Fuel tank vent question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

suburban99 · 09-02-2017, 12:40 AM

Got my 1972 K10 LQ4 swap running good. Stock tank with a walbro and stock return line. Now I need to vent the tank or get a vented cap...The 72's have a non vented cap from the factory, and my tank gets a little pressurized after a short drive. What have others done that has worked?

**mongocanfly** · 09-02-2017, 12:49 AM

yep...your gonna need a vent..I can't remember how a 72 tank is but I would have thought it'd had a vent of some sort...at least get a vented cap..

suburban99 · 09-02-2017, 12:51 AM

Quote:

Originally Posted by mongocanfly

yep...your gonna need a vent..I can't remember how a 72 tank is but I would have thought it'd had a vent of some sort...at least get a vented cap..

Relatively sure it had a charcoal canister under the hood. But not since I have owned it.

**mongocanfly** · 09-02-2017, 12:57 AM

http://67-72chevytrucks.com/vboard/s...d.php?t=652299

**mongocanfly** · 09-02-2017, 12:59 AM

also found this on another site....

The 2 that I have had, ('72s) there was a line coming off of the passenger side of the tank that hooks to a loop up inside the cab beside the rear window. It's between the inner and outer walls. This is connected to a line that went to thecharcoal*canister*up in the inside if the front fender. (Right side, IIRC) then that was connected to the carb. I think, but I can't remember for sure, that the earlier trucks had a vented cap and the '72 wasn't. I don't remember for sure..The problem with the vented cap is that it is one more way for gas to spill down the side of the cab when it doesn't hold. The gasket on the cap has a hard time sealing against a full tank sloshing anyway. So if your cap is holding that well, look at the*vent*lines. The loop up in the cab makes sense to me, but it may not do as much as I think. ..?

suburban99 · 09-02-2017, 10:16 AM

I connected my return line to the line that ran to the charcoal canister..I guess..
The canister was long gone when I got her.
Does this look like a vented cap? It's got some kind of a valve built in..

suburban99 · 09-02-2017, 10:21 AM

Ok what's pressure vacuum ?

**mongocanfly** · 09-02-2017, 01:41 PM

http://forums.aaca.org/topic/231394-...dentification/

**mongocanfly** · 09-02-2017, 01:42 PM

http://stant.com/index.php/english/p...tion-fuel-cap/

09-02-2017, 12:40 AM	#1
suburban99 Registered User Join Date: May 2014 Location: Mission BC Posts: 452	Fuel tank vent question Got my 1972 K10 LQ4 swap running good. Stock tank with a walbro and stock return line. Now I need to vent the tank or get a vented cap...The 72's have a non vented cap from the factory, and my tank gets a little pressurized after a short drive. What have others done that has worked? __________________ 1962 C10 Longbox LS 5.3 4L60E----Sold$$ 2014 Ram 4x4 3500 Laramie Diesel..Momma's truck 2015 Ram 4x4 1500 1997 Boxster. 1972 K10 Custom Deluxe LS 6.0 1950 GMC 3100 S10 & LS swapped

09-02-2017, 12:49 AM	#2
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: Fuel tank vent question yep...your gonna need a vent..I can't remember how a 72 tank is but I would have thought it'd had a vent of some sort...at least get a vented cap..

09-02-2017, 12:57 AM	#4
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: Fuel tank vent question http://67-72chevytrucks.com/vboard/s...d.php?t=652299

09-02-2017, 12:59 AM	#5
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: Fuel tank vent question also found this on another site.... The 2 that I have had, ('72s) there was a line coming off of the passenger side of the tank that hooks to a loop up inside the cab beside the rear window. It's between the inner and outer walls. This is connected to a line that went to thecharcoalcanisterup in the inside if the front fender. (Right side, IIRC) then that was connected to the carb. I think, but I can't remember for sure, that the earlier trucks had a vented cap and the '72 wasn't. I don't remember for sure..The problem with the vented cap is that it is one more way for gas to spill down the side of the cab when it doesn't hold. The gasket on the cap has a hard time sealing against a full tank sloshing anyway. So if your cap is holding that well, look at theventlines. The loop up in the cab makes sense to me, but it may not do as much as I think. ..?

09-02-2017, 10:16 AM	#6
suburban99 Registered User Join Date: May 2014 Location: Mission BC Posts: 452	Re: Fuel tank vent question I connected my return line to the line that ran to the charcoal canister..I guess.. The canister was long gone when I got her. Does this look like a vented cap? It's got some kind of a valve built in.. Attached Images __________________ 1962 C10 Longbox LS 5.3 4L60E----Sold$$ 2014 Ram 4x4 3500 Laramie Diesel..Momma's truck 2015 Ram 4x4 1500 1997 Boxster. 1972 K10 Custom Deluxe LS 6.0 1950 GMC 3100 S10 & LS swapped

09-02-2017, 10:21 AM	#7
suburban99 Registered User Join Date: May 2014 Location: Mission BC Posts: 452	Re: Fuel tank vent question Ok what's pressure vacuum ? Attached Images __________________ 1962 C10 Longbox LS 5.3 4L60E----Sold$$ 2014 Ram 4x4 3500 Laramie Diesel..Momma's truck 2015 Ram 4x4 1500 1997 Boxster. 1972 K10 Custom Deluxe LS 6.0 1950 GMC 3100 S10 & LS swapped

09-02-2017, 01:41 PM	#8
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: Fuel tank vent question http://forums.aaca.org/topic/231394-...dentification/

09-02-2017, 01:42 PM	#9
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: Fuel tank vent question http://stant.com/index.php/english/p...tion-fuel-cap/

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