Gas temperature in tank

[AlanCasida]

This may been discussed but I couldn't find it. After driving my '65 Mustang(FE powered) about 60 miles on a 90+ degree day I checked the temp of my aluminum fuel cell and it was around 125 deg. Is this going to be a issue driving down the highway? I have a return style fuel regulator with an electric fuel pump feeding a carburetor.  When I built this car my main interest was to haul it to the track and just makes some passes and maybe short drives. I didn't figure on driving 1200 miles in a week. So the fuel lines run fairly close to the exhaust systems on places. I have wrapped the exhaust and fuel lines in those areas but in that small of a car there just isn't enough room for everything to be separated.

[gdaddy01]

did you use a heat gun to check temp ?

[Drew Pojedinec]

He is getting at the point that IR guns don’t work so well on bare metal.
Paint a spot to check.

I believe your fuel tank is 125.
Not a huge fan of return lines for this reason.
I get the idea that fuel gets purged etc but why send it to the engine bay to get hot in the first place?

[AlanCasida]

I am using an IR gun but it is really hot to the touch too. That's after 60 miles and a little over an hour. I am concerned what it would be after 6 hours and over 200 miles.

[shady]

Maybe a cool can.

[My427stang]

Returning fuel can get the tank hotter, but I doubt it will continue to increase if it is just heating from the engine.  It may be worth a longer drive, but I am not sure I would worry too much. 

In the end though, it really depends why, and if the source is the exhaust, the temp in the tank is less concerning than localized heating of the line and vapor lock or boiling the fuel.

It may be a pain in the butt, but I'd think  there has to be a way to get it away from the exhaust or shield it even more.  My guide would be, if you can't hold your hand on that fuel line near the exhaust after it's warmed up, you should find something better

[AlanCasida]

Returning fuel can get the tank hotter, but I doubt it will continue to increase if it is just heating from the engine.  It may be worth a longer drive, but I am not sure I would worry too much. 

In the end though, it really depends why, and if the source is the exhaust, the temp in the tank is less concerning than localized heating of the line and vapor lock or boiling the fuel.

It may be a pain in the butt, but I'd think  there has to be a way to get it away from the exhaust or shield it even more.  My guide would be, if you can't hold your hand on that fuel line near the exhaust after it's warmed up, you should find something better

If I got rid of my tail pipes and turned the exhaust down at the rear axle that would solve about 90% of the heat issue. But since I ran the exhaust out through the rear valance that would mean buying and painting a new valance and having to deal with the extra noise dumping the exhaust out under the car brings.

[machoneman]

Some European cars (maybe American too) do have simple tin or sheet steel shields underneath where the exhaust pipes are routed close to the gas tank. May be worth a try.

That said, my '70 Mustang's exhaust pipes run quite close to both sides of the OEM gas tank. Never worried since millions of miles and literally millions of Mustangs have had the very same issue for decades now and I've never heard of exhaust heat causing an issue.

Underhood heat? That's another story on vapor lock on really hot days.

[AlanCasida]

Some European cars (maybe American too) do have simple tin or sheet steel shields underneath where the exhaust pipes are routed close to the gas tank. May be worth a try.

That said, my '70 Mustang's exhaust pipes run quite closeto both sides of the OEM gas tank. Never worried since millions of miles and literally millions of Mustangs have had the very same issue for decades now and I've never heard of exhaust heat causing an issue.

Underhood heat? That's another story on vapor lock on really hot days.

It's very possible I am concerning myself about a problem that doesn't exist.

[chris401]

If your return line is catching rising heat from the exhaust maybe you could slide a piece of aluminum tubing over it. Can't think of any modern car I've noticed the tank being hot to the touch. Seems they are all plastic. Along the lines of Shady's point maybe there is a cooler spot you could route the return?

[BattlestarGalactic]

Have you checked the temperature at the regulator?  Is it 125* there coming from the back?  Or only returning after being near the engine? 

With all the heat from engine/trans/rearend all moving towards the rear of the car I would think the aluminum tank would try to absorb it.  How about a plastic shield to keep the heat out?  Insulate any lines near the exhaust and then recheck your temperature at the regulator to see if it is getting cool fuel or hot.

Just some thoughts.

[Stangman]

Allen im to dumb to send pictures but my return line and inlet lines runs up drivers side on outside of the frame rails that go under seat and through torque box and inside fenderwell and go through engine compartment in front of shock tower to the regulator which is mounted in between shocktower and radiator. The return is in the engine compartment for only 1 foot. The only fuel line that can get hot is the line that goes to the dual quads and I have that one shielded. So pretty much 95 percent of my lines are not in engine compartment for the main reason to keep them as cool as possible. I will send pics threw phone if you would like.

[AlanCasida]

I just got back from another 50 mile drive( I would have went further but my GV quit working again). It's about 90 here today with a heat index of 98. The temp on the tank was around 115 according to my ir gun.  I took the lid of the tank and checked directly in the tank and read about the same. So I stuck my hand in it and it wasn't overly hot to the touch. I have the lines ran on the outside of the frame and they run up the outside of the fenderwell up front so only a couple of feet of fuel line is in the engine compartment. I already have my lines insulated where they run close to the exhaust and have wrapped the exhaust in the same places too. Where it is real close in one spot I also  made a shield for it too. While I was getting gas I crawled under the car and felt the lines where they run close to the exhaust and they felt ok. Under the hood the regulator felt ok too. I have it mounted on the water pump and it is right in front of one of the electric cooling fans. The electric fuel pump felt ok too(I have an insulated shield around it and a muffin fan blowing air on it from inside the trunk).   I have probably been overreacting...I don't know. I guess my question has been will it hurt anything if it gets pretty hot? I know cooler fuel at the track is supposed to work better but I will have plenty of time to let it cool off before I make a pass. 

[Russ67Scode]

I have a similar problem my cell  which is inside my trunk isolated from underneath the car and after a 70 mile drive was 123° 
My exhaust stops at the front tires as it’s a turbo car the difference is my car is fuel injected going to run a cooler in the trunk for the return line

[cammerfe]

Years ago, when Brother Lon and I were racing his 427 TP '67 Mustang, we had a pair of S-W (clop-clop) electric fuel pumps mounted in front of the tank under the car to feed the dual quads. We mounted a 'cool can' in the engine compartment against the inside of the rad support. On Sunday morning, early, the milkman would deliver a block of dry ice for us to take out to Milan.

The cool can was filled with isopropyl alcohol. Before each run we'd drop enough dry ice in the alcohol to turn it syrup-y. After every run, by the time the car got back to the pit, the alcohol would be almost as warm as bathwater. A lot of heat was coming from somewhere. But our goal was to be able to make repeatable runs. And we could run three or more runs all within a couple of thousandths. We hit our goal.

KS