Gas tank vent? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PDW HOTRODS · 09-26-2009, 10:46 AM

I installed a 1970's car gas tank under the back of my 53. It has 2 lines coming out by the sending unit. One is the 3/8 line to feed the engine, the other originaly went to the return line from the fuel pump I think. I know they also had a charcoal canister for a vent to go to. I am running a fuel pump with one inlet and one outlet, no return line. What should I do with the second line at the tank. I would like it to vent somehow so I don't get a vacume in the tank, but I think it would be a bad idea to let gas fume just flow under the truck. Is there a filter to cap this line? My gas cap has no vent either. Thanks.

63 & 64 Bowties · 09-26-2009, 04:44 PM

Doesn't that return line go as "deep" in the tank as the suction line? If so, I would worry about a siphon effect if you used it as a vent, unless there's an inline check valve still there.

OrrieG · 09-26-2009, 11:37 PM

If its a true vent run a hose with a roll over filter used for racers up the nearest stake pocket. If it is as deep as the pickup line then just cap it off with a hose and fitting and run a vented cap. If the inlet is out the back you may run into problems going up steep hills, I had a late 60's chevy tank as a second tank in mine. In hilly country had to make sure I was running off the main tank and had a non vent cap on the back. Around town did not have any problems as long as the tank was down a few gallons.

**truckdude239** · 09-27-2009, 08:41 AM

i would just cap it off and add a vented gas cap

PDW HOTRODS · 09-27-2009, 11:08 AM

http://www.yogisinc.com/detail.cfm/-...m=Yes/zoom.htm
This is the type of cap I alread have. The return line stops at the yery top of the tank. My cap is already installed, and I would like to leave it if I can. Is there some kind of one way valve for a vacume line I can put on the end of that vent line? I know power brake boosters use a one way valve, maybe I could make one of those work.

63 & 64 Bowties · 09-27-2009, 11:27 AM

I'm not sure you'd want to go that route. I think you need PV venting (pressure & vacuum) otherwise, what will happen if you fill the tank and night when it's cool outside, then park it in the daytime sun?

OrrieG · 09-27-2009, 01:19 PM

Quote:

Originally Posted by PDW HOTRODS

http://www.yogisinc.com/detail.cfm/-...m=Yes/zoom.htm
This is the type of cap I alread have. The return line stops at the yery top of the tank. My cap is already installed, and I would like to leave it if I can. Is there some kind of one way valve for a vacume line I can put on the end of that vent line? I know power brake boosters use a one way valve, maybe I could make one of those work.

I mentioned it in my first post here is a link.

http://www.summitracing.com/parts/BOB-90921/

There are at least half a dozen more there.

hotrodrookie · 09-29-2009, 12:38 PM

Im getting ready to plan out my fuel system and Im going to be running an under bed tank. Im I ok with running a vented gas cap or should I tap the tank and plumb in a rollover vent/valve? Can the rubber hose be run below the tank or should it stay above the level of the tank in the fender well?

http://www.yogisinc.com/Detail.cfm/-...vv/product.htm

Tri5Nerd · 09-29-2009, 02:11 PM

Quote:

Originally Posted by hotrodrookie

Im getting ready to plan out my fuel system and Im going to be running an under bed tank. Im I ok with running a vented gas cap or should I tap the tank and plumb in a rollover vent/valve? Can the rubber hose be run below the tank or should it stay above the level of the tank in the fender well?

http://www.yogisinc.com/Detail.cfm/-...vv/product.htm

I think your computer has that information programmed into it, to automatically cut the fuel to the tank if there is a incident. I remember reading this on another (LS1)forum.

Tri5

hotrodrookie · 09-29-2009, 02:18 PM

I dont mean to hijack, but the reason I asked, is im gona run a pump similar to the tanks inc pump and I figured I should vent the tank. The screw in tank vent stops fuel from pouring out if ever turned over but mainly serves as a vent for fumes to exit the tank.

