Factory Auxiliary Sub Tank Install

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I finally took the time to pay attention to the fuel transfer time. In the beginning I was thinking 10-12 mins but I only had done it at speed while driving. I was happy to find out it only takes 7 mins to dump 15 gals from my aux into my main, Holley Blue pump rock!
 
When you re-worked the tank did you enlarge it? In stock form they hold a little over 13 gallons. They do trick you into thinking they are close to 15 gallons when you fill them. The flapper does not close the main off fully and you will dump around two gallons into the main while the sub is filling.
 
cruiserdan said:
When you re-worked the tank did you enlarge it? In stock form they hold a little over 13 gallons. They do trick you into thinking they are close to 15 gallons when you fill them. The flapper does not close the main off fully and you will dump around two gallons into the main while the sub is filling.
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I just checked your theory having an extra used dual filler neck on the shelf and if I block off one of the fillers and pressurize it I get no leakage:meh: Same results on both fillers outlets. I cant believe the new one I installed would be any different. I see no other way I could get loss when filling the aux tank. My vent lines are not tied together either. I do not have any baffles(except pump basket), sending unit, or pumps inside but not likely adding up to 2 gals. I did bend the vent tube inside tank up as close to the top of the tank as posssible...maybe the answer:meh:

When I first installed it I determined before final plumbing I can pump out all but ~1 quart and I have consistently filled the aux with 14.5 - 14.75 gals after purging it.
 
Cool. My neck (later type) does not completely seal when it is pulled up to fill the sub. It takes, according to the gas pump, around 15 gallons to fill it. That can varry as much as a gallon and I always pump the sub dry.

My main low fuel light comes on with right at 5 gallons left. When I fill both tanks at that point it takes right at 33 gallons every time. The main is 25.1 gallons total so that makes the sub ~13 gallons, which it what the published capacity is in the OZ owner's manuals....:meh:
 
Curious how you cut the steel filler neck? Sawsall, hacksaw etc. I'm assuming you drained the main tank?
 
Phil I found the photo Ozcal sent me of his owner's manual:

IMG_5747[1].webp
 
Have you ever checked the 13 gal
gofast said:
Curious how you cut the steel filler neck? Sawsall, hacksaw etc. I'm assuming you drained the main tank?
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Didnt drain the main, actually I was told is would be safer (if that is possible) to do it full. Use a hacksaw for the main filler and the cut the main vent line twice for my feed line. IMO it was much more dangerous cutting a hole in the big hole in the tank to remove the baffles then grinding and welding it back up. :rolleyes: I will not be doing anymore gas tank work feeling my odds are getting lower for a problem.
 
cruiserdan said:
Phil I found the photo Ozcal sent me of his owner's manual:

View attachment 1008390
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Just info, not my experience, would not be the first time info was wrong. The HP on my 70 LS6 was rated at 450 also

Maybe your filler neck doesnt leak like you were led to believe;)
 
I watched the main gas gauge rise a bit as I filled the sub......:)
 
Do you always fill the sub first? If so try filling the main first and then see what it takes to fill the sub. When I did that the sub took ~13 gallons...
 
cruiserdan said:
I watched the main gas gauge rise a bit as I filled the sub......:)[/QUOTE}

Fact are fact sorry
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cruiserdan said:
Do you always fill the sub first? If so try filling the main first and then see what it takes to fill the sub. When I did that the sub took ~13 gallons...
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The main was full (see post #47) when I filled it the first time:grinpimp:

If it makes you feel better like I said prior, I bent the vent tube inside the tank up to the top of the tank.
 
Fair enough.
 
cruiserdan said:
Fair enough.
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The vent does not have a flapper like the main filler neck and the main flapper is not springed just hangs there and would do a poor job of sealing. I have also read if you have the angled filler neck you are not able to get the same amount of gas in. Is your filler neck outlets angled or horizontal?
 
Mine is the later version, as used in 96-97.
Picture 007.webp
 
Picture 016.webp
 
Interesting. Maybe mine is jacked internally.
 
Agreed.

Now what I have not done is pull the drain plugs on both tanks to empty them completely and then fill them both up to see what really goes in.


I'm gonna have to do that one day.
 
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