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#1 |
Vintage 4x4s
Join Date: Sep 2010
Location: Prior Lake, MN
Posts: 4,305
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Which trucks had vent lines on the gas tank?
Seems like none of the trucks around here have it. (based on a few 67's to 71's I have sitting here) but I was reading about these on the board.
Also, at least one replacement tank LMC sells has the vent ports. Thoughts?
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67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ![]() 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6 |
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#2 |
Registered User
![]() Join Date: Jul 2012
Location: Deer Park, Tx
Posts: 107
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Re: Which trucks had vent lines on the gas tank?
1972 had vent
Posted via Mobile Device
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All Day Every Day '72 C20 Cheyenne Custom Camper http://67-72chevytrucks.com/vboard/s...d.php?t=549132 |
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#3 |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,682
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Re: Which trucks had vent lines on the gas tank?
My '70 has vented tank & charcoal canister. Even in 1970, General Motors was doing its part to keep us Californians breathing clean air.
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#4 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: Which trucks had vent lines on the gas tank?
I brought this topic up a while back, and someone informed me that 3/4 tons did not have vent lines.
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71 K20 64 GMC mud truck |
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#5 |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,682
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Re: Which trucks had vent lines on the gas tank?
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#6 |
Registered User
![]() Join Date: Jan 2012
Location: Whitesboro, Texas
Posts: 932
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Re: Which trucks had vent lines on the gas tank?
Interesting - My 72 GMC 2500 4x4 does not have vent lines.
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Cheers - Wayne Our Shop Build - http://67-72chevytrucks.com/vboard/s...d.php?t=620966 '55 Wagon Build - http://67-72chevytrucks.com/vboard/s...d.php?t=689157 1971 Cheyenne Super Ochre/White LWB 350 Auto - my son's truck "Nancy" 1972 GMC K2500 Custom 4X4 Olive LWB 400 SB 4-speed -"Greenie" - Restoration to begin after the '55 Nothing sucks more than that moment during an argument when you realize you're wrong. |
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#7 |
Registered User
Join Date: Mar 2011
Location: Brandon,Iowa
Posts: 391
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Re: Which trucks had vent lines on the gas tank?
None of my 3/4 ton trucks have vent lines. 3-'72's and a '71.
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#8 |
Senior Member
![]() Join Date: Feb 2001
Location: New Madison, Ohio
Posts: 21,365
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Re: Which trucks had vent lines on the gas tank?
I am signed on
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A husband can be right...or...A husband can be happy. ![]() 67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk. ![]() 1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc ![]() ![]() JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder! |
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#9 |
Registered User
Join Date: Sep 2012
Location: Queen Creek, AZ
Posts: 551
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Re: Which trucks had vent lines on the gas tank?
My 69 has a non vented original tank. I was told the 67-69 were non vent and 70-72 were vented.
Weev- Posted via Mobile Device
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Weev- Life's tough...... It's even tougher when your stupid - John Wayne |
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#10 |
Registered User
Join Date: Oct 2012
Location: Knoxville Tn
Posts: 47
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Re: Which trucks had vent lines on the gas tank?
I'm interested in knowing how to tell or how to fix my awesome fountain of gas spray I get every time I open my fuel cap... my flat black paint doesn't like the gas spray that well
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#11 |
Vintage 4x4s
Join Date: Sep 2010
Location: Prior Lake, MN
Posts: 4,305
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Re: Which trucks had vent lines on the gas tank?
Buy a vented cap assuming you don't have vent lines. Your system should not build pressure.
__________________
67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ![]() 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6 |
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#12 |
Registered User
Join Date: Sep 2010
Location: Jacksonville, NC
Posts: 596
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Re: Which trucks had vent lines on the gas tank?
It looks like I ordered the wrong tank if non of the 3/4 tons had vent lines. So can you run a vented tank with the vent line plugged? Would this hurt anything?
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"Some people spend an entire lifetime wondering if they've made a difference. The Marines don't have that problem." President Ronald Reagan,1985 "The Marines I have seen around the world have the cleanest bodies, the filthiest minds, the highest morale, and the lowest morals of any group of animals I have ever seen. Thank God for the United States Marine Corps!" ..............Eleanor Roosevelt, 1945 |
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#13 | ||
Vintage 4x4s
Join Date: Sep 2010
Location: Prior Lake, MN
Posts: 4,305
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Re: Which trucks had vent lines on the gas tank?
Quote:
Quote:
Tony, Capping the lines should not be a problem but its up to you. Jud
__________________
67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ![]() 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6 |
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#14 |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,682
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Re: Which trucks had vent lines on the gas tank?
[QUOTE=Vintage Windmills;5705837]Perhaps they changed in mid 1970 since I have a very original C/10 1970 parts truck with no vent lines.
