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Old 11-16-2010, 05:18 PM
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How to Plumb Gas line to tank w/ 1/2"

Okay what I have done was order a 1/2" hard fuel line that runs from the tank to the engine (runs just like factory line ordered from inlinetube). My question is how do I connect it to the gas tank since the line coming out of the tank is 3/8. Do I pull the sending unit and try and re-plumb it with 1/2 line? Do I drill a hole in the bottom of the tank and run -8AN fitting from that?Whats a good fix here. If I drill a hole what type if fitting would I use? Someone has done this or knows how to fix this.

FYI at the engine I'm using the new HP Holley mechanical 175gph, and fitting it with -8AN to the pump then -8AN to the fuel log. My plan is to put a 100mic filter on the hard line before the pump then the fuel log I have had a 40 mic filter.

Thanks for the help.

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Old 11-16-2010, 05:44 PM
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You can get a new sending unit with 1/2" lines in the tank and a AN fitting to hook to coming out of the sender from RobbMC Performance if you want to go bolt-in. It is rather pricey though, $130

Most times for high performance use with a stock tank you would add a weld-on sump to the bottom rear section that has 2 or 3 outlets on it, Competition Engineering has one. Sump type is usually on street/strip and drag cars, to use the force of launch to ensure good feed into the line to the pump.

If you are the fabrication type, you could also equip you current sender with a 1/2" line into the tank in place of the 3/8", requires some soldering or brazing to complete.

Doesn't make much sense to hook a 1/2" line to a 3/8" pick-up, so I wouldn't consider that.
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Old 11-16-2010, 05:57 PM
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I was looking for a 1/2 sending unit and could not find one. Is the one your talking about a replacement for the ones in the tanks of these cars? Also do you know anyone or have you ever modified the sending unit with a 1/2" line. I would think that would be the less money spent route?
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Old 11-16-2010, 07:54 PM
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I also ran a 1/2 fuel line. mine was hand bent aluminun line. When it was time to connect the line to the tank I was too broke to buy a fancy sending unit. So I bought a few fittings, adaptors and a couple feet of braided fuel line. I drilled a hole in the bottom of my tank and plumed everything up to the aluminum line.

http://www.hotrodders.com/gallery/sh...cat/500/page/1

I couldn't figure out how to post a picutre but that is a link to the picture in my gallery showing how I did it.
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Old 11-16-2010, 08:05 PM
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When you say you drilled your tank exactly what did you do? Just drill and screw a fitty in... and how did it hold up.
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Old 11-16-2010, 08:38 PM
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I went to my local speed shop and told the guy what I was doing. He was really helpful and showed me everything I needed to get the job done. He gave me a fitting to go inside my tank. I used to step drill bit to get the hole the correct size. The fitting went inside my tank and was sealed by a Nylon washer that went on both the inside and outside of the tank. A nut was used to keep the fitting held snugly inside the tank.

Here is a website. Ill list everything I used to make mine work.

http://www.anplumbing.com/shop/index...&dept=Aluminum

He gave me a Union-Male A.N. TO A.N. Adapter. Part number 981508
The nut that goes inside the tank to hold the AN fitting in place. Part number 992408
A nylon washer went inside and outside the tank.
A Swivel-Seal 90 deg. Tube Hose End threaded onto the A.N. adapter.
Part number: 809108

The swivel seal is used to attach my fuel line. Than up top their is another fitting on the end of braided line that attaches to the aluminum line. It acts like a crush sleeve.

My fuel line feeds a hungry 496 big block Chevy in a Pontiac Station wagon. I don't have any leaks or any problems. The thing to keep in mind is where you drill the hole because you don't want the feed to become dry when the fuel level drops.

Hope this helps a little. Hope it doesn't seem too confusing.
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Old 11-16-2010, 10:09 PM
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Quote:
Originally Posted by obengston
I was looking for a 1/2 sending unit and could not find one. Is the one your talking about a replacement for the ones in the tanks of these cars? Also do you know anyone or have you ever modified the sending unit with a 1/2" line. I would think that would be the less money spent route?
The RobbMC Performance unit is a drop-in replacement for the stock sending unit/pick-up that fits into the top of the tank, held in with the factory lock ring and sealing O-ring. it is assembled and ready to go out of the box. Google "Robbmc sending unit" and it will come right up, they make quite a few very nice fuel system parts, including a big billet mechanical pump.

I have done the sending unit mod before, you have to carefully cut and drill the stock line away in pieces from the sending unit main plate taking care to not ruin the plate, and fit in a new 1/2" replacement copy line and solder/braze/TIG weld it in to make a seal. A bit of work, nothing really hard if you have welding and fabrication experience, just takes time. You'll have to bend up your own replacement line section to solder in, from a chunk of 1/2" tube. You will need a GOOD tube bender(Imperial Eastman or Rigid), like used for hydraulic lines or aircraft work, to be able to bend the 1/2" tight enough.
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Old 11-17-2010, 05:04 AM
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Thanks for Both replies above. Great info. Now I just really need to decide of the 3 which is best for me.
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Old 11-17-2010, 06:47 AM
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ask a few of your friends....

if they know someone that works in the maintance dept of a manuf plant... they will have reducer unions in ss, brass etc. make sure they are double ferl fittings. swagloc, gyroloc etc are some of the better fittings. if u want to use this type of fitting just turn 3/4 turn after finger tight or u can cut threw the tubing..
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