Gas Smell

[nathanmargolis]

Have Backdraft #357 built in 2006 by Vintage and had the car for almost a year now. Previously kept a '69 Stingray in the garage before Hurricane Harvey in Houston for 20 years.

I know carbureted cars will have a gas smell as the Stingray did. The Cobra has one but is stronger than the Corvette by far. This is the only vehicle kept in the garage.

Have checked thoroughly the fuel lines, gas tank, carburetor on a lift and areas underneath the Cobra while parked. Absolutely no leaks. Have check the Holley venturi right after shut down and no drainage. Carb has no signs of leakage. Car runs fine and idles nicely at 900-1000 RPM. Even checked float levels and that correct. Have not made any carb adjustments as car runs fine and want to leave well enough alone on that.

QUESTION: Cobra has real stainless braided fuel lines in engine bay. A reputable engine and high performance mechanic who installed a Vortec blower on a S95 Mustang once owned told me that these type of fuel lines are known to permeate (release) fuel odor even though there is absolutely no leaks in the hose. HAS ANYONE ELSE HEARD SOMETHING LIKE THIS OR HAVE A STRONGER THAN ONE WOULD THINK FUEL SMELL IN A TWO CAR GARAGE? When the car is running in an open area like sitting at a red light, you do not smell a fuel smell.

Appreciate comments.

Best,
Nathan in Houston, Texas

[Gaz64]

I've never liked braided line, especially for fuel.

The hose does permeate, cannot tell from the outside until it is too late, and the braid is a conductor, so the chances of an electrical/fuel fire are much higher.

Braided brake hoses are fine, since they are a teflon hose.

Gary

[DanEC]

Rather than look down the carburetor throat right after a hot shut down - go back about 10 minutes later and look down the carb venture, particularly the primary ones. It may be the heat soak after shut off that starts fuel flowing through the accelerator pump or idle circuits. At least that is how mine behaves (and stinks). Gaz64 has recommended a modification on the accelerator pump umbrella seal but I haven't gotten around to it yet.

[Cashburn]

There was a recall on many types of braided line sold in that era. I would believe that to be your source. I’ll look at photos tomorrow and see if you have one of the brands.

[Cashburn]

I don’t see a 357 in my records... tell me more about the car?

[HTM101]

Originally Posted by nathanmargolis

Have Backdraft #357 built in 2006 by Vintage and had the car for almost a year now. Previously kept a '69 Stingray in the garage before Hurricane Harvey in Houston for 20 years.

I know carbureted cars will have a gas smell as the Stingray did. The Cobra has one but is stronger than the Corvette by far. This is the only vehicle kept in the garage.

Have checked thoroughly the fuel lines, gas tank, carburetor on a lift and areas underneath the Cobra while parked. Absolutely no leaks. Have check the Holley venturi right after shut down and no drainage. Carb has no signs of leakage. Car runs fine and idles nicely at 900-1000 RPM. Even checked float levels and that correct. Have not made any carb adjustments as car runs fine and want to leave well enough alone on that.

QUESTION: Cobra has real stainless braided fuel lines in engine bay. A reputable engine and high performance mechanic who installed a Vortec blower on a S95 Mustang once owned told me that these type of fuel lines are known to permeate (release) fuel odor even though there is absolutely no leaks in the hose. HAS ANYONE ELSE HEARD SOMETHING LIKE THIS OR HAVE A STRONGER THAN ONE WOULD THINK FUEL SMELL IN A TWO CAR GARAGE? When the car is running in an open area like sitting at a red light, you do not smell a fuel smell.

Appreciate comments.

Best,
Nathan in Houston, Texas

Yes, I had the identical issue for years. I had installed stainless braided hoses in my trunk. They were plumbed to 2 Stewart Warner fuel pumps. Whenever I raised the trunk I always smelled gas fumes but there was never a leak.

Some years later I decided to replace the braided lines with black rubber lines because they were more period-correct looking. Immediately after replacing the braided lines, the gas fume smell disappeared. That was 8-10 years ago and I still don't have any gas odor in the trunk.

