ronarndt

I'm having a perplexing problem with my 68 convert. It left the factory as a 327 car, but the PO transplanted a 454. I'm assuming he did not change the gas tank, so it should be a 17 gal tank, not the 20 gal ones for the HP BB cars. When I fill the tank, with about 2 inches of fuel left, I can only squeeze 10 gal to fill it. This gives me the impression the tank holds less than 17 gal, since 7 gal left in the tank should be deeper than 2 inches. Or am I missing something. .... Guess I could let it go bone dry and measure it. Either way, long trips need a lot of fill-ups.

Alan 71

Hi r,
There was just one sized gas tank used for 68-72 cars.
It had a 20 gallon capacity regardless of what engine the car was equipped with.

Has the original tank in your car been replaced with something else?
Regards,
Alan

theandies

I'm trying to nail down the same problem. I did replace my tank a while back but it was the same size as the original. I also replaced my sending unit so the ohm values may be off. With my gauge reading empty my sending unit is reading 10 ohms which by my calculation should be an 1/8 of a tank if my tank can hold 18 gallons as original.
Check out my thread on this topic:

Ohm readings for fuel level sender unit.

Hammerhead Fred

All my documentation (and hundreds of fill-ups) indicate something less than 18 gallons for 71/72.
Where are you finding 20 gallons for 71-72?
68-69 were 20 and 1970 was 18 or 20 depending on how you read the parts illustration guide

ronarndt

Alan- I cannot see evidence it was changed. The PO made changes that usually were easy to see. If it is supposed to be a 20 gallon tank, that makes this more puzzling. I may have to completely drain the tank and then measure how much is required to fill it. I keep a log book of every fill up and never had anywhere near a 18-20 gallon fill.
RA

riverracer au

i just had a look at the Vehicle information kits downloads
https://gmheritagecenter.com/gm-heri...tion-kits.html

last few pages with all the specs have the following listed:

the 68 had a 20us gallon tank, 327 & 427
my 72 has a 18us gallon tank, 350, lt1 & 454

i wish there was a larger capacity tank for mine, i do long cross country drives occasionally.

CanadaGrant

My 69 owners manual says "approx 20 US gallons" for all.

Alan 71

Hi HFred,
I'm away from home so don't have my 'stuff' with me.
So I looked at the Quanta Tank site and saw they list 20 gallons capacity for the various 68-72 tanks.
This morning I just looked at the Chevrolet Heritage site and the fuel capacity for 71 is listed at "18 Gallons (Approximate)".
Perhaps the 'Evaporative Emissions Control' changes to the tank that began in 70/71 limited how much gas could effectively be put in the tank under actual operating conditions?
Regards,
Alan

Is it the position of this 'pipe' that limits the effective capacity of the tank?

Clams Canino

For what it's worth, I know I can put almost two gallons in my '68 after it appears full.
This by pumping slowly and watching the bubbles come out.
-W

MelWff

to anybody who thinks their tank is not holding what it should hold, check if the tank has collapsed. You may need to drop the spare tire carrier for a good look at the bottom. Another tell tale sign is if the gas cap neck doesn't appear to be properly aligned with the gas door.