I need to vent................ - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mobileortho · 01-10-2009, 09:05 PM

Or do I? I'm trying to determine if I need to run a vent line to my underbed tank. I went with the bed fill spout and the illustrations I've seen show the spout attached directly to the tank via a short hose, but there is no provision on the spout itself for the vent as it is on the stock unit. Is there another way to run a vent line or is it really necessary? There is also an additional outlet on the opposite side of the tank that I don't know what its used for. Someone suggested that it was there to relieve pressure buildup, but how do you go about doing that?

CAL 58 GMC · 01-11-2009, 01:14 PM

You definitely need to run a vent line. It's like drinking out of a plastic water bottle with your mouth sealed around the rim as you suck water into your mouth, the bottle starts to collapse and water gets harder to suck out. The fuel will flow alot better with a vent.

OrrieG · 01-11-2009, 03:02 PM

If you are running conventional carb with stock engine mounted fuel pump you need a vent. Like Cal said without it and an unvented cap you get a vaccum in the tank. Also no pressure relief when filling. I don't know anything about modern injected engines with the fuel pumps in the engines. My after market tank came with a threaded hole for attaching a 3/8" hose fitting. I a using the stock filler relocated to the bed side so that is where the vent will go. You can get aftermarket fillers from marine suppliers that have the vent line configuration too. Some guys just run the hose higher than the tank and put in a check valve. Search some of the build threads using "gas tank" as a search word and you will find an bunch of different ideas with manf. info or links to suppliers.

mobileortho · 01-11-2009, 10:26 PM

OK, I think I figured it out. I found this vent tube off of a late model fuel spout. It has a a cap on the end that allows pressure to bleed off as needed. Is it ok for me to mount it on the spout as shown and run the other end to the opposite side of the tank?

Atomsplitter · 01-12-2009, 11:40 AM

My motor is fuel injected and has a return line but I vented it anyway. I ran my vent line up the inside of the rear fender about a foot and back down. This was my only choice as my tank sits alot higher than yours and I wanted the vent well above the full level in the tank, where did you get the "one way" vent fitting from?

entourageguy · 01-12-2009, 02:41 PM

I've seen the one way fitting from compa ies like russell that make the an type fittings.

**mr48chev** · 01-12-2009, 04:41 PM

I'd run a vent similar to what Atomsplitter said he has on his truck. You might run a line over to one of the posts(bed corners) and run it up inside it with some type of vent cap on it. Out of the way and high enough so that it wouldn't bleed over if the fuel expanded in the tank on a hot day.
It's not rocket science, you just need to be able to vent the tank and have the vent high enough so that you don't create a leak when the tank is full.

mobileortho · 01-12-2009, 05:35 PM

Quote:

Originally Posted by Atomsplitter

where did you get the "one way" vent fitting from?

I believe it came off of a late model chevy truck. I picked it up at a local body shop that was about to trash it.

mobileortho · 01-17-2009, 09:18 PM

I talked to the guys at Tanks Inc. and they suggested that I use this rollover vent valve. It will vent the tank and also seal itself off in case of a rollever. I mounted it in the right rear stake pocket, ran the hose through the frame then to the tank. I'm not sure if moisture will be able to get in so I'll eventually get some covers for the opening.

01-10-2009, 09:05 PM	#1
mobileortho Registered User Join Date: Sep 2008 Location: Hampton, VA Posts: 904	I need to vent................ Or do I? I'm trying to determine if I need to run a vent line to my underbed tank. I went with the bed fill spout and the illustrations I've seen show the spout attached directly to the tank via a short hose, but there is no provision on the spout itself for the vent as it is on the stock unit. Is there another way to run a vent line or is it really necessary? There is also an additional outlet on the opposite side of the tank that I don't know what its used for. Someone suggested that it was there to relieve pressure buildup, but how do you go about doing that? __________________ Robert C. 1950 3600 3600 re-do, shortening it up If it's true what they say, "You learn from your mistakes," I'm a Genius in the making. Last edited by mobileortho; 01-10-2009 at 09:26 PM.

