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Doc68 01-02-2004 11:58 AM

Fuel Tank Installation Plumbing Questions
 
I have a '28 Ford rat rod that came with a small fuel tank in the trunk (10 gal). I drive a lot and fueling up every 200 miles became a drag real fast. I debated installing a larger tank, but when it came to cost, it was way less expensive to install a secondary tank (I had room in the trunk).

I am about to install the second tank (11 gal). I'm going to run a line from that tank to a T. The original fuel tank will also go to the T. The T will, of course, exit to the main fuel line to the engine. I do not want to install a second fuel gauge sender (the one works fine on the original tank).

I've talked to several people and I am receiving conflicting information regarding the position/placement of the second tank for the above configuration to work. Some have said the tanks have got to be parallel with the bottom halves of each tank (where the fuel exits the tank) to be level with each other, otherwise air will get into the system. Others have said that the fill tubes have to be approximately the same height or fuel will attempt to run from one tank to another, causing fueling problems. Still others are concerned about venting (both tanks come with a vented fuel cap) and the impact on both fueling and air. My fuel pump is mechanical.

Has anyone set up a system similar to what I suggest? That is, just running to fuel lines to a standard T so fuel is drawn equally from both tanks. Am I missing anything? Something I need to know before proceeding? Any help would be appreciated.

Frisco 01-03-2004 01:13 PM

Because liquid will seek to be level; the bottom of both tanks will have to be mounted at the same height. The top of the tanks should be the same height of each other or you will only be able to fill the lower height tank. This is because the fuel will run from one tank to the other and as one tank is (for example) filled 4 " from the bottom so will the second tank. The vented caps should be fine.

Your working fuel gauge will read OK, but remember that when it reads 1/2 you will have half in one tank and half in the other.

Using a 10 gallon tank and an 11 gallon tank will not enable you to have a total of 21 gallons unless the tanks are both the same height.

4 Jaw Chuck 01-03-2004 02:08 PM

I would look into finding a non-vented cap for the lower tank and then use the top tank to feed the lower tank through the vent tube. Can you give us an idea which tanks your using? Having a large vent tube to feed between the two tanks is important or else you will find filling the both of them takes a long time (have to wait for the lower tank to catch up if your below half full). Safety lock-wiring the lower tank cap on is a good idea just in case.

The trick is finding a non-vented cap to fit your lower tank.;)

Doc68 01-03-2004 08:47 PM

The original tank came from Total Performance, made of steel, advertised to be used with T-buckets. It is rectangle.

The second tank is from Dan's (a Dune Buggy outfit), made of heavy duty Poly, and is cylindrical (10 inch by 33 inch).

Neither tank has a vent tube, so both tanks would have to be drilled and a tube run. Frankly, I don't want to do that unless it's absolutely necessary.

Because of the size and shape of the tanks, I can match the bottom or I can match the top, but I can't do both. Which is better for faster filling and/or for total fuel capacity?

Another option mentioned by a friend would be to run a fuel switch between the two. Run one tank then the other so I would not have to worry about the height of the tanks. Advantages/disadvantages of that option?

4 Jaw Chuck 01-03-2004 09:53 PM

I would run a switch for all the hassle, many trucks use them and finding new parts should be easy. Would be nice to wire in a new sender for the other tank so when you switch you get the new tanks fuel level.

Thats the way I would go.

Shortstep 01-04-2004 10:02 AM

I don't think the two tanks have to be same level as long as the tops are the same level and the T is below both tanks. One tank will run out first but this shouldn't be a problem. Or you could just do like on a motorcycle and have a spare tank. Put a valve for the tank with a gauge and cut it off until you run out or nearly out and then go to the reserve tank. Of course this is a little risky in traffic so you might want to plumb it for easy access.

poncho62 01-04-2004 10:13 AM

I don't think its worth all the hassle, plus the safety factor. I have a 20 gallon tank, and still have to fill up every 200 miles. If I was getting 20 mpg, I would be happy to gas up every 200 miles.

Doc68 01-04-2004 05:43 PM

I can sympathize with Poncho's point of view. My 283 is very fuel thrifty for all the punch it gives, but I would be filling up every three days. My Rat is used as a daily driver. Plus in California, long distances to car shows is the norm. Try driving 600 plus miles round trip to a meet and fill ups become a pain in the butt.

Safety should not be an issue with a fuel selector switch. You'd never want to drain the tank dry anyway. Look at the trip meter and when 200 miles rolls around switch to the tank that has the gauge. Sure, you never use all of the 21 gallons but I wouldn't want to do that in any case. Not much to it.

Shortstep's comment is an interesting one. However, I think it will be easier to have the one tank lower than the other from an installation point of view. Using a fuel tank selector switch, although not my first choice, seems to be the way to go to avoid all the issues of fuel levels, heights, etc.

T5Bird 01-04-2004 08:24 PM

Quote:

Originally posted by 4 Jaw Chuck
I would run a switch for all the hassle, many trucks use them and finding new parts should be easy. Would be nice to wire in a new sender for the other tank so when you switch you get the new tanks fuel level.

Thats the way I would go.

Yes Pollak makes a 3 port fuel solenoid that would work great, basically the same as 70's and 80's GM trucks. But yes a sending unit would be nice.

Doc68 01-05-2004 06:20 PM

I purchased a fuel selector valve and switch at Autozone today. Cheap, cheap!! Paid $31 bucks total. Exactly what I want. Got the rest of the plumbing hardware and will put it together tomorrow. Will let everyone know how it works.


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