[sllib]

I replaced my ss braided fuel lines with XRP brand lines and my problem went away. XRP is pricey but a lot of racers swear by it.
Bill

[nathanmargolis]

Excuse me Cashburn, it is number 329 in the book. Originally sold to the Englishman.

[Cashburn]

Originally Posted by nathanmargolis

Excuse me Cashburn, it is number 329 in the book. Originally sold to the Englishman.

Well #329 did not have stainless braided lines when we built it. So did someone change them?

[nathanmargolis]

Hi Cashburn,

I looked at probably the same pictures. Attached (or maybe not) is a recent picture of the car at a car show in College Station, Texas. Actually the fuel line is a black braided line until it gets to the Holley and then that is stainless braided. Was there an issue with the black braided fuel line?

James Yale made mention that some of the smell is because of the short side exhaust. I realize there will be a odor but this is really strong.

Nevertheless, the car has been amazing and have put 1,400 miles on the car in the last 6-8 months once getting past the wheel problem where James had to cut one of the wheels off as it seized to the pin drive.

Thank you for the response.

Nathan Margolis
Houston, Texas

[eedeutsch]

I had a gas smell with my Backdraft. It turns out the carb (Holley)needed a rebuild.

[MOTORHEAD]

I would expect the carb would leak, parked upside down like that !!

[nathanmargolis]

Dear eedeutsch,

Funny thing you should say the carb needed rebuilding as the Holley Advanger is off the car and being rebuilt by DaVanci Performance Carb here in Houston. Did not pull it off because of the smell but developed serious hesitation and flutter when giving gas from a roll or shifting gears. Checked many things out like accelerator pump, squirters in carb, plugs, MSD ignition, and fuel filter. All appeared fined. Figured that the ethanol in gas must have gotten to the carb and internal gaskets.

Carb has been off the car for a week now and garage does not have the heavy smell of gasoline now. When I did pull the carb off, did not actuate the accelerator pump or throttle plates and noted the intake runner planes were wet and the car was not started in over a week. Appears that there must have been an internal leak of fuel that could not be seen and other problems on this ten year old Holley.

Should have carb back on in a few days and if it ever quits raining, looking forward to some Cobra miles before too hot here in Texas to be driving.

Still an interesting comment as I have never heard that a heavy gasoline smell in a garage could be a faulty carb. But I bet you are correct. Will let you know.

Thanks,
Nathan

[eschaider]

Nathan,

The bladders in the majority of the stainless braided lines available today were never meant for gasoline. Their hose's rubbery bladders allow gas to seep slowly through the membrane producing the majority of the gas smell you probably notice. Boiling the gas in the carburetor on a hot engine after shut off will easily provide the rest of the gas vapor you are smelling.

The carb problem can be mitigated (but not completely eliminated) not only by a rebuild with newer, better components but also by using some one of the many aftermarket heat insulators between the carb and the manifold. Here is a link to an Edelbrock version of the product, click here => Carb Heat Insulator. Even with a good insulator you will still vaporize some of the fuel in the carb after shut down.

The hose is a more complete fix. If you replace your braided stainless hose with its polymer bladder with a teflon lined hose, like is used on braided stainless brake lines but larger, the seepage through the rubbery bladder will completely disappear.

If you prefer to avoid the braided stainless appearance the hose manufacturers also provide non stainless covers for the teflon lined hose.


Ed


p.s. I like your colors — same as mine ...

[undy]

Originally Posted by MOTORHEAD

I would expect the carb would leak, parked upside down like that !!

You beat me to it...

[nathanmargolis]

Dear eedeutsche,

Had the carburetor rebuilt by Davanci Carbs, who is located in Houston for reasons mentioned above (hesitation, sputter, and flutter). All that was solved and along with the garage does not have a heavy gas smell like it once existed. Clearly, you can smell there is a carbureted vehicle enclosed but not even close to what it was prior to carb rebuild. So you were right about carb needing rebuilt because of the heavy gasoline smell.

Thanks,
Nathan