I have a puzzle for you
 

I have purchased a couple of these tanks for my 1985 RX-7. One will be used to supply 2 cycle oil to the carb via an oil pump adapter. The other will be used as a radiator overflow. The instructions say that if it is used as a overflow tank with recirculation, connect the radiator overflow tube to the bottom of the tank. This way the radiator can suck any fluid back in to the radiator when needed. The top cap is vented.

I want to convert this to a tank similar to the current factory tank. The factory tank has a "straw" within the cap that sucks the fluid back when needed.

My puzzle is this: How do I get an aluminum tube to to adapt to the 1/4 NPT thread in the top? I want to use 6AN fittings and nylon braided line. I thought about using a 8" 1/4 NPT nipple. The issue is that I cant find any that are threaded all the way. My other thought was to use aluminum fuel line and flare it some how and then find some sort of adapter.

http://www.jegs.com/images/photos/500/555/555-51145.jpg

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Put the hose on the bottom of the tank, not the top sucking through a straw. Problem solved.

I think your right. keep it simple and less expensive.

I think I found another solution. I ran across this marine fuel pickup. This will install in the 1/4 NPT opening in the top. I would then need to drill a small hold in the top of the tank for a vent.

New Moeller Fuel Pickup Poplock 360deg 12" Moe 03310012 | eBay

http://www.starmarinedepot.com/smd/i...r/ZZ5431_L.jpg

Couldn't wait so I just went ahead and purchased the fuel pickup. The reason I went this route is because it will make the pluming look better visually. I'll just run a nylon braided line from the radiator barb fitting to a -4an or -6an fitting that will connect to this fuel line pickup. Not sure yet if I'll need -4an or -6an until I get some samples of each line.

Well, the fuel line pickup didn't work. The tube was two big. What I came up with was to solder a 1/8 copper pipe to the inside of a 1/4 NPT nipple. Works great. The trick is to ensure that that solder make a complete seal. If there is any air leaking the tube will not siphon the water up. It will act like a straw with a hole in it.

http://i1133.photobucket.com/albums/...ps312fc243.jpg

The tank on the left will be used as a 2 cycle oil supply for the OMP adapter. The tank on the right will be the radiator overflow tank.

http://i1133.photobucket.com/albums/...psa5933c7d.jpg

I got the tanks and fittings from Jegs. The tanks are advertised to hold 28oz. The AN adapters are 6AN and the NPT fittings are 1/4.
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I approve of this post.

You could have also just soldered a tube with the right diameter to the fitting. I've done it before and it is bomb proof.

I was able to eliminate two fittings by using this 1/4NPT to 6AN fitting. The 1/4 NPT inner diameter was smaller on this one so less soldering, tighter fit, and easier to center. I'll do the same type of connector and tube for the bottom whole also. This way the tank fills from the bottom-up and drains from the top via the internal tubes.

http://i1133.photobucket.com/albums/...psc77cef0f.jpg

Made some progress on the oil tank. I've installed a mid 1990's oil tank float from a Polaris snow mobile. I'll install the light somewhere in the interior. Not sure if I'll use the light that came with it or another one.

http://i1133.photobucket.com/albums/...ps8de8ff4e.jpg

http://i1133.photobucket.com/albums/...ps0841cce6.jpg