I'm thinking it must be a state by state emission thing for the C-10's ? My SPID on the '70 shows "option NA9, Evap Emission Cntrl". Maybe all C-10's made at the Fremont plant in 1970 had a non-vented tank. I find it laughable that California put emission stuff on the C-10 yet nothing on the C-20, but both share the same engine. Now that i think about, that's not the only thing laughable that my state has done! ![]() |
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#15 |
Registered User
Join Date: Sep 2010
Location: Jacksonville, NC
Posts: 596
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Re: Which trucks had vent lines on the gas tank?
I say cap the vent line Mr. Jud, just let me know if I need to send another fuel cap or not.
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"Some people spend an entire lifetime wondering if they've made a difference. The Marines don't have that problem." President Ronald Reagan,1985 "The Marines I have seen around the world have the cleanest bodies, the filthiest minds, the highest morale, and the lowest morals of any group of animals I have ever seen. Thank God for the United States Marine Corps!" ..............Eleanor Roosevelt, 1945 |
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#16 |
"Ochre Ogre"
Join Date: Apr 2000
Location: Springfield, MN
Posts: 3,558
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Re: Which trucks had vent lines on the gas tank?
Of the things I have read over the years half ton trucks were considered to be light duty and had similar emissions devices as the cars. 3/4 ton and heavier trucks were considered heavy duty work trucks and were exempt from emissions add-ons like vents, TSC(transmission spark control devices, air injector pumps, and charcoal canisters.
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Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087 |
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#17 |
Registered User
Join Date: May 2012
Location: Atlanta, GA
Posts: 34
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Re: Which trucks had vent lines on the gas tank?
So did all C20's and above have vented gas caps? I have a 72 C10 built at the Fremont plant and the emission system is long gone. The vents are wide open under the truck and need to be cleaned up. If I cap off the vents and get a vented gas cap I should be good to go....just like the C20's and above were back in the day?
I certainly don't need pressure issues. Thanks all,
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72 C10 Deluxe Medium Blue/White 350/350 |
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#18 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: Which trucks had vent lines on the gas tank?
Yes, you will need some form of ventilation if the emission crap is all gone.
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71 K20 64 GMC mud truck |
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#19 |
Registered User
Join Date: May 2012
Location: Atlanta, GA
Posts: 34
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Re: Which trucks had vent lines on the gas tank?
Thanks 71K20 -
Do the caps have the ability to vent each direction to keep the pressure in the tank stable?
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72 C10 Deluxe Medium Blue/White 350/350 |
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#20 |
Registered User
Join Date: Sep 2012
Location: San Antonio, TX
Posts: 1,026
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Re: Which trucks had vent lines on the gas tank?
My 72 has the lines and they go up the passenger side pillar. I'm assuming that's what they are for the vent
Posted via Mobile Device
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Jeff 1972 Cheyenne Super SWB 350, Auto, Bucket Seats w/Console, Tach, Factory A/C, P/S ,P/B, Tilt 1998 Chevy 1500 Ext Cab 5.7, Pewter w/blue interior |
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#21 |
Registered User
Join Date: Jun 2012
Posts: 1,089
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Re: Which trucks had vent lines on the gas tank?
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#22 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: Which trucks had vent lines on the gas tank?
Which brings me to a question, in general, what psi do they begin to vent? Sometimes on my vented cap there's some pressure (sometimes vacuum while driving or in the winter months), not a lot, but it's there.
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71 K20 64 GMC mud truck |
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#23 |
Registered User
Join Date: May 2012
Location: Atlanta, GA
Posts: 34
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Re: Which trucks had vent lines on the gas tank?
71K20,
I just found this bit of info about the PSI range. Now I need to find the proper vented fuel cap for my 72 truck...since my canister is gone. Hope this helps.... The fuel cap contains an integral pressure and vacuum relief valve. The vacuum valve acts to allow air into the fuel tank to replace the fuel as it is used, while preventing vapors from escaping the tank through the atmosphere. The vacuum relief valve opens after a vacuum of -0.5 psi. The pressure valve acts as a backup pressure relief valve in the event the normal venting system is overcome by excessive generation of internal pressure or restriction of the normal venting system. The pressure relief range is 1.6-2.1 psi over atmospheric pressure. Fill cap damage or contamination that stops the pressure vacuum valve from working may result in deformation of the fuel tank.
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72 C10 Deluxe Medium Blue/White 350/350 |
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#24 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: Which trucks had vent lines on the gas tank?
Thanks for the info, answers my question!
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71 K20 64 GMC mud truck |
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#25 |
Registered User
Join Date: Aug 2012
Location: Midland, TX
Posts: 1,267
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Re: Which trucks had vent lines on the gas tank?
So, can someone clarify for me, what gas cap to use on a 72? The truck is as it came from the factory. Vented or non-vented?
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1969 RS/SS Z10 Camaro Pace coupe 1972 GMC Short Step buildhttp://67-72chevytrucks.com/vboard/s...=1#post6356218 1979 Mazda RX7 1979 Pontiac Trans Am WS6 & 1979 Pontiac Trans Am 10th Anniversary 1999 Honda Valkyrie 2006 Corvette Z06 2010 BMW 650i |
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