvr

 

[KooK]

A vented gas cap or one with a small hole drilled in it should do the trick. A rollover vent is not a bad idea either but I would use an AN6 or smaller an 1/8" opening is more then adequate. Be very careful with what ever you do and make sure safety is priority 1 when it comes to the fuel system.

Here is a good source for fuel system components

http://kinsler.com/

I'm a little surprised to hear you say to use a 6AN or smaller. Can I ask why that is?

 

[SVT_Troy]

I'm a little surprised to hear you say to use a 6AN or smaller. Can I ask why that is?

a 6an Is plenty for a fuel vent unless your running a big pump and fuel supply lines for let say 1000+ RWHP.....

 

[SlowSVT]

I'm a little surprised to hear you say to use a 6AN or smaller. Can I ask why that is?

Ever pour gasoline out of a can with the vent closed then pop the vent open which are very small compared to the size of the spigot? It doesn't take much venting to free-up the flow out of the can. A cubic foot of air will squeeze thru an orifice a lot easier than a cubic foot of gasoline.

To be honest when I answered your post I didn't spend much time thinking about your venting issue. One of my concern was venting compounds that evaporate from the gasoline to atmosphere (think of it as leaving the cap off a gas can) with a valve that doesn't seal. Not a big deal short term but something I would not want over an extended period. Then I remember what I did on my airplane fuel system that addressed this which was a "trap door check valve" (not a ball type check valve). The trap door uses a light spring to block-off the inlet to seal the tank but takes very little pressure to break the seal equalizing the tank pressure to ambient. The gas cap came with a tiny 1/32" hole to prevent any over-pressurization in an unlikely event the tank would bloating or even bursting from internal pressurization.

This is what I used but in an AN6 (note the term "flapper valve) DO NOT USE A BALL TYPE CHECK VALVE!

https://www.holley.com/products/plu...f6QdU7HHDh12z_jCg73VcV2T3X4aCTZfgwBoCq0jw_wcB