01-11-2009, 01:14 PM	#2
CAL 58 GMC Senior Member Join Date: Jun 2005 Location: Clovis Ca. Posts: 3,311	Re: I need to vent................ You definitely need to run a vent line. It's like drinking out of a plastic water bottle with your mouth sealed around the rim as you suck water into your mouth, the bottle starts to collapse and water gets harder to suck out. The fuel will flow alot better with a vent. __________________ Classic Trucks Link http://www.classictrucks.com/feature...uck/index.html 1958 GMC.Project Build http://67-72chevytrucks.com/vboard/s...d.php?t=162816 1966 Chevelle Build http://67-72chevytrucks.com/vboard/s...d.php?t=443576 Video http://www.youtube.com/watch?v=prrNKo8F7Zw#GU5U2spHI_4

01-11-2009, 03:02 PM	#3
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: I need to vent................ If you are running conventional carb with stock engine mounted fuel pump you need a vent. Like Cal said without it and an unvented cap you get a vaccum in the tank. Also no pressure relief when filling. I don't know anything about modern injected engines with the fuel pumps in the engines. My after market tank came with a threaded hole for attaching a 3/8" hose fitting. I a using the stock filler relocated to the bed side so that is where the vent will go. You can get aftermarket fillers from marine suppliers that have the vent line configuration too. Some guys just run the hose higher than the tank and put in a check valve. Search some of the build threads using "gas tank" as a search word and you will find an bunch of different ideas with manf. info or links to suppliers. __________________ 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 Last edited by OrrieG; 01-11-2009 at 03:02 PM.

01-11-2009, 10:26 PM	#4
mobileortho Registered User Join Date: Sep 2008 Location: Hampton, VA Posts: 904	Re: I need to vent................ OK, I think I figured it out. I found this vent tube off of a late model fuel spout. It has a a cap on the end that allows pressure to bleed off as needed. Is it ok for me to mount it on the spout as shown and run the other end to the opposite side of the tank? __________________ Robert C. 1950 3600 3600 re-do, shortening it up If it's true what they say, "You learn from your mistakes," I'm a Genius in the making.

01-12-2009, 11:40 AM	#5
Atomsplitter Registered User Join Date: Mar 2006 Location: Ontario Posts: 514	Re: I need to vent................ My motor is fuel injected and has a return line but I vented it anyway. I ran my vent line up the inside of the rear fender about a foot and back down. This was my only choice as my tank sits alot higher than yours and I wanted the vent well above the full level in the tank, where did you get the "one way" vent fitting from?

01-12-2009, 02:41 PM	#6
entourageguy Yellow truck club Join Date: Apr 2006 Location: Barrie Ontario Posts: 2,080	Re: I need to vent................ I've seen the one way fitting from compa ies like russell that make the an type fittings. __________________ ................................................................ Brian ...... My hub garage address http://www.hubgarage.com/mygarage/59apache I gue$$ everything has it'$ price ALL GONE NOW *59 Chev Apache* *PRAISE THE LOWERED* 350 700r lokar shifter power MII front end, shockwaves tilt, 4 wheel discs 4-link and bags 10 bolt limited

01-12-2009, 04:41 PM	#7
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,711	Re: I need to vent................ I'd run a vent similar to what Atomsplitter said he has on his truck. You might run a line over to one of the posts(bed corners) and run it up inside it with some type of vent cap on it. Out of the way and high enough so that it wouldn't bleed over if the fuel expanded in the tank on a hot day. It's not rocket science, you just need to be able to vent the tank and have the vent high enough so that you don't create a leak when the tank is full.

01-17-2009, 09:18 PM	#9
mobileortho Registered User Join Date: Sep 2008 Location: Hampton, VA Posts: 904	Re: I need to vent................ I talked to the guys at Tanks Inc. and they suggested that I use this rollover vent valve. It will vent the tank and also seal itself off in case of a rollever. I mounted it in the right rear stake pocket, ran the hose through the frame then to the tank. I'm not sure if moisture will be able to get in so I'll eventually get some covers for the opening. __________________ Robert C. 1950 3600 3600 re-do, shortening it up If it's true what they say, "You learn from your mistakes," I'm a Genius in the making.



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