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#1 |
Registered User
Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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68 to 72 Gas Tank swap... what is required?
I have a nice '72 gas tank (w/ EEC) and a horrible tank in my '68. I want to swap them and I have removed and cleaned up the '72 tank but the sender is shot. The sender on the '68 had been replaced so it works well, and I'm planning on using that.
I have a couple of questions though... - Why does the '72 sender have two lines coming out of it, and what improvement is that over the '68 design? - There is a "vapor line" on the passenger side of the '72 tank. Can I just plug that off or should I try to make it functional? - Do I need to get a '72 style fuel filler grommet and ditch my '68, and who makes the most durable grommet? - Where can I get a replacement sending unit filter sock thingy? TIA!
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1968 LWB C20 / AC / Wood Bed |
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#2 |
Registered User
Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
ttt
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1968 LWB C20 / AC / Wood Bed |
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#3 |
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Join Date: Jul 2010
Location: Whittier Ca
Posts: 172
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Re: 68 to 72 Gas Tank swap... what is required?
Good Question. I have a bad sending unit in my tank and need to get it fixed.
Any help is appreciated.
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Ed F 1972 Sierra Grande White Top Medium Olive 402 bb / Camper Stock, Loaded, Straight & Aged Nicely, No Tilt Original Resto would be nice $ ![]() |
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#4 |
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Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
Well, I measured the pickup tube, it is 3/8"... so a 3/8" filter should work. I saw some at http://www.truckandcarshop.com/6072.html for $9, but a new sending unit is only $24 so it would probably be worth it just to replace the whole thing.
I did some comparison of the sending units, and the main difference seems to be that the '72 has an extra outlet the only extends a couple of inches into the gas tank. I can't tell by my catalogs where this line actually goes, but I am certain that it could just be plugged off with no ill effects. In that sense, it may be more "future proof" to get a 72 style sending unit and cap it off in case I want to add whatever that is for in the future.
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1968 LWB C20 / AC / Wood Bed |
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#5 |
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Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
I'm going to go with the 68-style sender, but out of curiosity does anyone know what the difference is between the manual trans and auto trans senders for '72?
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1968 LWB C20 / AC / Wood Bed |
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#6 |
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Join Date: Jul 2010
Location: Whittier Ca
Posts: 172
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Re: 68 to 72 Gas Tank swap... what is required?
Good question.
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Ed F 1972 Sierra Grande White Top Medium Olive 402 bb / Camper Stock, Loaded, Straight & Aged Nicely, No Tilt Original Resto would be nice $ ![]() |
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#7 |
Account Suspended
Join Date: Sep 2010
Location: hingham ma
Posts: 1,721
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Re: 68 to 72 Gas Tank swap... what is required?
the extra line on the 72 is to the charcoal can.. I'd not "just plug it) or you'll get a nice pressurized tank behind you.. and a very dangerous issue when you take the cap off to fill.
the 72 sender with vent to the charcoal can will be a better choice as the "closed system" will afford the gas to last longer.. in the summer heat. it just evaporates, and also todays fuel has ethinol(sp?) in it 10% and they are moving to 15% it absorbs water an open system (just a vent) will only add to the water being absorbed by the fuel.. and you'll have an issue later as the water sits on top of the fuel in the tank..and builds and builds and, then you have a truck try'n to run on water.. I'd rethink that 68 sender |
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#8 |
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Join Date: Sep 2006
Location: Bellwood, PA
Posts: 123
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Re: 68 to 72 Gas Tank swap... what is required?
Water sinks to the bottom of the tank, not the top. Water is more dense than gasoline.
Personally, I would use the 68 sender, leave the upper vent hose IF you are using the cap from the 72 tank, and just run it. Last edited by w3lfd; 10-20-2010 at 08:19 AM. |
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#9 |
Registered User
Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
Why would I get a pressurized tank? The '72 sender with the vent outlet plugged should be functionally identical to the '68 sender, and '68 tanks don't get pressurized, do they?
I do have to use a '72 cap since I have a '72 filler neck. Is the upper vent hose the one that comes off the passenger side of the tank and runs up into the cab corner?
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1968 LWB C20 / AC / Wood Bed Last edited by crakarjax; 10-20-2010 at 09:37 AM. |
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#10 |
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Join Date: Sep 2010
Location: hingham ma
Posts: 1,721
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Re: 68 to 72 Gas Tank swap... what is required?
forgot about the upper corner vent..
and water to the bottom.. it was early.. water and steel = rust |
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#11 |
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Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
So you are saying the 68 sender is better because it has no vent and thus doesn't allow water to be absorbed by the gas?
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1968 LWB C20 / AC / Wood Bed |
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#12 | |
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Join Date: Sep 2010
Location: hingham ma
Posts: 1,721
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Re: 68 to 72 Gas Tank swap... what is required?
Quote:
is with todays fuels I'd want a sealed system with a charcoal can alky evaporates, and absorbs water, when the alky evaporates the water stays and doesn't mix with the gas.. not an issue if you drive it daily, but if it sits.. |
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#13 |
Registered User
![]() Join Date: Apr 2010
Location: Holmen, WI
Posts: 212
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Re: 68 to 72 Gas Tank swap... what is required?
Get the 68 sending unit. Cap off the vent that goes up into the corner and put on a vented gas cap. Everything will vent through the gas cap and you can buy them at carquest and napa.
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ROD ![]() 1969 K10 4x4 Short Fleet. Tuned Port Injection 350/700R4, Cruise, tilt and factory A/C. 1971 C20 Camper Special. 350/350. SOLD 2002 Chevy Tahoe LT |
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#14 |
Registered User
Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
Do you by chance know the vehicle application for the vented cap that fits on a '72 tank? I read up on vented/non-vented applications and I think that if I cannot find a vented cap, then I need to run a vent line to a canister to avoid negative pressure in the tank! That means that I'll have to punch a hole in the floor, and I really don't want to do that.
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1968 LWB C20 / AC / Wood Bed Last edited by crakarjax; 10-20-2010 at 03:37 PM. |
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#15 |
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Join Date: Mar 2003
Location: San Francisco, CA USA
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Re: 68 to 72 Gas Tank swap... what is required?
This thread appears to concern the same issue.
http://67-72chevytrucks.com/vboard/s...d.php?t=426566 Ray Last edited by raycow; 10-20-2010 at 08:33 PM. |
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#16 | |
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Join Date: Dec 2009
Location: Kirkland, WA
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Re: 68 to 72 Gas Tank swap... what is required?
Quote:
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#17 |
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Join Date: Dec 2009
Location: Kirkland, WA
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Re: 68 to 72 Gas Tank swap... what is required?
^^ Also, I still haven't heard anyone's take on the '72 vs '68 style fill neck grommet!
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1968 LWB C20 / AC / Wood Bed |
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#18 |
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Join Date: Dec 2009
Location: Kirkland, WA
Posts: 1,302
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Re: 68 to 72 Gas Tank swap... what is required?
Finally found someone noting that the 67-70 necks are slightly larger, so I'll be going with the 71-72 style grommet to match the neck.
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