Any info on routing the vent tube?

09-26-2009, 10:46 AM	#1
PDW HOTRODS Registered User Join Date: Nov 2006 Location: Sutherlin Oregon Posts: 502	Gas tank vent? I installed a 1970's car gas tank under the back of my 53. It has 2 lines coming out by the sending unit. One is the 3/8 line to feed the engine, the other originaly went to the return line from the fuel pump I think. I know they also had a charcoal canister for a vent to go to. I am running a fuel pump with one inlet and one outlet, no return line. What should I do with the second line at the tank. I would like it to vent somehow so I don't get a vacume in the tank, but I think it would be a bad idea to let gas fume just flow under the truck. Is there a filter to cap this line? My gas cap has no vent either. Thanks.

09-26-2009, 04:44 PM	#2
63 & 64 Bowties and a few others Join Date: Jun 2007 Location: Blue Ridge Mountains of VA Posts: 5,638	Re: Gas tank vent? Doesn't that return line go as "deep" in the tank as the suction line? If so, I would worry about a siphon effect if you used it as a vent, unless there's an inline check valve still there. __________________ Bill US Army Vet -193rd Infantry BlueRidgeMuscleCars.com “The greatness of a nation and its moral progress can be judged by the way its animals are treated” Gandhi

09-26-2009, 11:37 PM	#3
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: Gas tank vent? If its a true vent run a hose with a roll over filter used for racers up the nearest stake pocket. If it is as deep as the pickup line then just cap it off with a hose and fitting and run a vented cap. If the inlet is out the back you may run into problems going up steep hills, I had a late 60's chevy tank as a second tank in mine. In hilly country had to make sure I was running off the main tank and had a non vent cap on the back. Around town did not have any problems as long as the tank was down a few gallons. __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project

09-27-2009, 08:41 AM	#4
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	Re: Gas tank vent? i would just cap it off and add a vented gas cap __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

09-27-2009, 11:08 AM	#5
PDW HOTRODS Registered User Join Date: Nov 2006 Location: Sutherlin Oregon Posts: 502	Re: Gas tank vent? http://www.yogisinc.com/detail.cfm/-...m=Yes/zoom.htm This is the type of cap I alread have. The return line stops at the yery top of the tank. My cap is already installed, and I would like to leave it if I can. Is there some kind of one way valve for a vacume line I can put on the end of that vent line? I know power brake boosters use a one way valve, maybe I could make one of those work.

09-27-2009, 11:27 AM	#6
63 & 64 Bowties and a few others Join Date: Jun 2007 Location: Blue Ridge Mountains of VA Posts: 5,638	Re: Gas tank vent? I'm not sure you'd want to go that route. I think you need PV venting (pressure & vacuum) otherwise, what will happen if you fill the tank and night when it's cool outside, then park it in the daytime sun? __________________ Bill US Army Vet -193rd Infantry BlueRidgeMuscleCars.com “The greatness of a nation and its moral progress can be judged by the way its animals are treated” Gandhi

09-29-2009, 12:38 PM	#8
hotrodrookie Registered User Join Date: Sep 2008 Location: Sacramento Posts: 425	Re: Gas tank vent? Im getting ready to plan out my fuel system and Im going to be running an under bed tank. Im I ok with running a vented gas cap or should I tap the tank and plumb in a rollover vent/valve? Can the rubber hose be run below the tank or should it stay above the level of the tank in the fender well? http://www.yogisinc.com/Detail.cfm/-...vv/product.htm

09-29-2009, 02:18 PM	#10
hotrodrookie Registered User Join Date: Sep 2008 Location: Sacramento Posts: 425	Re: Gas tank vent? I dont mean to hijack, but the reason I asked, is im gona run a pump similar to the tanks inc pump and I figured I should vent the tank. The screw in tank vent stops fuel from pouring out if ever turned over but mainly serves as a vent for fumes to exit the tank. Any info on routing the vent tube?



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