Need Verification on Fuel Tank Threads

[Dan Carter]

Gents I discovered a leak at the fitting that feeds the fuel pump from the tank (the bottom one on the tank). What type of thread did RCR use on the tank, I don't see it in my notes anywhere? I'm hoping I used the right type of adapter thread into the tank.

Thanks

 

[Cam]

Man that’s a supreme bummer Dan I had an issue with that same location, blamed it on the fitting. I pulled my old fitting out and munged up the threads. I can’t recall now what I used to re-tap it. I’m guessing it must have been a 3/4” NPT or thereabouts. I do recall sending the new tap a lot deeper than the original hole, but I was trying to make up for some material I had lost when I managed to get the original fitting out. I packed the tap with a bunch of grease so shavings wouldn’t fall into the tank. Seemed to work okay, I didn’t go through another round of tank cleaning because I was being lazy.

See my adventures at this post:

https://socalslc.com/2017/12/02/20-ignition-a-tale-of-highs-and-woes/

 

[Roger Reid]

Sounds like Joel and I both need to check this fitting and thread depth as we are both early in our builds.

 

[Dan Carter]

I looked for any signs of a cracks around the bung weld and it seems to be clear. Everything I have read says to make sure and use a sealant on NPT threads, but to also make sure its designed to be gas resistant in this case. While the first sealant I used stated it was gas resistant, it doesn't appear that way. I'm letting the new sealant dry before adding gas back in. Fingers crossed.

 

[Ken Roberts]

Sometimes the bung distorts from the heat of welding. Running a NPT tap in a little bit after it snugs up will help with the fit up of the fitting.

 

[Joel K]

Good luck Dan, hopefully you get it back on the road soon. Looking forward to more driving reviews.

 

[Rich Kruger]

Dan what was the first sealant you used? I used permatex #3 aviation sealant. It did leave a question in my mind as it said that alcohol may affect it. I haven't put fuel in the tank yet so I'm curious how successful you are. What did you try the second time around?

 

[Scott]

Dan,

The tank has two 3/8" NPT bungs at the top and one 1/2" NPT bung at the bottom. I know that they are used in many applications, but I !*@&^ hate NPT for fuel. I pressurized the tank to test it and no matter how much I tightened the AN fittings, I couldn't stop one slow leak. To solve that I removed the fittings and applied a little Permatex Aviation Form-A-Gasket:

Slow-drying, non-hardening brush-top sealant approved for use in aviation as well as automotive applications. Temperature range -65°F to 400°F (-54°C to 204°C); resists gasoline, oil and grease. Application: Close-fitting machined surfaces, sealing hoses, solid gasket.

After using the Permatex I re-pressurized the tank and I hadn't lost any pressure by the following morning. Hopefully mine don't develop a leak. I wish that Superlite used ORB rather than NPT bungs.

 

[Dan Carter]

Gents

The first sealer I used was Permatex High Performance Thread Sealant. It worked for about nine months. No leaks. I pulled the 1/2 NPT fitting, cleaned it and the tank threads. The second sealant is again Permatext High Temperature Thread Sealant. I won’t know until tomorrow if it will work. It’s curing at the moment.

I saw the aviation stuff and all three say fuel, but non say ethnology gas. I think I will call Permatex before I add gas again.

 

[Dan Carter]

OK gents, passing this along for what its worth.

Found out some things you may want to know. In talking to Permatex, they advised me that they had to rebuild their formulas for thread sealer and this new stuff is not as effective on todays gas as it used to be. As I understood it, the main ingredient that proved so effective on the ethanol in gas today, was South Georgia Pine Sap....the irony here is, its where I live. It took several months for gas to eat thru my Permatex thread sealer and start to leak.

Anyway, the recommended product from the technician I talked to, to use on tanks (I have some on order) is Gasoila E-seal Thread Sealant (Yellow Can). It is designed for E-10 and E-85 blended gasoline.

 

[Howard Jones]

Here's what I think. It's not the mainstream opinion. I don't like ANY penetration of the fuel tank that will allow a full tank to leak fuel due to gravity if a hose or any other component down stream attached to it fails in any way. Not every leak can be prevented but this one can.

