Feul Percolating in tank!! - Team Camaro Tech
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post #1 of 14 (permalink) Old Sep 16th, 09, 08:52 AM Thread Starter
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Question Feul Percolating in tank!!

I got a new gas cap. The old one leaked fuel when I mashed the pedal and the gas sloshed backward, it wasn't sealing properly.

Now after driving the car I hear what sounds softly like a kettle. I open the gas kap and the built up pressure escapes and the noise is gone.

My Flowmaster transverse muffler is cooking the fuel inthe tank!! This is a little concerning does anyone have a similar experience and how worried should I be about the boiling gas in the tank. Could it explode?

John

69 Coupe: Forged Hydraulic Roller 383, Holley HP 750 DP, AFR195s, RPM Air Gap, Borg Warner T-56, Hooker Super Comp 1.75", Ford 9" with custom Moser axels, 3.89 Posi, MSD digital 6, Hotchkis springs, 4WDB, [email protected] on bald Nitto 555's
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post #2 of 14 (permalink) Old Sep 16th, 09, 09:38 AM
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Re: Feul Percolating in tank!!

No problem. Have the hazmat truck follow you.

You might want to put a insulation pad between the muffler and tank.
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post #3 of 14 (permalink) Old Sep 16th, 09, 10:45 AM Thread Starter
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Re: Feul Percolating in tank!!

Quote:
Originally Posted by parkbrau View Post
No problem. Have the hazmat truck follow you.

You might want to put a insulation pad between the muffler and tank.

Yeah I was thinking more like Fire Department. Would dynamat work or is that more for interiors. I wonder what type of heat barrier would work. There is a heat shield on the muffler but it obviously needs more

I have even considered going with duals and tossing the transverse. I do like the ground clearance though.

John

69 Coupe: Forged Hydraulic Roller 383, Holley HP 750 DP, AFR195s, RPM Air Gap, Borg Warner T-56, Hooker Super Comp 1.75", Ford 9" with custom Moser axels, 3.89 Posi, MSD digital 6, Hotchkis springs, 4WDB, [email protected] on bald Nitto 555's
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post #4 of 14 (permalink) Old Sep 16th, 09, 11:16 AM
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Re: Feul Percolating in tank!!

Do you have turn downs? Your tank may be letting air in but not letting air escape. As the tank heats up it needs room to expend. Vented caps will only let atmospheric pressure in the tank to replace burnt fuel.
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post #5 of 14 (permalink) Old Sep 16th, 09, 11:24 AM Thread Starter
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Re: Feul Percolating in tank!!

Quote:
Originally Posted by Vegas69 View Post
Do you have turn downs? Your tank may be letting air in but not letting air escape. As the tank heats up it needs room to expend. Vented caps will only let atmospheric pressure in the tank to replace burnt fuel.


It's definately not letting air escape. Turndowns?? I'm not quite sure what you are reffering to.

John

69 Coupe: Forged Hydraulic Roller 383, Holley HP 750 DP, AFR195s, RPM Air Gap, Borg Warner T-56, Hooker Super Comp 1.75", Ford 9" with custom Moser axels, 3.89 Posi, MSD digital 6, Hotchkis springs, 4WDB, [email protected] on bald Nitto 555's
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post #6 of 14 (permalink) Old Sep 16th, 09, 12:03 PM
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Re: Feul Percolating in tank!!

John, your cap is working perfectly. 69 caps let air in, not out. So they whoose when opened. Relax. But cooling your tank is always a good thing. And hearing a leak before the cap is removed is not good. It shouldn't make a sound.
Another thing; always open the cap before cracking open the fuel system. Don't ask.

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post #7 of 14 (permalink) Old Sep 16th, 09, 01:53 PM Thread Starter
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Re: Feul Percolating in tank!!

Quote:
Originally Posted by Fred Ficarra View Post
John, your cap is working perfectly. 69 caps let air in, not out. So they whoose when opened. Relax. But cooling your tank is always a good thing. And hearing a leak before the cap is removed is not good. It shouldn't make a sound.
Another thing; always open the cap before cracking open the fuel system. Don't ask.

I thought the cap was good, its brand new. The old cap didn't seal and was letting out the fumes into the garage. But now after a drive when everything is hot and under pressure the gas can be heard bubbling away, its a little un-nerving. After I open the cap to relieve the pressure it stops percolating.

