Fuel vaporizing issue

[nqkjw]

If you do build a full flow(return) system make sure the return is delivered submerged.If you just dump it into the top of the tank the percolation will kill your octanes.
And preferably away from the delivery outlet.You don't want to just recycle the same fuel as the return fuel is hot and you'll be almost back to square one.

[ff6849]

 I am going to the full return system, ordered everything last night, is there a simple way to convert my 1/4 return line in my sending unit to a 3/8. I was thinking of using some type of bulk head connector. What have you all done? 

[72cudamaan]

If you do build a full flow(return) system make sure the return is delivered submerged.If you just dump it into the top of the tank the percolation will kill your octanes.
And preferably away from the delivery outlet.You don't want to just recycle the same fuel as the return fuel is hot and you'll be almost back to square one.

Interesting concept. Could you elaborate please?

[brads70]

I just ran my return line into the filler neck. I drilled a hole then welded a AN-8 fitting to it.

[72ls5fla]

Are you running higher than E10 fuel?

The more ethanol in the fuel - the more rapidly it will boil.

[cudabob496]

Hmmm, sure seems a decent high output mechanical pump will do the job, given
all the other usual stuff is taken care of.  I would try to solve this problem by doing other more
simple stuff, before I'd go to the trouble of an electrical system.  After all, even if you have
the electrical system, you may not have solved what was causing the problem in the first place.
But, just my two cents!

Could be something simple, like vent gas cap, eliminate filter on suction side of pump, or
proper heat shielding of fuel line.

[cudabob496]

If you do build a full flow(return) system make sure the return is delivered submerged.If you just dump it into the top of the tank the percolation will kill your octanes.
And preferably away from the delivery outlet.You don't want to just recycle the same fuel as the return fuel is hot and you'll be almost back to square one.

What are the drivetrain details on your black barracuda?

[msbaugh]

You do not need to use 3/8" line for your return, 1/4" will be fine the 3/8 is over-kill if you ask me, I would use 3/8" for your main feed however.  Electric fuel pump is a great idea, but main thing is to keep fuel lines away from headers if you have them.  I don't recommend using header wrap, it's not any good on street cars. 
Put a carb spacer if you have room.  A plastic/wood one seems to do the trick very well, If you don't care about originality. It isn't always boiling in the fuel lines, a prime place is right there in the carb.  A 160 thermostat and DEFINITELY block the heat cross over passage on your heads.  That could be the number one cause if you haven't done that already.
Here's a link to a great company that makes thermal protective stuff for plumbing and wiring.  Expensive, but works better than any foam or aluminum foil, plus it won't look like crap.

http://www.summitracing.com/parts/the-18075/overview/

I laugh at you guys from Colorado mentioning hot weather.  I live in south Texas, I've dealt with the heat soak ever since i bought my car...  100+ degree days are every day during summer time, I think I'm the only one not excited for winter to be over!!

[cudabob496]

You do not need to use 3/8" line for your return, 1/4" will be fine the 3/8 is over-kill if you ask me, I would use 3/8" for your main feed however.  Electric fuel pump is a great idea, but main thing is to keep fuel lines away from headers if you have them.  I don't recommend using header wrap, it's not any good on street cars. 
Put a carb spacer if you have room.  A plastic/wood one seems to do the trick very well, If you don't care about originality. It isn't always boiling in the fuel lines, a prime place is right there in the carb.  A 160 thermostat and DEFINITELY block the heat cross over passage on your heads.  That could be the number one cause if you haven't done that already.
Here's a link to a great company that makes thermal protective stuff for plumbing and wiring.  Expensive, but works better than any foam or aluminum foil, plus it won't look like crap.

http://www.summitracing.com/parts/the-18075/overview/

I laugh at you guys from Colorado mentioning hot weather.  I live in south Texas, I've dealt with the heat soak ever since i bought my car...  100+ degree days are every day during summer time, I think I'm the only one not excited for winter to be over!!

Ya, my sister lives near Dallas. You guys cook!!!

[ff6849]

So a 3/8 supply line will work with the existing 1/4 return, I wanted to update my fuel line anyway, so I am just going to use the old 5/16 as the new return and then connect that to the 1/4 return fitting on the sending unit, from the feed back I gather that should just work fine.

I did install a keep it clean wiring harness (a painless knockoff) so I have a dedicated circuit for the fuel pump. I ran the wire to trunk and tucked up just in case I would need it later down the road (I guess I am down that road). So switching over to electric fuel system shouldn't be all that difficult.

I live in one of the hottest places on earth, we see temp's in excess of 110', it was almost 90' this weekend so I am going to be fighting heat issues on regular basis.  So in the long run this upgrade should work well for my circumstances. I do have a venting cap so I am not creating a vacuum or pressurizing the tank. 

I was thinking of up grading my mech pump, but that is about the same cost of the electric pump, and having a return in the southwest desert just makes sense.  Plus I really would like to install a FAST EZ EFI later so I am setting my fuel lines now if I want to make that switch later down the road too.

This is my first project and I couldn't of done it without all of your advise, so thanks again for solving another issue.  I did my first big car show this week and got a ton ohh's and ahh's it was annoying though explaining that its not a Camaro or a GTO  

[nqkjw]

What are the drivetrain details on your black barracuda?

Reverse pattern manual 727 with 4000 stall.
Spooled 8.75 with 3.73 gearing and billet 30spline Currie axles on a 28" tall tyre.
Street rubber is 275/60/15 on 8.5" rim
Race rubber is 28x10.5x15 on 10"rim

[nqkjw]

A full flow system should have the return lager diameter than the deliver.
Same size as a minimum.
I made that mistake on my 69 barracuda.
Built 1/2" delivery with 3/8" return and had to set the reg wide open to get the dlivery pressure low enough.
The smaller diameter return ends up being the the restriction that governs your pressure.
Fortuneately in my case I've done a small mod to my floats/needle and seats to allow me to run at 8.5-9 psi.
And that's just a Holley blue.
It's easier to keep higher pressures stable.

You'll need a bypass reg or if you like a can show you how to plumb up a normal holley reg to work as a bypass reg.

[72cudamaan]

Still trying to understand "percolation will kill your octanes". What does that mean? I'm not disagreeing, I had just
never heard that statement before.

[ff6849]

I did order the a Holley by-pass regulator, how much pressure is in the return line, since it going to an open orifice and dumping into an unrestricted tank there should be any residual or back pressure on the regulator. 

[73EStroker]

You do not need to use 3/8" line for your return, 1/4" will be fine the 3/8 is over-kill if you ask me, I would use 3/8" for your main

If you run a bypass regulator (which is the correct way to do a return system IMHO) then you must use a return the same size or larger than the supply line. What happens if u don't is the recirc pressure bleeds off into the carb with pressures as high as 15psi which forces gas past the carb needles. Then you have cylinders full of liquid gas and the engine does not turn over. Ask me how I know all of this!!!!!!!