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Old 07-15-2011, 11:21 PM   #1
c10crazy
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How many gallons of gas???

I know my gas gauge is not that accurate but how many gallons of gas does our 67-72 trucks hold???
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Old 07-15-2011, 11:25 PM   #2
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Re: How many gallons of gas???

Someone can correct me, but I believe the standard tank behind the seat is 21 gallons.

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Old 07-15-2011, 11:30 PM   #3
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Re: How many gallons of gas???

That was the number that was in my head too! Tonight I was on a quarter tank and I filled it up with 9.5 gallons and the needle is almost a quarter past the full mark! That means when I'm showing a quarter tank it's almost a half tank! Do I have a bad gauge or sending unit???
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Old 07-15-2011, 11:35 PM   #4
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Re: How many gallons of gas???

behind the seat is 16 gallons, the aftermarket tanks that go between the frame rails are 20

Last edited by Fldawg; 07-15-2011 at 11:37 PM. Reason: forgot
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Old 07-15-2011, 11:54 PM   #5
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Re: How many gallons of gas???

i was under the assumption having the suicide tank was only 21 gal.... hmm i never even realized because i dont ever fill her up.

Last edited by elf w/capital T; 07-15-2011 at 11:54 PM. Reason: i was reading the post before me :hammer:
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Old 07-15-2011, 11:54 PM   #6
1968CHEVYC10
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Re: How many gallons of gas???

I've heard 20 for 1/2 tons and 21 for 3/4 ton+, I just filled mine from empty took 20 gal.
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Old 07-16-2011, 12:07 AM   #7
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Re: How many gallons of gas???

In the LMC catalog, the replacement tank behind the seat is 20 gallons and the Blazer tank is 21 gallons.


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Old 07-16-2011, 04:45 AM   #8
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Re: How many gallons of gas???

My 72 owners manual says 20 gallon capacity.
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Old 07-16-2011, 05:49 AM   #9
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Re: How many gallons of gas???

21 gallons. I've had them take over 20 gallons.
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Old 07-16-2011, 10:28 AM   #10
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Re: How many gallons of gas???

Tanks behind the seats apparently came in two different sizes... I believe 20+ gallon was most common.
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Old 07-16-2011, 11:07 AM   #11
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Re: How many gallons of gas???

Thanks for all the replies. I can't find my service manual that's why I posted. Now I have to determine if my gas gauge is the problem or my fuel sending unit. I'm guessing since they are both technically working (just not accurate) it's the gauge?
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Old 07-16-2011, 11:21 AM   #12
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Re: How many gallons of gas???

Quote:
Originally Posted by c10crazy View Post
I can't find my service manual
I know somebody here who has one
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Old 07-16-2011, 11:47 AM   #13
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Re: How many gallons of gas???

I can fit a little over 20 in mine from bone dry, but that is filling the neck also. I know, you're not supposed to do that since the cap is not vented, but when you get 14-15 mpg you want all the capacity you can get!!
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Old 07-16-2011, 12:30 PM   #14
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Re: How many gallons of gas???

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I know somebody here who has one
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Old 07-16-2011, 04:44 PM   #15
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Re: How many gallons of gas???

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My 72 owners manual says 20 gallon capacity.
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Quote:
Originally Posted by 70STOVEBOLT View Post
I can fit a little over 20 in mine from bone dry, but that is filling the neck also. I know, you're not supposed to do that since the cap is not vented, but when you get 14-15 mpg you want all the capacity you can get!!

Try 8.2 MPG. That's the highest I have got with my 383 so far. It likes tothough.
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Old 07-16-2011, 05:14 PM   #16
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Re: How many gallons of gas???

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Originally Posted by c10crazy View Post
Thanks for all the replies. I can't find my service manual that's why I posted. Now I have to determine if my gas gauge is the problem or my fuel sending unit. I'm guessing since they are both technically working (just not accurate) it's the gauge?
What does your gauge read now? If it is at 3 o'clock and stuck there, try grounding the sending unit post to a good ground. If the gauge goes to 9 o'clock, it is the sending unit that is bad. If the sender is working, the resistance should read between 0-90 ohms from the post to ground. Also make sure the wire from the sending unit post goes to the terminal on the fuse block that it is supposed to.

Mine turned out to be a bad sending unit - $30 later all was well.
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Old 07-16-2011, 06:02 PM   #17
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Re: How many gallons of gas???

pull the carpet sill on the drivers side and check the wire. I have found that it typically goes bad in this area.
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Old 07-18-2011, 08:40 AM   #18
70STOVEBOLT
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Re: How many gallons of gas???

What if it goes to about 2 o'clock when it is full and hits empty when it's got about a quarter of a tank left? Is there any way to "calibrate" the gauge? Mine works fine other than it seems to be off.
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Old 07-18-2011, 02:36 PM   #19
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Re: How many gallons of gas???

Again, 20 plus, but you are into the neck and it will slosh out. I have two saddle tanks two: one at 19 and the other around 12 gallons. With my 400, I would love to get 14 MPG. After all the carb work, I think I'm at 11 MPG and that's being easy on the pedal. Neither saddle tank is connected to the gauge. I run them out first and then switch to the main tank.
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Old 07-18-2011, 05:34 PM   #20
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Re: How many gallons of gas???

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Originally Posted by 70STOVEBOLT View Post
What if it goes to about 2 o'clock when it is full and hits empty when it's got about a quarter of a tank left? Is there any way to "calibrate" the gauge? Mine works fine other than it seems to be off.
You may have a leak in the brass float, it is probably half full gas and won't float to the top. Pull the sender out of the tank, it's held in with a lock ring. My 69 was doing the same thing, I went to the local NAPA parts store to get a new float and they had one in stock. The brass float simply clips into the float lever, easy fix!
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Old 07-18-2011, 06:32 PM   #21
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Re: How many gallons of gas???

well when gas was 1.00 a gallon back many moons ago back in 1989 my 1965 3/4 ton truck I could only get 16.00 into my tank so that mean's i have a 16 gallon tank and with a 350 with a 2 speed power glide with 4;10 gears running 235-85-16 tire's motor home 10 ply radials when there new I get 14 MPG with a 290 HP engine crate engine i run the smaller tires the 9.50 I can't get over 55 Mph with out it revving up past 4000 RPM's But buy running the 235-85-16 tall tire By 2 inches taller I changed my gearing by 377 But the power glide dose not help cus its a 2 speed But only had the power glide out 2 times do to seals and i have over 2 million Miles on the truck.From 1991 i put over 890K miles on this truck before that it use to be a long haul truck for UCR collage orange groves In Calif more of less SUNKIST oranges
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