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Old 05-22-2023, 04:35 PM   #1
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fuel tank specs

have a 78 Silverado duel tank truck. I have always thought the capacity of each tank was 16 gallons. if my assumption is correct is the bottom of the tank larger than the top. It seems the first 1/2 of tank seems to fall alot faster then the second or is the tank less than 16 gals? Today when I filled up I was below 1/4 it would only take 10 gallons. Or are theses gauges not that accurate?

short bed

Last edited by kglowacky; 05-22-2023 at 04:59 PM.
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Old 05-22-2023, 04:54 PM   #2
Dead Parrot
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Re: fuel tank specs

Normal is short bed = 16, long bed = 20. The senders are NOT linear and the gauges vary from gauge to gauge. My normal is the gauge reads full until about 4 gallons are burned off, then it falls reasonably linear until near empty when there will be about 4 gallons until the tank runs dry. 20 gallon tanks. There is a difference between the two tanks on how the gauge behaves.

Run one until it is empty, then fill it up, You will have your answer on capacity. Do make sure the other tank is full before this test.
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Old 05-23-2023, 05:18 PM   #3
406 Q-ship
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Re: fuel tank specs

These truck have notorious issue when filling up. They will get air locked the last 2 to 4 gallons and spit back out the neck when trying to fill them all the way to the top. My Dads new 1978 GMC C15 short bed fleetside used to be a pain in the arse to fill. My 1974 C10 step side short bed will take in 12 gallons then shut off and kick back, if I go slow at that point I can get maybe 2 more gallons in. Best I ever got it to take was when I lived in So Cal and a gas station was on a funky hill, truck tail was higher than the rest of the truck and it took all 30 gallons without a hitch.

I have had saddle tanks in my truck with a balance tube, I could fill both tanks at once and no need for switcher valve. I did fuel injection and replaced the right tank (went plastic) so my dual tanks went away. Here in Florida having the ability to travel very long distances without a refill wasn't as big of a deal.
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