John

69 Coupe: Forged Hydraulic Roller 383, Holley HP 750 DP, AFR195s, RPM Air Gap, Borg Warner T-56, Hooker Super Comp 1.75", Ford 9" with custom Moser axels, 3.89 Posi, MSD digital 6, Hotchkis springs, 4WDB, [email protected] on bald Nitto 555's
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post #8 of 14 (permalink) Old Sep 16th, 09, 02:19 PM
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Re: Feul Percolating in tank!!

And you are sure it is a vented cap right? If you create a vacuum (non-vented cap) in the tank, you lower the boiling point of a liquid.

alan
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post #9 of 14 (permalink) Old Sep 16th, 09, 02:26 PM
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Re: Feul Percolating in tank!!

Are you running full exhaust or do your mufflers have turn downs to keep the exhaust off the tank?
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post #10 of 14 (permalink) Old Sep 16th, 09, 03:02 PM Thread Starter
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Re: Feul Percolating in tank!!

Quote:
Originally Posted by alanrw View Post
And you are sure it is a vented cap right? If you create a vacuum (non-vented cap) in the tank, you lower the boiling point of a liquid.

alan
Fred says the vented caps are suposed to let air in not out. There is definately pressure in the tank that relieves itself when the cap is removed. I suppose the higher pressure in the tank lowers the boiling piont

Quote:
Originally Posted by Vegas69 View Post
Are you running full exhaust or do your mufflers have turn downs to keep the exhaust off the tank?
I thought you were referring to the exhaust but wasn't sure. My exhaust exits the rear. If you look on my name and check out my profile I think you can see the tips in the picture of my car. The transverse muffler mounts sideways between the rear diff and the gas tank and I guess it gets hot enough to expand the vapours in the tank and boil the gas.

John

69 Coupe: Forged Hydraulic Roller 383, Holley HP 750 DP, AFR195s, RPM Air Gap, Borg Warner T-56, Hooker Super Comp 1.75", Ford 9" with custom Moser axels, 3.89 Posi, MSD digital 6, Hotchkis springs, 4WDB, [email protected] on bald Nitto 555's
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post #11 of 14 (permalink) Old Sep 16th, 09, 03:08 PM
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Re: Feul Percolating in tank!!

Shoot the tank, next to the muffler, with a temperature gun to see how hot it is getting to 'percolate' the fuel.

As said, the tank will get warm due to the exhaust, engine heat, trans heat, and road heat, if ambient temp warrants it.

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post #12 of 14 (permalink) Old Sep 16th, 09, 03:59 PM
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Re: Feul Percolating in tank!!

Well, actually, increasing pressure increases the boiling point. Decreasing pressure lowers the BP, that's why it takes longer to cook food in the Rockies compared to Santa Monica. If you have a non vented cap and you develop a vacuum in the tank due to the fuel pump, it will lower the BP of gas. Of course, if it is indeed a non vented cap, after a while, the car will quit due to fuel starvation.

As Everett says, check the temp of the tank by the muffler.

alan
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post #13 of 14 (permalink) Old Sep 16th, 09, 04:28 PM
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Re: Feul Percolating in tank!!

Yep, you can just use you hand for a guesstimate. When I had a cross flow, (two of them actually) I was worried about heat. But I don't remember boiling the fuel. If it seems too warm for your liking, loose the cross flow. It's your call.
Maybe something like this will pull your chain;

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TH400 (CX) with Coan 8" converter, GV-OD, 8 track still on console and best et 10.495,
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128.79mph 1.428 60'
All with 1960's stuff. (except tires and converter)
+ MT Super Scavenger headers & 3" full exhaust with X pipe. 3700 lbs. with me in it.
1000cfm AED and HD Harold-Lunati SR, 725 lift with shaft rockers too.
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post #14 of 14 (permalink) Old Sep 17th, 09, 07:29 AM Thread Starter
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Re: Feul Percolating in tank!!

Thanks for all the replies. I may loose the crossflow or try to insulate the tank a bit. I like the sound of the muffler and the extra ground clearance. I just don't think boiling the gas is a good thing. Not only will the fuel feeding the carb be hot but its scary boiling the gas. I know it probably isn't too dangerous and that a spark is required for combustion but I find myself opening the cap to relieve the pressure every time I've go for a drive.


John

69 Coupe: Forged Hydraulic Roller 383, Holley HP 750 DP, AFR195s, RPM Air Gap, Borg Warner T-56, Hooker Super Comp 1.75", Ford 9" with custom Moser axels, 3.89 Posi, MSD digital 6, Hotchkis springs, 4WDB, [email protected] on bald Nitto 555's
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