Gas tank becoming pressurized???

[C5GTO]

I've ordered up the fittings and tip over valve needed to redo the fuel return line and tank venting. I started the mods to fuel fill pipe to install a 3/8" stainless tube for fuel return. It looks like the return tube can go down to about middle of the tank, so until the tank goes below half full, the return full won't have a chance for further aeration. The tube exit will be onto a sloped/curved surface so even below a half tank it shouldn't have much risk of aeration.

I'll post pictures of the mods so others with CRL Cobras and EFI can potentially benefit.

[C5GTO]

The fuel system mods are complete.

For the fuel return line, a 3/8" SS tube was silver soldered into the "S" bend fill pipe and a -6 fitting silver soldered on the end so a -6 SS braid hose could connect up with the return line.



For the fuel tank venting, a hole was drilled into the LeMans cap base and tapped for 1/4" NPT threads. A series of fittings and a tip-over valve were installed and these connect to the fuel tank vent pipe with a 1/2" hose.





Once all the bits were re-installed, the small black hole under the flip cap and the three extra holes in the top are the only external visible parts of the modifications. I did run a ground wire as Morris suggested from the LeMans fuel cap to the battery ground to help avoid static electrical discharges where fuel vapors may be present.

So for about $150 in fittings and hoses, the fuel tank should now be properly vented and fuel returned to the tank. I'm going to monitor for the smell of excessive fuel vapors and if so, will look further into the fuel pressure regulator setup. Thanks for all the input and information from those who've commented on this thread. The end results came out very clean thanks to Morris's suggestions.

Now for some spirited test drives to make sure the fuel tank pressurization issue has been fully resolved

[Morris]

Joel

I'm not sure the Silver Solder is the way to go....do you have some one that can Tig weld the pieces together.....just not sure I would trust the silver solder??

other then that ...it looks good and should work fine.

[C5GTO]

Originally Posted by Morris

Joel

I'm not sure the Silver Solder is the way to go....do you have some one that can Tig weld the pieces together.....just not sure I would trust the silver solder??

other then that ...it looks good and should work fine.

I actually chose to use silver solder over TIG welding for this application. I used an industrial silver solder alloy that is most commonly used to attach carbide points to saw blades and machine tools. It should have plenty of strength given that there's really no stress on those parts. The hose that attaches to the tube is all of 4 inches long in a straight run and clamped to the chassis frame just beyond the hose end.

I have a TIG welder and have welded lots of SS things. Welding thin wall SS tubing (.028 wall in this case) can be fairly tricky in that you can easily plug or restrict the tube during welding. You don't run that risk with silver solder as the base metals never reach melting temperatures.

I'll keep an eye on it just in case. After getting it back together, I did take the car out for a drive including a tank fill-up. No tank pressure build up or gas leakage so far. Thanks for your help!

[CHANMADD]

I run a deadhead at the regulator up front, the top cap is sealed and then I have a rollover, tip valve/breather in the rear fender well.

[CHANMADD]

Originally Posted by sunman

The fuel tank does not vent to atmosphere. You have a check valve in the gas cap and a vacuum line to the tank.
The EGR pump injects fresh air into exhaust to trick emissions testing or help complete fuel burn whatever you want to believe, it’s a separate part of system.

These are not smogged legal cars.

[sunman]

I never said they were. The sealed tank is going in the fan vented trunk with flush cap Holley EFI 12 bolt hat. You could use a 5 hole EFI pump/vent/return unit and a LeMans sealed cap with tank in original location.
Ed’s “add a fuel hat“ sounds good and I can put cell foam and a pickup tube anti-starvation dam thru the hole.
Cut off and seal filler tube and vent. No EGR pump.
The tanks are made by Tankcraft in Wisconsin and they are heavy duty might as well use it.
Velcro to hold it down

[eschaider]

Joel,

Been away for a bit and just read your silver solder approach. Good idea! Another good techinique is to use a sililcon bronze filler rod. It melts at a lower temperature than steel, just like the silver solder, but might provide an even stronger attachment. Particularily handy when joning different thicknesses and one is down in the 0.030 / 0.060" range like tubing.

Ed