how much do the fuel tanks hold on a 74 f-100 long box. I have not had my truck too terribly long and i don't know how much to trust the fuel gauge. i topped it off when i bought it and i haven't kept track of millage but iv done a fair bit of driving in it. and it was down to 1/4 tank on the gauge so i filled it up to my surprise about 10 gallons filled it back up. so are these tanks really that small or is my gauge reading lower than it should be?

 

I was thinking the same thing. Why would they have such small tanks?

 

You'll have to read the fuel gauge with more skepticism. They are inherently inaccurate. My old '76 used to read fast the first half tank and then it slowed to a crawl.

I decided to replace the sender and discovered the resistor windings against which the float arm "wiped" against were all bunched at the bottom and really spread far apart near the top. The uneven distribution of the windings was causing the grossly inaccurate readings.

 

I agree mine is full at 7/8ths or so and then anything below 3/4 means it's,,,less then full. When it starts sputtering means it's probably empty regardless of what the gauge may say. To answer the question single tank in the rear should be around 19 gallons

 

To answer the OP's question, the main tank is 19.5 gallons.

 

thank you. knowing the capacity of the fuel tank really helps, then over time i can re-fuel at different gauge readings to look for consistency of fuel gauge to actual remains of fuel in the tank.