When I first Iooked at my fuel tank I saw a huge fuel leak if a hose failed due to the bungs you guys are talking about being at the bottom of the tank. I covered them all up and welded a the plate in place.

All of my connections enter the fuel tank from the top through either the fill plate or a second fuel delivery plate. The pump must pump up hill to get the fuel out of the tank.

Should the car get upside down. All the openings have roll over protection.

 

[Neil]

If you are using a true "fuel cell" (a flexible bladder within a metal container), all of the connections are through the cover plate at the top. A fuel tank is not a fuel cell. No criticism of anyone intended- I'm just trying to clarify what is a fuel cell and what is not.

I recommend using one in a high performance homebuilt, even for street use. A fuel cell may be expensive but so are a few days in a burn unit.

 

[Dan Carter]

Good discussion. Never thought about the location of the exit port.

Installed the Gasiola about 3 weeks ago now and the leak has stopped. it took the Permatex a long time to give in to the fuel, so time will tell. The Gasiola is an odd thick paste that is applied by brush. For the new builders, do your homework on the fuel tank and make sure you have access to everything after the car is assembled, you never know where you may need maintenance.

 

[Joel K]

Howard, now you have me thinking. Since I’m going with a stock fuel pump mounted face up in the tank, I was thinking of keeping the lower bung in place and put a shut-off valve on it just in case I needed to drain the tank. But maybe that is just a problem waiting to happen and I should just weld it up. I guess if I want to drain the tank I could just siphon through the filler neck.

 

[George]

Since you guys are on this subject, I need some help on the best way I can vent both aluminum fuel tanks??? Thanks

 

[Ken Roberts]

There are a few cars that have been out there on the roads with lots of miles on them. Cam in Texas and Stu in Australia. This is the first I have heard of a fuel leak at that fitting. Everyone with a swirl pot uses this tank exit. Thanks for the "gasiola" advice.

 

[Dan Carter]

George

Not sure about your complete setup, but for simple fume venting take a look at a product called Much II. Summit has it. Pretty simple and affective.

 

[Ken Roberts]

For anybody currently using the Much II vent...........apparently there was a recall last year on the them.

https://www.iimuch.com/search?x=0&y=0&q=recall

 

[Howard Jones]

Neil, No I do not have a fuel cell. Only a big aluminum box (like all production cars). Why....in a track only car? Fuel cells are very expensive. $1000's AND the fuel cell manufactures will tell you if you ask that they do not warranty them if you run pump gas, only race gas or 100% methanol AND you still have a service life of 4-5 years. What it comes down to is nearly a $1000 bucks a year for a bladder style race fuel cell for the first service period on a custom cell. So why no warranty? They have no idea what you will put in the fuel bladder or what is in the pump gas you use.

When I asked around to other track day type guys nobody used one. Mainly due to cost. You gotta pick your risk...……….I guess.

I am not saying that all of you guys SHOULD weld up your bungs. I only offer a different point of view. It's a fail safe thing for me.

My tank has three transverse bulkheads in it that divides it into 3 sections. All 3 sections drain into the center one via holes at the bottom rear. It also has a sump in the center section that the pump draws from and it holds about a 1/4 gal. So far the tank seams to draw all the fuel out before I see any low fuel issue, so I think I have addressed any potential slosh problem.

I would have added another top plate so I could fill it with foam but the foam seams to have the same issues with pump gas and deteriorates quickly to eventually depending on who you talk to.
One of these days I am going to track down the metal expanded metal explosive safe stuff in my GTD's gas tanks and add it to my SLC. That's one thing I regret not doing when I remade my tank.

Joel, I can pump mine out down to the last cup or so with the regular pump so I don't see any need for a drain on my car.

 

[Neil]

Howard, my Fuel Safe 10 gallon flexible bladder cell cost me around $900, not thousands. Accessories and an aluminum container run the cost up, though. I have an aversion to being burned but, like they say, "You pay your money and you take your choice."